John C. Moore

Abstract. Many scientists have made use of the wavelet method in analyzing time series, often using popular free software. However, at present there are no similar easy to use wavelet packages for analyzing two time series together. We discuss the cross wavelet transform and wavelet coherence for examining relationships in time frequency space between two time series. We demonstrate how phase angle statistics can be used to gain confidence in causal relationships and test mechanistic models of physical relationships between the time series. As an example of typical data where such analyses have proven useful, we apply the methods to the Arctic Oscillation index and the Baltic maximum sea ice extent record. Monte Carlo methods are used to assess the statistical significance against red noise backgrounds. A software package has been developed that allows users to perform the cross wavelet transform and wavelet coherence (www.pol.ac.uk/home/research/waveletcoherence/).

Abstract Traditional approaches to the study of food webs emphasize the transfer of local primary productivity in the form of living plant organic matter across trophic levels. However, dead organic matter, or detritus, a common feature of most ecosystems plays a frequently overlooked role as a dynamic heterogeneous resource and habitat for many species. We develop an integrative framework for understanding the impact of detritus that emphasizes the ontogeny and heterogeneity of detritus and the various ways that explicit inclusion of detrital dynamics alters generalizations about the structure and functioning of food webs. Through its influences on food web composition and dynamics, detritus often increases system stability and persistence, having substantial effects on trophic structure and biodiversity. Inclusion of detrital heterogeneity in models of food web dynamics is an essential new direction for ecological research.

Ecology Letters (2010) 13: 394–407 Abstract Mycorrhizal fungi influence plant growth, local biodiversity and ecosystem function. Effects of the symbiosis on plants span the continuum from mutualism to parasitism. We sought to understand this variation in symbiotic function using meta‐analysis with information theory‐based model selection to assess the relative importance of factors in five categories: (1) identity of the host plant and its functional characteristics, (2) identity and type of mycorrhizal fungi (arbuscular mycorrhizal vs. ectomycorrhizal), (3) soil fertility, (4) biotic complexity of the soil and (5) experimental location (laboratory vs. field). Across most subsets of the data, host plant functional group and N‐fertilization were surprisingly much more important in predicting plant responses to mycorrhizal inoculation (‘plant response’) than other factors. Non‐N‐fixing forbs and woody plants and C 4 grasses responded more positively to mycorrhizal inoculation than plants with N‐fixing bacterial symbionts and C 3 grasses. In laboratory studies of the arbuscular mycorrhizal symbiosis, plant response was more positive when the soil community was more complex. Univariate analyses supported the hypothesis that plant response is most positive when plants are P‐limited rather than N‐limited. These results emphasize that mycorrhizal function depends on both abiotic and biotic context, and have implications for plant community theory and restoration ecology.

The prevalence of diabetes mellitus is growing at epidemic proportions in the United States and worldwide. Most alarming is the steady increase in type 2 diabetes, especially among young and obese people. An estimated 7% of the US population has diabetes, and because of the increased longevity of this population, diabetes-associated complications are expected to rise in prevalence. Foot ulcerations, infections, Charcot neuroarthropathy, and peripheral arterial disease frequently result in gangrene and lower limb amputation. Consequently, foot disorders are leading causes of hospitalization for persons with diabetes and account for billion-dollar expenditures annually in the US. Although not all foot complications can be prevented, dramatic reductions in frequency have been achieved by taking a multidisciplinary approach to patient management. Using this concept, the authors present a clinical practice guideline for diabetic foot disorders based on currently available evidence, committee consensus, and current clinical practice. The pathophysiology and treatment of diabetic foot ulcers, infections, and the diabetic Charcot foot are reviewed. While these guidelines cannot and should not dictate the care of all affected patients, they provide evidence-based guidance for general patterns of practice. If these concepts are embraced and incorporated into patient management protocols, a major reduction in diabetic limb amputations is certainly an attainable goal.

Ecologists have long been studying stability in ecosystems by looking at the structuring and the strengths of trophic interactions in community food webs. In a series of real food webs from native and agricultural soils, the strengths of the interactions were found to be patterned in a way that is important to ecosystem stability. The patterning consisted of the simultaneous occurrence of strong "top down" effects at lower trophic levels and strong "bottom up" effects at higher trophic levels. As the patterning resulted directly from the energetic organization of the food webs, the results show that energetics and community structure govern ecosystem stability by imposing stabilizing patterns of interaction strengths.

With a growing world population and increasingly demanding consumers, the production of sufficient protein from livestock, poultry, and fish represents a serious challenge for the future. Approximately 1,900 insect species are eaten worldwide, mainly in ...Read More

Several leaf litter decay studies have indicated that decomposition occurs more rapidly when litter is placed beneath the plant species from which it had been derived than beneath a different plant species (i.e. home-field advantage, HFA), although support for this notion has not been universal. We provide the first quantification of HFA in relation to leaf litter decomposition using published litter mass loss data from forest ecosystems in North America, South America, and Europe. Our findings indicate that HFA is widespread in forest ecosystems; on average litter mass loss was 8% faster at home than away. We hypothesize that HFA results from specialization of the soil biotic community in decomposing litter derived from the plant above it. Climate and initial litter quality data can be used to explain about 70% of the variability in litter decomposition at a global scale, leaving about 30% unexplained. We suggest that HFA be recognized as a factor that explains some of this remaining variability.

We present a reconstruction of global sea level (GSL) since 1700 calculated from tide gauge records and analyse the evolution of global sea level acceleration during the past 300 years. We provide observational evidence that sea level acceleration up to the present has been about 0.01 mm/yr 2 and appears to have started at the end of the 18th century. Sea level rose by 6 cm during the 19th century and 19 cm in the 20th century. Superimposed on the long‐term acceleration are quasi‐periodic fluctuations with a period of about 60 years. If the conditions that established the acceleration continue, then sea level will rise 34 cm over the 21st century. Long time constants in oceanic heat content and increased ice sheet melting imply that the latest Intergovernmental Panel on Climate Change (IPCC) estimates of sea level are probably too low.

Variability in time series of ice conditions in the Baltic Sea is examined within the context of atmospheric circulation represented by the North Atlantic Oscillation (NAO) and Arctic Oscillation (AO) winter indices using the wavelet approach. We develop methods of assessing statistical significance and confidence intervals of cross‐wavelet phase and wavelet coherence. Cross‐wavelet power for the time series indicates that the times of largest variance in ice conditions are in excellent agreement with significant power in the AO at 2.2–3.5, 5.7–7.8, and 12–20 year periods, similar patterns are also seen with the Southern Oscillation Index (SOI) and Niño3 sea surface temperature (Niño3) series. Wavelet coherence shows in‐phase linkages between the 2.2–7.8 and 12–20 year period signals in both tropical and Arctic atmospheric circulation and also with ice conditions in the Baltic Sea. These results are consistent with GCM simulations showing dynamical connections between high‐latitude surface conditions, tropical sea surface temperatures mediated by tropical wave propagation, the wintertime polar vortex, and the AO and with models of sea ice and oceanic feedbacks at decadal periods.

Climate change and its social, environmental, economic and ethical consequences are widely recognized as the major set of interconnected problems facing human societies. Its impacts and costs will be large, serious, and unevenly spread, globally for decades. The main factor causing climate change and global warming is the increase of global carbon emissions produced by human activities such as deforestation and burning of fossil fuels. In this special volume, the articles mainly focus on investigations of technical innovations and policy interventions for improved energy efficiency and carbon emissions reduction in a wide diversity of industrial, construction and agricultural sectors at different scales, from the smallest scales (firm or household), cities, regional, to national and global scales. Some articles in this special volume assess alternative carbon emissions reduction approaches, such as carbon capture and storage and geoengineering schemes. Given the high cost and internal/external uncertainties of carbon capture and storage and risks and side effects of various geoengineering schemes, improved energy efficiency and widespread implementation of low fossil-carbon renewable-energy based systems are clearly the most direct and effective approaches to reduce carbon emissions. This means that we have to radically transform our societal metabolism towards low/no fossil-carbon economies. However, design and implementation of low/no fossil-carbon production will require fundamental changes in the design, production and use of products and these needed changes are evolving but much more needs to be done. Additionally, the design and timing of suitable climate policy interventions, such as various carbon taxation/trading schemes, must be integral in facilitating the development of low fossil carbon products and accelerating the transition to post-fossil carbon societies.

We analyze the Permanent Service for Mean Sea Level (PSMSL) database of sea level time series using a method based on Monte Carlo Singular Spectrum Analysis (MC‐SSA). We remove 2–30 year quasi‐periodic oscillations and determine the nonlinear long‐term trends for 12 large ocean regions. Our global sea level trend estimate of 2.4 ± 1.0 mm/yr for the period from 1993 to 2000 is comparable with the 2.6 ± 0.7 mm/yr sea level rise calculated from TOPEX/Poseidon altimeter measurements. However, we show that over the last 100 years the rate of 2.5 ± 1.0 mm/yr occurred between 1920 and 1945, is likely to be as large as the 1990s, and resulted in a mean sea level rise of 48 mm. We evaluate errors in sea level using two independent approaches, the robust bi‐weight mean and variance, and a novel “virtual station” approach that utilizes geographic locations of stations. Results suggest that a region cannot be adequately represented by a simple mean curve with standard error, assuming all stations are independent, as multiyear cycles within regions are very significant. Additionally, much of the between‐region mismatch errors are due to multiyear cycles in the global sea level that limit the ability of simple means to capture sea level accurately. We demonstrate that variability in sea level records over periods 2–30 years has increased during the past 50 years in most ocean basins.

We conducted a model-based assessment of changes in permafrost area and carbon storage for simulations driven by RCP4.5 and RCP8.5 projections between 2010 and 2299 for the northern permafrost region. All models simulating carbon represented soil with depth, a critical structural feature needed to represent the permafrost carbon-climate feedback, but that is not a universal feature of all climate models. Between 2010 and 2299, simulations indicated losses of permafrost between 3 and 5 million km2 for the RCP4.5 climate and between 6 and 16 million km2 for the RCP8.5 climate. For the RCP4.5 projection, cumulative change in soil carbon varied between 66-Pg C (1015-g carbon) loss to 70-Pg C gain. For the RCP8.5 projection, losses in soil carbon varied between 74 and 652 Pg C (mean loss, 341 Pg C). For the RCP4.5 projection, gains in vegetation carbon were largely responsible for the overall projected net gains in ecosystem carbon by 2299 (8- to 244-Pg C gains). In contrast, for the RCP8.5 projection, gains in vegetation carbon were not great enough to compensate for the losses of carbon projected by four of the five models; changes in ecosystem carbon ranged from a 641-Pg C loss to a 167-Pg C gain (mean, 208-Pg C loss). The models indicate that substantial net losses of ecosystem carbon would not occur until after 2100. This assessment suggests that effective mitigation efforts during the remainder of this century could attenuate the negative consequences of the permafrost carbon-climate feedback.

Abstract Solar geoengineering—deliberate reduction in the amount of solar radiation retained by the Earth—has been proposed as a means of counteracting some of the climatic effects of anthropogenic greenhouse gas emissions. We present results from Experiment G1 of the Geoengineering Model Intercomparison Project, in which 12 climate models have simulated the climate response to an abrupt quadrupling of CO 2 from preindustrial concentrations brought into radiative balance via a globally uniform reduction in insolation. Models show this reduction largely offsets global mean surface temperature increases due to quadrupled CO 2 concentrations and prevents 97% of the Arctic sea ice loss that would otherwise occur under high CO 2 levels but, compared to the preindustrial climate, leaves the tropics cooler (−0.3 K) and the poles warmer (+0.8 K). Annual mean precipitation minus evaporation anomalies for G1 are less than 0.2 mm day −1 in magnitude over 92% of the globe, but some tropical regions receive less precipitation, in part due to increased moist static stability and suppression of convection. Global average net primary productivity increases by 120% in G1 over simulated preindustrial levels, primarily from CO 2 fertilization, but also in part due to reduced plant heat stress compared to a high CO 2 world with no geoengineering. All models show that uniform solar geoengineering in G1 cannot simultaneously return regional and global temperature and hydrologic cycle intensity to preindustrial levels.

Abstract. An earth system model has been developed at Beijing Normal University (Beijing Normal University Earth System Model, BNU-ESM); the model is based on several widely evaluated climate model components and is used to study mechanisms of ocean-atmosphere interactions, natural climate variability and carbon-climate feedbacks at interannual to interdecadal time scales. In this paper, the model structure and individual components are described briefly. Further, results for the CMIP5 (Coupled Model Intercomparison Project phase 5) pre-industrial control and historical simulations are presented to demonstrate the model's performance in terms of the mean model state and the internal variability. It is illustrated that BNU-ESM can simulate many observed features of the earth climate system, such as the climatological annual cycle of surface-air temperature and precipitation, annual cycle of tropical Pacific sea surface temperature (SST), the overall patterns and positions of cells in global ocean meridional overturning circulation. For example, the El Niño-Southern Oscillation (ENSO) simulated in BNU-ESM exhibits an irregular oscillation between 2 and 5 years with the seasonal phase locking feature of ENSO. Important biases with regard to observations are presented and discussed, including warm SST discrepancies in the major upwelling regions, an equatorward drift of midlatitude westerly wind bands, and tropical precipitation bias over the ocean that is related to the double Intertropical Convergence Zone (ITCZ).

[1] The hydrological impact of enhancing Earth's albedo by solar radiation management is investigated using simulations from 12 Earth System models contributing to the Geoengineering Model Intercomparison Project (GeoMIP). We contrast an idealized experiment, G1, where the global mean radiative forcing is kept at preindustrial conditions by reducing insolation while the CO2 concentration is quadrupled to a 4×CO2 experiment. The reduction of evapotranspiration over land with instantaneously increasing CO2 concentrations in both experiments largely contributes to an initial reduction in evaporation. A warming surface associated with the transient adjustment in 4×CO2 generates an increase of global precipitation by around 6.9% with large zonal and regional changes in both directions, including a precipitation increase of 10% over Asia and a reduction of 7% for the North American summer monsoon. Reduced global evaporation persists in G1 with temperatures close to preindustrial conditions. Global precipitation is reduced by around 4.5%, and significant reductions occur over monsoonal land regions: East Asia (6%), South Africa (5%), North America (7%), and South America (6%). The general precipitation performance in models is discussed in comparison to observations. In contrast to the 4×CO2 experiment, where the frequency of months with heavy precipitation intensity is increased by over 50% in comparison to the control, a reduction of up to 20% is simulated in G1. These changes in precipitation in both total amount and frequency of extremes point to a considerable weakening of the hydrological cycle in a geoengineered world.

Sea level rise over the coming centuries is perhaps the most damaging side of rising temperature (Anthoff et al., 2009). The economic costs and social consequences of coastal flooding and forced migration will probably be one of the dominant impacts of global warming (Sugiyama et al., 2008). To date, however, few studies (Nicholls et al., 2008; Anthoff et al., 2009) on infrastructure and socio-economic planning include provision for multi-century and multi-metre rises in mean sea level. Here we use a physically plausible sea level model constrained by observations, and forced with four new Representative Concentration Pathways (RCP) radiative forcing scenarios (Moss et al., 2010) to project median sea level rises of 0.57 for the lowest forcing and 1.10 m for the highest forcing by 2100 which rise to 1.84 and 5.49 m respectively by 2500. Sea level will continue to rise for several centuries even after stabilisation of radiative forcing with most of the rise after 2100 due to the long response time of sea level. The rate of sea level rise would be positive for centuries, requiring 200–400 years to drop to the 1.8 mm/yr 20th century average, except for the RCP3PD which would rely on geoengineering.

Iceberg calving from all Antarctic ice shelves has never been directly measured, despite playing a crucial role in ice sheet mass balance. Rapid changes to iceberg calving naturally arise from the sporadic detachment of large tabular bergs but can also be triggered by climate forcing. Here we provide a direct empirical estimate of mass loss due to iceberg calving and melting from Antarctic ice shelves. We find that between 2005 and 2011, the total mass loss due to iceberg calving of 755 ± 24 gigatonnes per year (Gt/y) is only half the total loss due to basal melt of 1516 ± 106 Gt/y. However, we observe widespread retreat of ice shelves that are currently thinning. Net mass loss due to iceberg calving for these ice shelves (302 ± 27 Gt/y) is comparable in magnitude to net mass loss due to basal melt (312 ± 14 Gt/y). Moreover, we find that iceberg calving from these decaying ice shelves is dominated by frequent calving events, which are distinct from the less frequent detachment of isolated tabular icebergs associated with ice shelves in neutral or positive mass balance regimes. Our results suggest that thinning associated with ocean-driven increased basal melt can trigger increased iceberg calving, implying that iceberg calving may play an overlooked role in the demise of shrinking ice shelves, and is more sensitive to ocean forcing than expected from steady state calving estimates.

Detection and attribution of past changes in cyclone activity are hampered by biased cyclone records due to changes in observational capabilities. Here, we relate a homogeneous record of Atlantic tropical cyclone activity based on storm surge statistics from tide gauges to changes in global temperature patterns. We examine 10 competing hypotheses using nonstationary generalized extreme value analysis with different predictors (North Atlantic Oscillation, Southern Oscillation, Pacific Decadal Oscillation, Sahel rainfall, Quasi-Biennial Oscillation, radiative forcing, Main Development Region temperatures and its anomaly, global temperatures, and gridded temperatures). We find that gridded temperatures, Main Development Region, and global average temperature explain the observations best. The most extreme events are especially sensitive to temperature changes, and we estimate a doubling of Katrina magnitude events associated with the warming over the 20th century. The increased risk depends on the spatial distribution of the temperature rise with highest sensitivity from tropical Atlantic, Central America, and the Indian Ocean. Statistically downscaling 21st century warming patterns from six climate models results in a twofold to sevenfold increase in the frequency of Katrina magnitude events for a 1 °C rise in global temperature (using BNU-ESM, BCC-CSM-1.1, CanESM2, HadGEM2-ES, INM-CM4, and NorESM1-M).

Global fire regimes are shifting due to climate and land use changes. Understanding the responses of belowground communities to fire is key to predicting changes in the ecosystem processes they regulate. We conducted a comprehensive meta‐analysis of 1634 observations from 131 empirical studies to investigate the effect of fire on soil microorganisms and mesofauna. Fire had a strong negative effect on soil biota biomass, abundance, richness, evenness, and diversity. Fire reduced microorganism biomass and abundance by up to 96%. Bacteria were more resistant to fire than fungi. Fire reduced nematode abundance by 88% but had no significant effect on soil arthropods. Fire reduced richness, evenness and diversity of soil microorganisms and mesofauna by up to 99%. We found little evidence of temporal trends towards recovery within 10 years post‐disturbance suggesting little resilience of the soil community to fire. Interactions between biome, fire type, and depth explained few of these negative trends. Future research at the intersection of fire ecology and soil biology should aim to integrate soil community structure with the ecosystem processes they mediate under changing global fire regimes.

We use 1277 tide gauge records since 1807 to provide an improved global sea level reconstruction and analyse the evolution of sea level trend and acceleration. In particular we use new data from the polar regions and remote islands to improve data coverage and extend the reconstruction to 2009. There is a good agreement between the rate of sea level rise (3.2 ± 0.4 mm·yr− 1) calculated from satellite altimetry and the rate of 3.1 ± 0.6 mm·yr− 1 from tide gauge based reconstruction for the overlapping time period (1993–2009). The new reconstruction suggests a linear trend of 1.9 ± 0.3 mm·yr− 1 during the 20th century, with 1.8 ± 0.5 mm·yr− 1 since 1970. Regional linear trends for 14 ocean basins since 1970 show the fastest sea level rise for the Antarctica (4.1 ± 0.8 mm·yr− 1) and Arctic (3.6 ± 0.3 mm·yr− 1). Choice of GIA correction is critical in the trends for the local and regional sea levels, introducing up to 8 mm·yr− 1 uncertainties for individual tide gauge records, up to 2 mm·yr− 1 for regional curves and up to 0.3–0.6 mm·yr− 1 in global sea level reconstruction. We calculate an acceleration of 0.02 ± 0.01 mm·yr− 2 in global sea level (1807–2009). In comparison the steric component of sea level shows an acceleration of 0.006 mm·yr− 2 and mass loss of glaciers accelerates at 0.003 mm·yr− 2 over 200 year long time series.

The pool of soil organic carbon (SOC) in the Arctic is disproportionally large compared to those in other biomes. This large quantity of SOC accumulated over millennia due to slow rates of decomposition relative to net primary productivity. Decomposition is constrained by low temperatures and nutrient concentrations, which limit soil microbial activity. We investigated how nutrients limit bacterial and fungal biomass and community composition in organic and mineral soils within moist acidic tussock tundra ecosystems. We sampled two experimental arrays of moist acidic tussock tundra that included fertilized and non-fertilized control plots. One array included plots that had been fertilized annually since 1989 and the other since 2006. Fertilization significantly altered overall bacterial community composition and reduced evenness, to a greater degree in organic than mineral soils, and in the 1989 compared to the 2006 site. The relative abundance of copiotrophic α-proteobacteria and β-proteobacteria was higher in fertilized than control soils, and oligotrophic Acidobacteria were less abundant in fertilized than control soils at the 1989 site. Fungal community composition was less sensitive to increased nutrient availability, and fungal responses to fertilization were not consistent between soil horizons and sites. We detected two ectomycorrhizal genera, Russula and Cortinarius spp., associated with shrubs. Their relative abundance was not affected by fertilization despite increased dominance of their host plants in the fertilized plots. Our results indicate that fertilization, which has been commonly used to simulate warming in Arctic tundra, has limited applicability for investigating fungal dynamics under warming.

Two degrees of global warming above the preindustrial level is widely suggested as an appropriate threshold beyond which climate change risks become unacceptably high. This "2 °C" threshold is likely to be reached between 2040 and 2050 for both Representative Concentration Pathway (RCP) 8.5 and 4.5. Resulting sea level rises will not be globally uniform, due to ocean dynamical processes and changes in gravity associated with water mass redistribution. Here we provide probabilistic sea level rise projections for the global coastline with warming above the 2 °C goal. By 2040, with a 2 °C warming under the RCP8.5 scenario, more than 90% of coastal areas will experience sea level rise exceeding the global estimate of 0.2 m, with up to 0.4 m expected along the Atlantic coast of North America and Norway. With a 5 °C rise by 2100, sea level will rise rapidly, reaching 0.9 m (median), and 80% of the coastline will exceed the global sea level rise at the 95th percentile upper limit of 1.8 m. Under RCP8.5, by 2100, New York may expect rises of 1.09 m, Guangzhou may expect rises of 0.91 m, and Lagos may expect rises of 0.90 m, with the 95th percentile upper limit of 2.24 m, 1.93 m, and 1.92 m, respectively. The coastal communities of rapidly expanding cities in the developing world, and vulnerable tropical coastal ecosystems, will have a very limited time after midcentury to adapt to sea level rises unprecedented since the dawn of the Bronze Age.

Abstract Stratospheric aerosol injection (SAI) has been shown in climate models to reduce some impacts of global warming in the Arctic, including the loss of sea ice, permafrost thaw, and reduction of Greenland Ice Sheet (GrIS) mass; SAI at high latitudes could preferentially target these impacts. In this study, we use the Community Earth System Model to simulate two Arctic‐focused SAI strategies, which inject at 60°N latitude each spring with injection rates adjusted to either maintain September Arctic sea ice at 2030 levels (“Arctic Low”) or restore it to 2010 levels (“Arctic High”). Both simulations maintain or restore September sea ice to within 10% of their respective targets, reduce permafrost thaw, and increase GrIS surface mass balance by reducing runoff. Arctic High reduces these impacts more effectively than a globally focused SAI strategy that injects similar quantities of SO 2 at lower latitudes. However, Arctic‐focused SAI is not merely a “reset button” for the Arctic climate, but brings about a novel climate state, including changes to the seasonal cycles of Northern Hemisphere temperature and sea ice and less high‐latitude carbon uptake relative to SSP2‐4.5. Additionally, while Arctic‐focused SAI produces the most cooling near the pole, its effects are not confined to the Arctic, including detectable cooling throughout most of the northern hemisphere for both simulations, increased mid‐latitude sulfur deposition, and a southward shift of the location of the Intertropical Convergence Zone. For these reasons, it would be incorrect to consider Arctic‐focused SAI as “local” geoengineering, even when compared to a globally focused strategy.

Food webs in conventional (high-input) and integrated (reduced-input) farming systems were simulated to estimate the contribution of soil microbes and soil fauna to nitrogen mineralization during the growing season. Microbes accounted for approximately 95% of the biomass and 70% of total nitrogen mineralization in both management practices. Among the soil fauna, amoebae and bacterivorous nematodes were the most important contributors to nitrogen mineralization. The contribution of nematodes showed more temporal and spatial variability than the contribution of amoebae. The model calculated nitrogen mineralization rates close to the observed rates for both fields and depth layers. In the integrated plot there were relatively high rates of mineralization in the 0-10 cm layer compared with the 10-25 cm layer, whereas in the conventional plot no differences were observed between depth layers (...)

EcologyVolume 84, Issue 4 p. 846-857 Special Feature TOP-DOWN IS BOTTOM-UP: DOES PREDATION IN THE RHIZOSPHERE REGULATE ABOVEGROUND DYNAMICS? John C. Moore, John C. Moore Department of Biological Sciences, University of Northern Colorado, Greeley, Colorado 80639 USA E-mail: john.moore@unco.eduSearch for more papers by this authorKevin McCann, Kevin McCann Department of Biology, McGill University, Montreal, Quebec, Canada H3A 1B1Search for more papers by this authorHeikki Setälä, Heikki Setälä Department of Ecological and Environmental Sciences, University of Helsinki, Niemenkatu 73, FIN 15140 Lahti, FinlandSearch for more papers by this authorPeter C. De Ruiter, Peter C. De Ruiter Department of Environmental Studies, University of Utretch, 3508 Utretch, The NetherlandsSearch for more papers by this author John C. Moore, John C. Moore Department of Biological Sciences, University of Northern Colorado, Greeley, Colorado 80639 USA E-mail: john.moore@unco.eduSearch for more papers by this authorKevin McCann, Kevin McCann Department of Biology, McGill University, Montreal, Quebec, Canada H3A 1B1Search for more papers by this authorHeikki Setälä, Heikki Setälä Department of Ecological and Environmental Sciences, University of Helsinki, Niemenkatu 73, FIN 15140 Lahti, FinlandSearch for more papers by this authorPeter C. De Ruiter, Peter C. De Ruiter Department of Environmental Studies, University of Utretch, 3508 Utretch, The NetherlandsSearch for more papers by this author First published: 01 April 2003 https://doi.org/10.1890/0012-9658(2003)084[0846:TIBDPI]2.0.CO;2Citations: 199 Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Abstract We explore two aspects of how predation within the rhizosphere influences nutrient availability, plant productivity, and aboveground community dynamics. First, plant roots and soil microbes have a long history of interaction that is centered on the reciprocal acquisition of carbon by microbes and nitrogen by plants. Predators within the rhizosphere alter these interactions in ways that benefit plants but also influence the dynamics of other species within ecosystems and processes that are important to ecosystem function and stability. These same predators regulate their prey in a traditional “top-down” manner but in doing so alter the release of nutrients that may limit plant productivity and thereby affect plant growth in a “bottom-up” fashion as well. Second, much attention has been given to the importance of specific interactions, or, as presented within this series, genes and/or gene products as critical control points. We suggest that control should be viewed within the framework of interactivity. The interdependence between the aboveground and belowground realms can be explained in terms of the patterning of trophic interactions within the rhizosphere and the influence of these interactions on the supply of nutrients and rates of nutrient uptake by plants. While specific interactions may be important, it is the patterning of these interactions into assemblages of species that share similar growth rates and habitats that is the salient feature of the rhizosphere that confers stability, affects nutrient retention, and regulates aboveground and belowground dynamics. Corresponding Editor: D. A. Phillips. For reprints of this Special Feature, see footnote 1, p. 815 Citing Literature Volume84, Issue4April 2003Pages 846-857 RelatedInformation

Soil communities are compartmentalized into pathways of trophic interactions and nutrient flows that originate from plant roots, bacteria and fungi. The pathways differ in terms of the organisms that comprise them, the habitats that the organisms occupy and the rates by which the organisms process and transfer material and energy. The fungi, nematodes and arthropods within the fungal pathway live in air-filled pore spaces and water films, while the bacteria, protozoa, and nematodes within the bacterial pathway occupy water-filled pore spaces and water films. Organisms within the fungal pathway have longer generation times and process matter at slower rates than those within the bacterial pathway. Empirical studies have shown that under natural conditions the pathways co-exist in a stable manner. The relative sizes (indexed by the densities of organisms) and activities (indexed by nutrient-flow rates, excretion rates and respiration rates) of the pathways may change seasonally and in response to minor disturbances, but they persist. However, large anthropogenic and natural disturbances induce shifts in the relative sizes and activities of the pathways. Coincident with these shifts are reports of changes in the aboveground plant community and the availability and retention of plant limiting nutrients. We developed simple models of the bacterial and fungal pathways to explore the consequences of the observed shifts on the dynamic stability of the system. The more stable configurations occurred when there was a balance in the flow of nutrients between the two pathways. Large shifts in nutrient cycling and community structure towards either the fungal pathway or toward the bacterial pathway resulted in less stable or unstable configurations.

Ecologists have long searched for structures and processes that impart stability in nature. In particular, food web ecology has held promise in tackling this issue. Empirical patterns in food webs have consistently shown that the distributions of species and interactions in nature are more likely to be stable than randomly constructed systems with the same number of species and interactions. Food web ecology still faces two fundamental challenges, however. First, the quantity and quality of food web data required to document both the species richness and the interaction strengths among all species within food webs is largely prohibitive. Second, where food webs have been well documented, spatial and temporal variation in food web structure has been ignored. Conversely, research that has addressed spatial and temporal variation in ecosystems has generally ignored the full complexity of food web architecture. Here, we incorporate empirical patterns, largely from macroecology and behavioural ecology, into a spatially implicit food web structure to construct a simple landscape theory of food web architecture. Such an approach both captures important architectural features of food webs and allows for an exploration of food web structure across a range of spatial scales. Finally, we demonstrated that food webs are hierarchically organized along the spatial and temporal niche axes of species and their utilization of food resources in ways that stabilize ecosystems.

Soil biodiversity has received con- siderable attention recently because of greater

Using an inverse statistical model we examine potential response in sea level to the changes in natural and anthropogenic forcings by 2100. With six IPCC radiative forcing scenarios we estimate sea level rise of 0.6–1.6 m, with confidence limits of 0.59 m and 1.8 m. Projected impacts of solar and volcanic radiative forcings account only for, at maximum, 5% of total sea level rise, with anthropogenic greenhouse gasses being the dominant forcing. As alternatives to the IPCC projections, even the most intense century of volcanic forcing from the past 1000 years would result in 10–15 cm potential reduction of sea level rise. Stratospheric injections of SO 2 equivalent to a Pinatubo eruption every 4 years would effectively just delay sea level rise by 12–20 years. A 21st century with the lowest level of solar irradiance over the last 9300 years results in negligible difference to sea level rise.

The lengths of food chains within ecosystems have been thought to be limited either by the productivity of the ecosystem or by the resilience of that ecosystem after perturbation. Models based on ecological energetics that follow the form of Lotka-Volterra equations and equations that include material (detritus) recycling show that productivity and resilience are inextricably interrelated. The models were initialized with data from 5- to 10-year studies of actual soil food webs. Estimates indicate that most ecological production worldwide is from ecosystems that are themselves sufficiently productive to recover from minor perturbations.

Real food webs are dynamic multi-dimensional systems, whereas the descriptions of real food webs often do not capture this complexity in that they have been confined to a single habitat (the community web sensu Cohen, 1978) and do not represent changes in time (Paine, 1988). We present an analytical approach that uses univariate and multivariate statistics and simulation modeling to study pattern within food webs. As an illustration of the approach, we compared below-ground food webs from natural and agricultural ecosystems in terms of their architecture, temporal dynamics of the biomass of functional groups, and the temporal and spatial dynamics of energy channels. The complexity and diversity of below-ground food webs are similar to the detritus-based food webs of other terrestrial and aquatic habitats. The pattern of the flow of nitrogen through the below-ground food webs of the Shortgrass Steppe of North America is similar to that of the food web of agricultural soils of reclaimed marine sediments in The Netherlands. The webs are compartmented along dominant flows of energy (energy channels) originating from primary production and detritus. Comparisons of the connectedness descriptions, and implementations of cluster analysis, canonical discriminant analysis and analysis of variance of temporal biomass of functional groups within food webs of soils from North America and The Netherlands, indicate that the detritus energy channel can be further compartmented into a fungal and bacterial channel. For winter wheat soils in The Netherlands, the degree of compartmentalization appears to depend on management practice. Consumers of fungi were separated in time from consumers of bacteria in the integrated management practice, while little separation was observed in conventional practice. Our study indicates (1) that analyses of food webs should aim to project the web onto the principal niche dimensions food, habitat and time, and (2) that quantitative measures of community structure — identification of functional groups, the biomass and productivity of functional groups, and the flow of nutrients within energy channels — are useful measures of food web structure.

De Ruiter et al. argue that the old notion of a food web as a static arch, with a critical keystone species (whose removal would cause collapse of the arch), is outdated. Instead, they see ecosystems as dynamic, both spatially and temporally, and explain how describing them in this way reveals the basis of unexpected stabilities that occur in response to even large environmental perturbations.

This 12-week, prospective, randomised, controlled multi-centre study compared the proportion of healed diabetic foot ulcers and mean healing time between patients receiving acellular matrix (AM) (study group) and standard of care (control group) therapies. Eighty-six patients were randomised into study (47 patients) and control (39 patients) groups. No significant differences in demographics or pre-treatment ulcer data were calculated. Complete healing and mean healing time were 69.6% and 5.7 weeks, respectively, for the study group and 46.2% and 6.8 weeks, respectively, for the control group. The proportion of healed ulcers between the groups was statistically significant (P = 0.0289), with odds of healing in the study group 2.7 times higher than in the control group. Kaplan-Meier survivorship analysis for time to complete healing at 12 weeks showed a significantly higher non healing rate (P = 0.015) for the control group (53.9%) compared with the study group (30.4%). After adjusting for ulcer size at presentation, which was a statistically significant covariate (P = 0.0194), a statistically significant difference in non healing rate between groups was calculated (P = 0.0233), with odds of healing 2.0 times higher in the study versus control group. This study supports the use of single-application AM therapy as an effective treatment of diabetic, neuropathic ulcers.

We construct the probability density function of global sea level at 2100, estimating that sea level rises larger than 180 cm are less than 5% probable. An upper limit for global sea level rise of 190 cm is assembled by summing the highest estimates of individual sea level rise components simulated by process based models with the RCP8.5 scenario. The agreement between the methods may suggest more confidence than is warranted since large uncertainties remain due to the lack of scenario-dependent projections from ice sheet dynamical models, particularly for mass loss from marine-based fast flowing outlet glaciers in Antarctica. This leads to an intrinsically hard to quantify fat tail in the probability distribution for global mean sea level rise. Thus our low probability upper limit of sea level projections cannot be considered definitive. Nevertheless, our upper limit of 180 cm for sea level rise by 2100 is based on both expert opinion and process studies and hence indicates that other lines of evidence are needed to justify a larger sea level rise this century.

We have examined changes in climate which result from the sudden termination of geoengineering after 50 years of offsetting a 1% per annum increase in CO 2 concentrations by a reduction of solar radiation, as simulated by 11 different climate models in experiment G2 of the Geoengineering Model Intercomparison Project. The models agree on a rapid increase in global‐mean temperature following termination accompanied by increases in global‐mean precipitation rate and decreases in sea‐ice cover. There is no agreement on the impact of geoengineering termination on the rate of change of global‐mean plant net primary productivity. There is a considerable degree of consensus for the geographical distribution of temperature change following termination, with faster warming at high latitudes and over land. There is also considerable agreement regarding the distribution of reductions in Arctic sea‐ice, but less so for the Antarctic. There is much less agreement regarding the patterns of change in precipitation and net primary productivity, with a greater degree of consensus at higher latitudes.

<strong class="journal-contentHeaderColor">Abstract.</strong> We present a suite of new climate model experiment designs for the Geoengineering Model Intercomparison Project (GeoMIP). This set of experiments, named GeoMIP6 (to be consistent with the Coupled Model Intercomparison Project Phase 6), builds on the previous GeoMIP project simulations, and has been expanded to address several further important topics, including key uncertainties in extreme events, the use of geoengineering as part of a portfolio of responses to climate change, and the relatively new idea of cirrus cloud thinning to allow more longwave radiation to escape to space. We discuss experiment designs, as well as the rationale for those designs, showing preliminary results from individual models when available. We also introduce a new feature, called the GeoMIP Testbed, which provides a platform for simulations that will be performed with a few models and subsequently assessed to determine whether the proposed experiment designs will be adopted as core (Tier 1) GeoMIP experiments. This is meant to encourage various stakeholders to propose new targeted experiments that address their key open science questions, with the goal of making GeoMIP more relevant to a broader set of communities.

Typically 20–40 extreme cyclone events (sometimes called 'weather bombs') occur in the Arctic North Atlantic per winter season, with an increasing trend of 6 events/decade over 1979–2015, according to 6 hourly station data from Ny-Ålesund. This increased frequency of extreme cyclones is consistent with observed significant winter warming, indicating that the meridional heat and moisture transport they bring is a factor in rising temperatures in the region. The winter trend in extreme cyclones is dominated by a positive monthly trend of about 3–4 events/decade in November–December, due mainly to an increasing persistence of extreme cyclone events. A negative trend in January opposes this, while there is no significant trend in February. We relate the regional patterns of the trend in extreme cyclones to anomalously low sea-ice conditions in recent years, together with associated large-scale atmospheric circulation changes such as 'blockinglike' circulation patterns (e.g. Scandinavian blocking in December and Ural blocking during January–February).

At the United Nations Framework Convention on Climate Change Conference in Cancun, in November 2010, the Heads of State reached an agreement on the aim of limiting the global temperature rise to 2 °C relative to preindustrial levels. They recognized that long-term future warming is primarily constrained by cumulative anthropogenic greenhouse gas emissions, that deep cuts in global emissions are required, and that action based on equity must be taken to meet this objective. However, negotiations on emission reduction among countries are increasingly fraught with difficulty, partly because of arguments about the responsibility for the ongoing temperature rise. Simulations with two earth-system models (NCAR/CESM and BNU-ESM) demonstrate that developed countries had contributed about 60–80%, developing countries about 20–40%, to the global temperature rise, upper ocean warming, and sea-ice reduction by 2005. Enacting pledges made at Cancun with continuation to 2100 leads to a reduction in global temperature rise relative to business as usual with a 1/3–2/3 (CESM 33–67%, BNU-ESM 35–65%) contribution from developed and developing countries, respectively. To prevent a temperature rise by 2 °C or more in 2100, it is necessary to fill the gap with more ambitious mitigation efforts.

Global-scale solar geoengineering is the deliberate modification of the climate system to offset some amount of anthropogenic climate change by reducing the amount of incident solar radiation at the surface. These changes to the planetary energy budget result in differential regional climate effects. For the first time, we quantitatively evaluate the potential for regional disparities in a multi-model context using results from a model experiment that offsets the forcing from a quadrupling of CO2 via reduction in solar irradiance. We evaluate temperature and precipitation changes in 22 geographic regions spanning most of Earth's continental area. Moderate amounts of solar reduction (up to 85% of the amount that returns global mean temperatures to preindustrial levels) result in regional temperature values that are closer to preindustrial levels than an un-geoengineered, high CO2 world for all regions and all models. However, in all but one model, there is at least one region for which no amount of solar reduction can restore precipitation toward its preindustrial value. For most metrics considering simultaneous changes in both variables, temperature and precipitation values in all regions are closer to the preindustrial climate for a moderate amount of solar reduction than for no solar reduction.

Abstract A significant portion of the large amount of carbon (C) currently stored in soils of the permafrost region in the Northern Hemisphere has the potential to be emitted as the greenhouse gases CO 2 and CH 4 under a warmer climate. In this study we evaluated the variability in the sensitivity of permafrost and C in recent decades among land surface model simulations over the permafrost region between 1960 and 2009. The 15 model simulations all predict a loss of near‐surface permafrost (within 3 m) area over the region, but there are large differences in the magnitude of the simulated rates of loss among the models (0.2 to 58.8 × 10 3 km 2 yr −1 ). Sensitivity simulations indicated that changes in air temperature largely explained changes in permafrost area, although interactions among changes in other environmental variables also played a role. All of the models indicate that both vegetation and soil C storage together have increased by 156 to 954 Tg C yr −1 between 1960 and 2009 over the permafrost region even though model analyses indicate that warming alone would decrease soil C storage. Increases in gross primary production (GPP) largely explain the simulated increases in vegetation and soil C. The sensitivity of GPP to increases in atmospheric CO 2 was the dominant cause of increases in GPP across the models, but comparison of simulated GPP trends across the 1982–2009 period with that of a global GPP data set indicates that all of the models overestimate the trend in GPP. Disturbance also appears to be an important factor affecting C storage, as models that consider disturbance had lower increases in C storage than models that did not consider disturbance. To improve the modeling of C in the permafrost region, there is the need for the modeling community to standardize structural representation of permafrost and carbon dynamics among models that are used to evaluate the permafrost C feedback and for the modeling and observational communities to jointly develop data sets and methodologies to more effectively benchmark models.

Detection and attribution of past changes in cyclone activity are hampered by biased cyclone records due to changes in observational capabilities. Here we construct an independent record of Atlantic tropical cyclone activity on the basis of storm surge statistics from tide gauges. We demonstrate that the major events in our surge index record can be attributed to landfalling tropical cyclones; these events also correspond with the most economically damaging Atlantic cyclones. We find that warm years in general were more active in all cyclone size ranges than cold years. The largest cyclones are most affected by warmer conditions and we detect a statistically significant trend in the frequency of large surge events (roughly corresponding to tropical storm size) since 1923. In particular, we estimate that Katrina-magnitude events have been twice as frequent in warm years compared with cold years (P < 0.02).

Temperature and precipitation extremes are examined in the Geoengineering Model Intercomparison Project experiment G1 , wherein an instantaneous quadrupling of CO 2 from its preindustrial control value is offset by a commensurate reduction in solar irradiance. Compared to the preindustrial climate, changes in climate extremes under G1 are generally much smaller than under 4 × CO 2 alone. However, it is also the case that extremes of temperature and precipitation in G1 differ significantly from those under preindustrial conditions. Probability density functions of standardized anomalies of monthly surface temperature and precipitation in G1 exhibit an extension of the high‐ tail over land, of the low‐ tail over ocean, and a shift of to drier conditions. Using daily model output, we analyzed the frequency of extreme events, such as the coldest night ( T N n ), warmest day ( T X x ), and maximum 5 day precipitation amount, and also duration indicators such as cold and warm spells and consecutive dry days. The strong heating at northern high latitudes simulated under 4 × CO 2 is much alleviated in G1 , but significant warming remains, particularly for T N n compared to T X x . Internal feedbacks lead to regional increases in absorbed solar radiation at the surface, increasing temperatures over Northern Hemisphere land in summer. Conversely, significant cooling occurs over the tropical oceans, increasing cold spell duration there. Globally, G1 is more effective in reducing changes in temperature extremes compared to precipitation extremes and for reducing changes in precipitation extremes versus means but somewhat less effective at reducing changes in temperature extremes compared to means.

Plants form belowground associations with mycorrhizal fungi in one of the most common symbioses on Earth. However, few large-scale generalizations exist for the structure and function of mycorrhizal symbioses, as the nature of this relationship varies from mutualistic to parasitic and is largely context-dependent. We announce the public release of MycoDB, a database of 4,010 studies (from 438 unique publications) to aid in multi-factor meta-analyses elucidating the ecological and evolutionary context in which mycorrhizal fungi alter plant productivity. Over 10 years with nearly 80 collaborators, we compiled data on the response of plant biomass to mycorrhizal fungal inoculation, including meta-analysis metrics and 24 additional explanatory variables that describe the biotic and abiotic context of each study. We also include phylogenetic trees for all plants and fungi in the database. To our knowledge, MycoDB is the largest ecological meta-analysis database. We aim to share these data to highlight significant gaps in mycorrhizal research and encourage synthesis to explore the ecological and evolutionary generalities that govern mycorrhizal functioning in ecosystems.

Abstract Aims To investigate the relationship between high diabetes‐related lower limb amputation incidence and foot care services in the South‐West region of England. Methods The introduction of 10 key elements of foot care service provision in one area of the South‐West resulted in stabilization of foot ulcer incidence and sustained reduction in amputation incidence from 2007. Services introduced included administrative support, standardized general practice foot screening, improved community podiatry staffing, hospital multidisciplinary foot clinics, effective care pathways, availability of an orthotist and audit. Peer reviews of the region's diabetes foot care services were undertaken to assess delivery of these service provisions and compare this with major amputation incidence in other regions with data provided by Yorkshire and Humber Public Health Observatory Hospital Episode Statistics. Recommendations were made to improve service provision. In 2015 changes in service provision and amputation incidence were reviewed. Results Initial reviews in 2013 showed that the 3‐year diabetes‐related major amputation incidence correlated inversely with adequate delivery of diabetes foot care services ( P =0.0024, adjusted R 2 =0.51). Repeat reviews in 2015 found that two or more foot care service improvements were reported by six diabetes foot care providers, with improvement in outcomes. The negative relationship between major amputation incidence and service provision remained strong both in the period 2012–2015 and in the year 2015 only ( P ≤0.0012, adjusted R 2 =0.56, and P = 0.0005, R 2 =0.62, respectively). Conclusions Major diabetes‐related lower limb amputation incidence is significantly inversely correlated with foot care services provision. Introduction of more effective service provision resulted in significant reductions in major amputation incidence within 2 years. Failure to improve unsatisfactory service provision resulted in continued high amputation incidence.

Abstract. The Geoengineering Model Intercomparison Project (GeoMIP) is a coordinating framework, started in 2010, that includes a series of standardized climate model experiments aimed at understanding the physical processes and projected impacts of solar geoengineering. Numerous experiments have been conducted, and numerous more have been proposed as “test-bed” experiments, spanning a variety of geoengineering techniques aimed at modifying the planetary radiation budget: stratospheric aerosol injection, marine cloud brightening, surface albedo modification, cirrus cloud thinning, and sunshade mirrors. To date, more than 100 studies have been published that used results from GeoMIP simulations. Here we provide a critical assessment of GeoMIP and its experiments. We discuss its successes and missed opportunities, for instance in terms of which experiments elicited more interest from the scientific community and which did not, and the potential reasons why that happened. We also discuss the knowledge that GeoMIP has contributed to the field of geoengineering research and climate science as a whole: what have we learned in terms of intermodel differences, robustness of the projected outcomes for specific geoengineering methods, and future areas of model development that would be necessary in the future? We also offer multiple examples of cases where GeoMIP experiments were fundamental for international assessments of climate change. Finally, we provide a series of recommendations, regarding both future experiments and more general activities, with the goal of continuously deepening our understanding of the effects of potential geoengineering approaches and reducing uncertainties in climate outcomes, important for assessing wider impacts on societies and ecosystems. In doing so, we refine the purpose of GeoMIP and outline a series of criteria whereby GeoMIP can best serve its participants, stakeholders, and the broader science community.

We studied the responses of temperate grasslands to climate change using a grassland ecosystem model which simulates seasonal dynamics of shoots, roots, soil water, mycorrhizal fungi, saprophytic microbes, soil fauna, inorganic nitrogen, plant residues and soil organic matter. Forty-year simulations were made for several climate change scenarios. The model was driven with observed weather and with combinations of elevated atmospheric CO2, elevated temperature, and either increased or decreased precipitation. Precipitation and CO2 level accounted for most of the variation among climate change treatments in the responses of soil, plants, animals and microbes. Elevated temperature extended the growing season but depressed photosynthesis in the summer, with little net effect on annual primary production. Doubling CO2 (1) caused persistent increases in primary production, in spite of greater nitrogen limitation, and (2) led to greater storage of carbon in plant residues and soil organic matter. The increased carbon storage was not great enough to keep pace with the present rate of increase in atmospheric CO2.

Agricultural practices affect the spatial patterns and dynamics of the decomposition of soil organic matter and the availability of plant-limiting nutrients. The biological processes underlying these patterns and dynamics are the trophic interactions among the organisms in the soil community food web. Food web models simulate nutrient flow rates close to observed rates and clarify the role of the various groups of organisms in the cycling of nutrients. Several large interdisciplinary programs are currently focusing on these interactions, with a view to developing and managing sustainable forms of agriculture.

The rate of sea level rise and its causes are topics of active debate. Here we use a delayed response statistical model to attribute the past 1000 years of sea level variability to various natural (volcanic and solar radiative) and anthropogenic (greenhouse gases and aerosols) forcings. We show that until 1800 the main drivers of sea level change are volcanic and solar radiative forcings. For the past 200 years sea level rise is mostly associated with anthropogenic factors. Only 4 ± 1.5 cm (25% of total sea level rise) during the 20th century is attributed to natural forcings, the remaining 14 ± 1.5 cm are due to a rapid increase in CO 2 and other greenhouse gases.

(1) Perturbations were performed on organisms in a below-ground trophic food web in a semi-arid grassland, using five separate biocide treatments to observe changes in trophic structures, interactions, and nutrient cycling. Changes in N mineralization and trophic interactions as predicted on the basis of simple predator-prey microcosm studies were observed following removal of particular groups. (2) Five biocides: streptomycin (bactericide), captan and PCNB (fungicides), carbofuran (insecticide-nematicide), and cygon (acaricide) were applied in situ to soil in cylinders containing predominantly blue grama grass. The response of microbes, fungal grazers, soil inorganic N and plants were followed monthly between April and October 1982. (3) Grazing of bacteria or fungi by predators resulted in one or more of the following occurrences: (i) increased soil inorganic N, decreased predator populations following reduction of prey or increased plant growth after reduction of nematodes; (ii) reduction of one group of decomposers, e.g. bacteria, allowed a second decomposer group, e.g., fungi, to increase in numbers; (iii) compensatory responses of microbial feeders, e.g. decreases in bacterial feeders (protozoa and bacterivorous nematodes) were followed by compensatory increases in fungal feeders, which increased following the increase in their fungal food supply. (4) Continuing changes in nitrogen cycling were not observed, presumably because the function of the reduced group was compensated by increased numbers of the second group performing a similar function. Nematode-VAM interactions must be considered in food web and nutrient flows, as the percentage of VAM colonization of plant roots increased markedly when nematode populations were decreased by nematicide treatment. Production of predator biomass was as important as microbial and plant production in determining nutrient flow in this system.

Theory and observation indicate that changes in the rate of primary production can alter the balance between the bottom‐up influences of plants and resources and the top‐down regulation of herbivores and predators on ecosystem structure and function. The Exploitation Ecosystem Hypothesis (EEH) posited that as aboveground net primary productivity (ANPP) increases, the additional biomass should support higher trophic levels. We developed an extension of EEH to include the impacts of increases in ANPP on belowground consumers in a similar manner as aboveground, but indirectly through changes in the allocation of photosynthate to roots. We tested our predictions for plants aboveground and for phytophagous nematodes and their predators belowground in two common arctic tundra plant communities subjected to 11 years of increased soil nutrient availability and/or exclusion of mammalian herbivores. The less productive dry heath (DH) community met the predictions of EEH aboveground, with the greatest ANPP and plant biomass in the fertilized plots protected from herbivory. A palatable grass increased in fertilized plots while dwarf evergreen shrubs and lichens declined. Belowground, phytophagous nematodes also responded as predicted, achieving greater biomass in the higher ANPP plots, whereas predator biomass tended to be lower in those same plots (although not significantly). In the higher productivity moist acidic tussock (MAT) community, aboveground responses were quite different. Herbivores stimulated ANPP and biomass in both ambient and enriched soil nutrient plots; maximum ANPP occurred in fertilized plots exposed to herbivory. Fertilized plots became dominated by dwarf birch (a deciduous shrub) and cloudberry (a perennial forb); under ambient conditions these two species coexist with sedges, evergreen dwarf shrubs, and Sphagnum mosses. Phytophagous nematodes did not respond significantly to changes in ANPP, although predator biomass was greatest in control plots. The contrasting results of these two arctic tundra plant communities suggest that the predictions of EEH may hold for very low ANPP communities, but that other factors, including competition and shifts in vegetation composition toward less palatable species, may confound predicted responses to changes in productivity in higher ANPP communities such as the MAT studied here.

Two isotopic ice core records from western Svalbard are calibrated to reconstruct more than 1000 years of past winter surface air temperature variations in Longyearbyen, Svalbard, and Vardø, northern Norway.Analysis of the derived reconstructions suggests that the climate evolution of the last millennium in these study areas comprises three major sub-periods.The cooling stage in Svalbard (ca.800Á1800) is characterized by a progressive winter cooling of approximately 0.9 8C century (1 (0.3 8C century (1 for Vardø) and a lack of distinct signs of abrupt climate transitions.This makes it difficult to associate the onset of the Little Ice Age in Svalbard with any particular time period.During the 1800s, which according to our results was the coldest century in Svalbard, the winter cooling associated with the Little Ice Age was on the order of 4 8C (1.3 8C for Vardø) compared to the 1900s.The rapid warming that commenced at the beginning of the 20th century was accompanied by a parallel decline in sea-ice extent in the study area.However, both the reconstructed winter temperatures as well as indirect indicators of summer temperatures suggest the Medieval period before the 1200s was at least as warm as at the end of the 1990s in Svalbard.

Recent advances in food‐web ecology highlight that most real food webs (1) represent an interplay between producer‐ and detritus‐based webs and (2) are governed by consumers which are rampant omnivores; feeding on varied prey across trophic levels and resource channels. A possible avenue to unify these advances comes from models demonstrating that predators feeding on distinctly different channels may stabilize food webs. Empirical studies suggest many consumers engage in such behavior by feeding on prey items from both living‐autotroph (green) and detritus‐based (brown) webs, what we term “multichannel feeding,” yet we know little about how common such feeding is across systems and trophic levels, or its effect on system stability. Considering 23 empirical webs, we find that multichannel feeding is equally common across terrestrial, freshwater, and marine systems, with &gt;50% of consumers classified as multichannel consumers. Multichannel feeding occurred most often at the first consumer level, indicating that most taxa at the herbivore/detritivore level are more aptly described as multichannel consumers, and that such feeding is not restricted to predators. We next developed a simple four‐compartment nutrient cycling model for consumers eating both autotrophs and detritus with separate parameter sets to represent aquatic vs. terrestrial ecosystems. Modeling results showed that, across terrestrial and aquatic ecosystems, multichannel feeding is stabilizing at low attack rates on autotrophs or when attack rates are asymmetric (moderate on autotrophs while low on detritus), but destabilizing at high attack rates on autotrophs, compared to herbivory‐ or detritivory‐only models. The set of conditions with stable webs with multichannel consumers is narrower, however, for aquatic systems, suggesting that multichannel feeding may generally be more stabilizing in terrestrial systems. Together, our results demonstrate that multichannel feeding is common across ecosystems and may be a stabilizing force in real webs that have consumers with low or asymmetric attack rates.

Abstract This book bridges the gap between the energetic and species approaches to studying food webs, addressing many important topics in ecology. Species, matter, and energy are common features of all ecological systems. Through the lens of complex adaptive systems thinking, the authors explore how the inextricable relationship between species, matter, and energy can explain how systems are structured, and how they persist in real and model systems. Food webs are viewed as open and dynamic systems. The central theme of the book is that the basis of ecosystem persistence and stability rests on the interplay between the rates of input of energy into the system from living and dead sources, and the patterns in utilization of energy which result from the trophic interactions among species within the system. To develop this theme, the authors integrate the latest work on community dynamics, ecosystem energetics, and stability. In so doing, they present a unified ecology that dispels the categorization of the field into the separate subdisciplines of population, community, and ecosystem ecology.

Abstract Desertification is among the most severe global environmental and the socio‐economic problems in the world. This paper is a first attempt to link scientific research to national policymaking on desertification in China. We aim to trace scientific research findings in the national policies and strategies of desertification prevention in China. One example is the large‐scale plantation programme in the dust source region threatening Beijing and Tianjin since 1998. It has been suggested that the recent increased forest cover due to plantations in North China has helped reduce dust storm emissions and contributed to mitigating dust storm weather in Beijing and Tianjin. Reforestation/afforestation policy remains in the Chinese national environmental strategies for the new national forestation programme (2011–2020). Overgrazing during recent decades has been blamed for land degradation and desertification in Northwest China by many scholars. Small field experiments prove that vegetation in desertified/degraded land could recover if isolated from human activities. Since 1998, natural recovery has become one powerful national force to prevent land desertification and recover natural vegetation. One example is selected at Cele County, Xinjiang Uygur Autonomous Region to showcase how vegetation could thrive at large scale in natural arid and semi‐arid climate if isolated from human intervention. The plantation project has pushed the stakeholders to better understand their negative impact on the environment, especially the overgrazing behaviour. After that, the household income and living level have also been significantly enhanced; however, it is not clear whether the project induced labour migration. Copyright © 2015 John Wiley &amp; Sons, Ltd.

Geoengineering has been proposed as a feasible way of mitigating anthropogenic climate change, especially increasing global temperatures in the 21st century. The two main geoengineering options are limiting incoming solar radiation, or modifying the carbon cycle. Here we examine the impact of five geoengineering approaches on sea level; SO(2) aerosol injection into the stratosphere, mirrors in space, afforestation, biochar, and bioenergy with carbon sequestration. Sea level responds mainly at centennial time scales to temperature change, and has been largely driven by anthropogenic forcing since 1850. Making use a model of sea-level rise as a function of time-varying climate forcing factors (solar radiation, volcanism, and greenhouse gas emissions) we find that sea-level rise by 2100 will likely be 30 cm higher than 2000 levels despite all but the most aggressive geoengineering under all except the most stringent greenhouse gas emissions scenarios. The least risky and most desirable way of limiting sea-level rise is bioenergy with carbon sequestration. However aerosol injection or a space mirror system reducing insolation at an accelerating rate of 1 W m(-2) per decade from now to 2100 could limit or reduce sea levels. Aerosol injection delivering a constant 4 W m(-2) reduction in radiative forcing (similar to a 1991 Pinatubo eruption every 18 months) could delay sea-level rise by 40-80 years. Aerosol injection appears to fail cost-benefit analysis unless it can be maintained continuously, and damage caused by the climate response to the aerosols is less than about 0.6% Global World Product.

Abstract We review the two main approaches to estimating sea level rise over the coming century: physically plausible models of reduced complexity that exploit statistical relationships between sea level and climate forcing, and more complex physics‐based models of the separate elements of the sea level budget. Previously, estimates of future sea level rise from semiempirical models were considerably larger than those from process‐based models. However, we show that the most recent estimates of sea level rise by 2100 using both methods have converged, but largely through increased contributions and uncertainties in process‐based model estimates of ice sheets mass loss. Hence, we focus in this paper on ice sheet flow as this has the largest potential to contribute to sea level rise. Progress has been made in ice dynamics, ice stream flow, grounding line migration, and integration of ice sheet models with high‐resolution climate models. Calving physics remains an important and difficult modeling issue. Mountain glaciers, numbering hundreds of thousands, must be modeled by extensive statistical extrapolation from a much smaller calibration data set. Rugged topography creates problems in process‐based mass balance simulations forced by regional climate models with resolutions 10–100 times larger than the glaciers. Semiempirical models balance increasing numbers of parameters with the choice of noise model for the observations to avoid overfitting the highly autocorrelated sea level data. All models face difficulty in separating out non‐climate‐driven sea level rise (e.g., groundwater extraction) and long‐term disequilibria in the present‐day cryosphere‐sea level system.

Abstract Analysis of surface and atmospheric energy budget responses to CO 2 and solar forcings can be used to reveal mechanisms of change in the hydrological cycle. We apply this energetic perspective to output from 11 fully coupled atmosphere‐ocean general circulation models simulating experiment G1 of the Geoengineering Model Intercomparison Project (GeoMIP), which achieves top‐of‐atmosphere energy balance between an abrupt quadrupling of CO 2 from preindustrial levels ( abrupt4xCO2 ) and uniform solar irradiance reduction. We divide the climate system response into a rapid adjustment , in which climate response is due to adjustment of the atmosphere and land surface on short time scales, and a feedback response , in which the climate response is predominantly due to feedback related to global mean temperature changes. Global mean temperature change is small in G1 , so the feedback response is also small. G1 shows a smaller magnitude of land sensible heat flux rapid adjustment than in abrupt4xCO2 and a larger magnitude of latent heat flux adjustment, indicating a greater reduction of evaporation and less land temperature increase than abrupt4xCO2 . The sum of surface flux changes in G1 is small, indicating little ocean heat uptake. Using an energetic perspective to assess precipitation changes, abrupt4xCO2 shows decreased mean evaporative moisture flux and increased moisture convergence, particularly over land. However, most changes in precipitation in G1 are in mean evaporative flux, suggesting that changes in mean circulation are small.

Our longitudinal study unpacks how an informal summer science and mathematics enrichment program influenced the educational pathways of four first-generation college-bound students. Through the lens of identity-in-practice and navigations, we explore their figured worlds of science, positioning and authoring of self in science as they applied to the program, as they participated in the program and later, in light of their college pathways. We explore the range of social and material supports the program made available to the four youth. We also show how they became consequential and for some facilitated navigations into college and STEM degrees while others experienced uncoordinated practices over time that pushed them out of science. Our study of local struggles at three pivotal moments in time attests to the agentive side of youth as they navigate in and out of science and engage in improvisational acts to get educated despite being tangled up in a matrix of oppression. At the same time, our study calls for systemic approaches that bring formal and informal science venues together in a more seamless manner. We call for a strength-based model that recognizes and leverages youths' figured worlds, positionings, and authored selves in science across context and over time in ways that they become consequential, empowering, and supportive of STEM pathways. We also call for more longitudinal studies committed to a theoretical grounding in identity-in-practice and navigations. © 2015 Wiley Periodicals, Inc. J Res Sci Teach 53: 768–801, 2016

The coupled regional climate model HIRHAM‐NAOSIM is used to investigate feedbacks between September sea ice anomalies in the Arctic and atmospheric conditions in autumn and the subsequent winter. A six‐member ensemble of simulations spanning the period 1949–2008 is analyzed. The results show that negative Arctic sea ice anomalies are associated with increased heat and moisture fluxes, decreased static stability, increased lower tropospheric moisture, and modified baroclinicity, synoptic activity, and atmospheric large‐scale circulation. The circulation changes in the following winter display meridionalized flow but are not fully characteristic of a negative Arctic Oscillation pattern, though they do support cold winter temperatures in northern Eurasia. Internally generated climate variability causes significant uncertainty in the simulated circulation changes due to sea ice‐atmosphere interactions. The simulated atmospheric feedback patterns depend strongly on the position and strength of the regional sea ice anomalies and on the analyzed time period. The strongest atmospheric feedbacks are related to sea ice anomalies in the Beaufort Sea. This work suggests that there are complex feedback mechanisms that support a statistical link between reduced September sea ice and Arctic winter circulation. However, the feedbacks depend on regional and decadal variations in the coupled atmosphere‐ocean‐sea ice system.

Ecologists have long recognized that ecosystems can exist and function in one state within predictable bounds for extended periods of time and then abruptly shift to an alternate state (1⇓⇓⇓–5). Desertification of grasslands, shrub expansion in the Arctic, the eutrophication of lakes, ocean acidification, the formation of marine dead zones, and the degradation of coral reefs represent real and potential ecological regime shifts marked by a tipping point or threshold in one or more external drivers or controlling variables within the system that when breached causes a major change in the system’s structure, function, or dynamics (6⇓⇓–9). Large or incremental alterations in climate, land use, biodiversity (invasive species or the overexploitation of species), and biogeochemical cycles represent external and internal drivers that when pushed too far cross thresholds that can could lead to regime shifts (Fig. 1). Seeing the tipping point after the fact and ascribing mechanisms to the change is one thing; predicting them using empirical data has been a challenge. The difficulty in predicting tipping points stems from the large number of species and interactions (high dimensionality) within ecological systems, the stochastic nature of the systems and their drivers, and the uncertainty and importance of initial conditions that the nonlinear nature of the systems introduce to outcomes. In PNAS, Jiang et al. (10) confront these issues using a dimension-reduction framework that uses empirical data from 59 complex multidimensional plant–pollinator mutualistic networks, some of which contain scores of species and interactions, to develop simpler 2D models for studying and predicting tipping points. Fig. 1. Tipping points and ecological regime shifts are difficult to predict. A and B represent hypothetical time series of the trajectories of the mean and variation about the mean of variables … [↵][1]1Email: John.Moore{at}colostate.edu. [1]: #xref-corresp-1-1

Geoengineering, which is the intentional large-scale manipulation of the environment, has been suggested as an effective means of mitigating global warming from anthropogenic greenhouse gas emissions. In this paper, we will review and assess technical and theoretical aspects of land-based, atmosphere-based, ocean-based and space-based geoengineering schemes as well as their potential impacts on global climate and ecosystem. Most of the proposed geoengineering schemes carried out on land or in the ocean are to use physical, chemical or biological approaches to remove atmospheric CO2. These schemes are able to only sequester an amount of atmospheric CO2 that is small compared with cumulative anthropogenic emissions. Most of geoengineering schemes carried out in the atmosphere or space are based on increasing planetary albedo. These schemes have relatively low costs and short lead times for technical implementation, and can act rapidly to reduce temperature anomalies caused by greenhouse gas emissions. The costs and benefits of geoengineering are likely to vary spatially over the planet with some countries and regions gaining considerably while others may be faced with a worse set of circumstances than would be the case without geoengineering. Since current research on geoengineering is limited and various international treaties may limit some geoengineering experiments in the real world, the Geoengineering Model Intercomparison Project (GeoMIP) provides a framework of coordinated experiments for all earth system modeling groups to test geoengineering schemes. However, these experiments used on a global scale have difficulty with accurate resolution of regional and local impacts, so future research on geoengineering is expect to be done by combining earth system models with regional climate models.

Nitrogen deposition from anthropogenic sources is a global problem that reaches even the most remote ecosystems. Responses belowground vary by ecosystem, and have feedbacks to geochemical processes, including carbon storage. A long-term nitrogen addition study in a subalpine forest has shown carbon loss over time, atypical for a forest ecosystem. Loss of microbial biomass is likely linked to lower soil carbon, but the mechanism behind this is still unknown. One possible explanation is through increased turnover due to grazing by soil fauna. Because nematodes occupy many trophic levels and are sensitive to trophic and environmental changes, assessing their communities helps reveal belowground responses. In this study, we tested the hypothesis that long-term nitrogen fertilization affects nematode community structure and maturity beneath coniferous forests in the Rocky Mountains, indicating a faster cycling, bacterial-driven system. We identified and enumerated nematodes by trophic group and family from experimental plots. Total nematode abundance was 40–96% greater in fertilized plots compared to the control, but richness, diversity, and ecological maturity were lower. The differences in abundance were driven by opportunistic bacterivores (e.g., Rhabditidae) and plant parasites (e.g., Tylenchidae), which made up 23 and 13% of the community in fertilized compared to 7 and 5% in control plots, respectively. Nematode maturity indices showed that the nematode food web was enriched (indicating high nutrient/resource status) and structured (all trophic levels present, including long-lived predators) in both treatments, but significantly more enriched in the fertilized treatment. Nonmetric multidimensional scaling of the relative abundance of nematode families demonstrated that nematode community composition differed between treatments, driven largely by opportunistic bacterivores (e.g., Rhabditidae) in the fertilized plots. The mechanism of the aboveground–belowground link between nitrogen deposition and nematode community composition is likely through increased microbial turnover, and sustained high-quality food for microbial grazing nematodes.

Abstract Geoengineering via solar radiation management could affect agricultural productivity due to changes in temperature, precipitation, and solar radiation. To study rice and maize production changes in China, we used results from 10 climate models participating in the Geoengineering Model Intercomparison Project (GeoMIP) G2 scenario to force the Decision Support System for Agrotechnology Transfer (DSSAT) crop model. G2 prescribes an insolation reduction to balance a 1% a −1 increase in CO 2 concentration (1pctCO2) for 50 years. We first evaluated the DSSAT model using 30 years (1978–2007) of daily observed weather records and agriculture practices for 25 major agriculture provinces in China and compared the results to observations of yield. We then created three sets of climate forcing for 42 locations in China for DSSAT from each climate model experiment: (1) 1pctCO2, (2) G2, and (3) G2 with constant CO 2 concentration (409 ppm) and compared the resulting agricultural responses. In the DSSAT simulations: (1) Without changing management practices, the combined effect of simulated climate changes due to geoengineering and CO 2 fertilization during the last 15 years of solar reduction would change rice production in China by −3.0 ± 4.0 megaton (Mt) (2.4 ± 4.0%) as compared with 1pctCO2 and increase Chinese maize production by 18.1 ± 6.0 Mt (13.9 ± 5.9%). (2) The termination of geoengineering shows negligible impacts on rice production but a 19.6 Mt (11.9%) reduction of maize production as compared to the last 15 years of geoengineering. (3) The CO 2 fertilization effect compensates for the deleterious impacts of changes in temperature, precipitation, and solar radiation due to geoengineering on rice production, increasing rice production by 8.6 Mt. The elevated CO 2 concentration enhances maize production in G2, contributing 7.7 Mt (42.4%) to the total increase. Using the DSSAT crop model, virtually all of the climate models agree on the sign of the responses, even though the spread across models is large. This suggests that solar radiation management would have little impact on rice production in China but could increase maize production.

Species extinctions are accelerating globally, yet the mechanisms that maintain local biodiversity remain poorly understood. The extinction of species that feed on or are fed on by many others (i.e. 'hubs') has traditionally been thought to cause the greatest threat of further biodiversity loss. Very little attention has been paid to the strength of those feeding links (i.e. link weight) and the prevalence of indirect interactions. Here, we used a dynamical model based on empirical energy budget data to assess changes in ecosystem stability after simulating the loss of species according to various extinction scenarios. Link weight and/or indirect effects had stronger effects on food-web stability than the simple removal of 'hubs', demonstrating that both quantitative fluxes and species dissipating their effects across many links should be of great concern in biodiversity conservation, and the potential for 'hubs' to act as keystone species may have been exaggerated to date.

Earth's FutureVolume 6, Issue 2 p. 230-251 Research ArticleOpen Access Regional Climate Impacts of Stabilizing Global Warming at 1.5 K Using Solar Geoengineering Anthony C. Jones, Corresponding Author Anthony C. Jones anthony.jones@metoffice.gov.uk orcid.org/0000-0002-3894-2867 College of Engineering, Maths and Physical Sciences (CEMPS), University of Exeter, Exeter, UK Correspondence to: Anthony C. Jones, anthony.jones@metoffice.gov.ukSearch for more papers by this authorMatthew K. Hawcroft, Matthew K. Hawcroft College of Engineering, Maths and Physical Sciences (CEMPS), University of Exeter, Exeter, UKSearch for more papers by this authorJames M. Haywood, James M. Haywood orcid.org/0000-0002-2143-6634 College of Engineering, Maths and Physical Sciences (CEMPS), University of Exeter, Exeter, UK Earth System and Mitigation Science, Met Office, Exeter, UKSearch for more papers by this authorAndy Jones, Andy Jones orcid.org/0000-0003-1814-7601 Earth System and Mitigation Science, Met Office, Exeter, UKSearch for more papers by this authorXiaoran Guo, Xiaoran Guo College of Global Change and Earth System Science, Beijing Normal University, Beijing, ChinaSearch for more papers by this authorJohn C. Moore, John C. Moore orcid.org/0000-0001-8271-5787 College of Global Change and Earth System Science, Beijing Normal University, Beijing, China Arctic Centre, University of Lapland, Rovaniemi, FinlandSearch for more papers by this author Anthony C. Jones, Corresponding Author Anthony C. Jones anthony.jones@metoffice.gov.uk orcid.org/0000-0002-3894-2867 College of Engineering, Maths and Physical Sciences (CEMPS), University of Exeter, Exeter, UK Correspondence to: Anthony C. Jones, anthony.jones@metoffice.gov.ukSearch for more papers by this authorMatthew K. Hawcroft, Matthew K. Hawcroft College of Engineering, Maths and Physical Sciences (CEMPS), University of Exeter, Exeter, UKSearch for more papers by this authorJames M. Haywood, James M. Haywood orcid.org/0000-0002-2143-6634 College of Engineering, Maths and Physical Sciences (CEMPS), University of Exeter, Exeter, UK Earth System and Mitigation Science, Met Office, Exeter, UKSearch for more papers by this authorAndy Jones, Andy Jones orcid.org/0000-0003-1814-7601 Earth System and Mitigation Science, Met Office, Exeter, UKSearch for more papers by this authorXiaoran Guo, Xiaoran Guo College of Global Change and Earth System Science, Beijing Normal University, Beijing, ChinaSearch for more papers by this authorJohn C. Moore, John C. Moore orcid.org/0000-0001-8271-5787 College of Global Change and Earth System Science, Beijing Normal University, Beijing, China Arctic Centre, University of Lapland, Rovaniemi, FinlandSearch for more papers by this author First published: 08 February 2018 https://doi.org/10.1002/2017EF000720Citations: 34AboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Abstract The 2015 Paris Agreement aims to limit global warming to well below 2 K above preindustrial levels, and to pursue efforts to limit global warming to 1.5 K, in order to avert dangerous climate change. However, current greenhouse gas emissions targets are more compatible with scenarios exhibiting end-of-century global warming of 2.6–3.1 K, in clear contradiction to the 1.5 K target. In this study, we use a global climate model to investigate the climatic impacts of using solar geoengineering by stratospheric aerosol injection to stabilize global-mean temperature at 1.5 K for the duration of the 21st century against three scenarios spanning the range of plausible greenhouse gas mitigation pathways (RCP2.6, RCP4.5, and RCP8.5). In addition to stabilizing global mean temperature and offsetting both Arctic sea-ice loss and thermosteric sea-level rise, we find that solar geoengineering could effectively counteract enhancements to the frequency of extreme storms in the North Atlantic and heatwaves in Europe, but would be less effective at counteracting hydrological changes in the Amazon basin and North Atlantic storm track displacement. In summary, solar geoengineering may reduce global mean impacts but is an imperfect solution at the regional level, where the effects of climate change are experienced. Our results should galvanize research into the regionality of climate responses to solar geoengineering. Key Points We perform simulations in which solar geoengineering is used to stabilize global warming at 1.5 K above preindustrial levels Enhanced storm surge activity and heatwave increases under global warming are effectively counteracted by solar geoengineering Solar geoengineering does little to counteract Amazonian hydrological changes and North Atlantic storm track displacement 1 Introduction In light of the 2015 Paris Agreement that compels participating nations to mitigate greenhouse gas (GHG) emissions at a sufficient rate to avert global warming of 2 K above preindustrial levels (and with the optimal target of avoiding 1.5 K) it has fallen to the climate science community to elucidate plausible mitigation pathways which may limit global warming to 1.5 K (UNFCCC, 2015). Global warming has widely been adopted as a target for GHG mitigation efforts due to its intrinsic relationship with both accumulated carbon dioxide (CO2) emissions and regional climate changes. The extent to which global-mean temperature targets such as 2 or 1.5 K represent associated climate impacts at a regional level remains uncertain (Knutti et al., 2016). There remains considerable uncertainty surrounding the feasibility of achieving the 1.5 K target using conventional mitigation alone, given historical and present-day GHG emission trends. For example, 56% of coupled global climate models (GCMs) participating in CMIP5 predict that global mean temperature levels will be more than 1.5 K above preindustrial levels by the end of the 21st century under even the most stringent RCP2.6 mitigation scenario (e.g., Table 12.3 in Collins et al., 2013). Rogelj et al. (2016) found that current mitigation strategies arising from the Paris agreement (Nationally Determined Contributions [NDCs]) are more consistent with scenarios in which end-of-century global warming reaches 2.6–3.1 K rather than 1.5 K. On the other hand Millar et al. (2017) show that current GCMs overestimate recent historical global temperature change and underestimate the cumulative amount of CO2 emitted during the industrial period. This latter result suggests that, while stringent cuts in CO2 emission will certainly be required, we are not yet at the point where the 1.5 K target is unachievable through conventional mitigation alone. However, the United States—currently the world's second largest GHG emitter behind China—looks set to withdraw from the Paris agreement (Gies, 2017); an act which signifies the difficulty nations will have in cooperatively adhering to effective mitigation pathways in the long-term future. Various carbon dioxide removal (CDR) methods have been proposed to facilitate conventional mitigation in achieving temperature targets (Shepherd, 2009), and CDR is often implicitly utilized in simulations of idealized future scenarios with GCMs (Rogelj et al., 2015). However, it is possible that the potential efficacy of these largely untested CDR approaches has been over-estimated (e.g., Boysen et al., 2017) meaning that climate scenarios dependent on negative CO2 emissions (e.g., RCP2.6; van Vuuren et al., 2011) might be overly optimistic and unattainable. This is particularly poignant considering the lack of political traction for CDR investment thus far, for instance, the near ubiquitous omission of CDR in the NDCs (Peters & Geden, 2017). Another important caveat when considering the feasibility of limiting global warming to 1.5 K concerns the fluxes of CO2 and methane (CH4) between the atmosphere, the oceans, and the land, with projections largely unconstrained by the CMIP5 GCMs. Therefore, natural GHG fluxes to the atmosphere might augment anthropogenic GHG emissions should the ocean or land become a net carbon source in the future (Friedlingstein et al., 2014). This only adds to the uncertainty of whether effective mitigation and CDR could achieve the Paris temperature targets. In summary, the 1.5 K target appears difficult to achieve by conventional mitigation or using current CDR technology alone without incurring an overshoot, that is, a scenario in which global warming exceeds 1.5 K and is “brought back” to a desired temperature by CDR and mitigation (Scenario 3 in Figure 1). Alternatively solar geoengineering, else known as solar radiation management (SRM), has been proposed as a method for cooling the planet and could be used to stabilize Earth's temperature at 1.5 K instead of incurring a temperature overshoot (Scenario 4 in Figure 1) (Chen & Xin, 2017). SRM refers to a range of climate interventions that aim to increase the reflectivity of the atmosphere or surface to sunlight, hence reducing the absorption of solar energy within the climate system (Shepherd, 2009). Specific SRM strategies include stratospheric aerosol injection (SAI) which mimics large volcanic eruptions (Budyko, 1977; Crutzen, 2006), marine cloud brightening which mimics ship tracks and continuously degassing volcanoes (Latham, 1990; Malavelle et al., 2017), and cirrus cloud thinning (CCT) which aims to enhance outgoing terrestrial radiation by reducing high-altitude cirrus coverage (Mitchell & Finnegan, 2009). Note that CCT is technically an example of Longwave Radiation Management rather than SRM as cirrus clouds exert a stronger positive radiative effect from absorbing longwave terrestrial radiation when compared to their negative radiative effect from reflecting shortwave solar radiation. Other SRM strategies such as space mirrors, land albedo modification, and ocean-surface brightening have also been suggested but have received limited attention due to projected costs or projections of large regional climate changes (e.g., Crook et al., 2015; Gabriel et al., 2017; NRC, 2015). A Royal Society report identified SAI as the most promising SRM proposal (Shepherd, 2009); hence we shall solely investigate SAI in this study. Figure 1Open in figure viewerPowerPoint Schematic of 21st century global warming trends under various scenarios (credit to David MacKay). Note: the similarity between this schematic and Figure 2 of Tilmes et al. (2016). Studies with GCMs indicate that SRM could effectively counteract global warming (e.g., Jones et al., 2016a; Tilmes et al., 2016) but would not be able to simultaneously offset temperature and precipitation changes in all regions (Kravitz et al., 2014; Ricke et al., 2010). This begs the question of whether global-mean temperature targets such as 2 or 1.5 K fully represent regional climate impacts. Also, what would be the trade-offs of using SRM in place of mitigation and CDR to achieve certain temperature targets? In order to answer such questions, it is important to identify climate changes that may result from global warming and then address on a case-by-case basis whether SRM would counteract or amplify these climate changes. Additionally, it is important to identify any additional risks that SRM may introduce. Although the impacts of climate change are felt on the regional scale, certain climate changes such as sea-ice loss, sea-level rise, and changes to the hydrological cycle have global impacts (Collins et al., 2013). Arctic sea ice has retreated over the last four decades due to anthropogenic global warming (Kinnard et al., 2011) and will continue to diminish as the Earth warms, with GCM results suggesting ice-free summers in the Arctic by the end of the century (Mahlstein & Knutti, 2012). The global-mean sea level (GMSL) rose by approximately 1.2 mm/year in the 20th century due to global warming, predominantly via thermosteric effects due to the uptake of heat by the oceans (Hay et al., 2015). A GMSL rise of between 0.26 and 0.55 m for a mitigation-intensive scenario (RCP2.6) and 0.45–0.82 m for a business-as-usual scenario (RCP8.5) is predicted by the end of the 21st century (Church et al., 2013), with additional committed GMSL rise in the longer term due to Antarctic ice loss (Golledge et al., 2015). Sea-level rise will primarily impact coastal populations and small island states, and will increase the risk of flooding and storm surges (Neumann et al., 2015). The hydrological impacts of global warming will vary with region, although precipitation is generally expected to increase which can be explained in part by the Clausius–Clapeyron relationship (i.e., that warmer air holds more water vapor; Collins et al., 2013). For land regions, it is generally predicted that wet regions will get wetter and dry regions will get drier, except for the interesting case of the Amazon basin. Models predict that the Amazonian dry season will be strengthened by global warming, which will concomitantly increase the risk of forest fires and may possibly lead to the degradation or dieback of the tropical rainforest (Boisier et al., 2015; Malhi et al., 2008). Global warming is also predicted to increase the risk of extreme events such as heatwaves and hurricanes (Emanuel, 2013; Fischer & Knutti, 2015). A heatwave in Europe in the boreal summer of 2003 resulted in 70,000 deaths across 16 countries (Robine et al., 2008), economic losses of $ 10 US billion, extensive forest fires in Greece, Italy, France, Spain, and notably Portugal (covering ∼5% of Portuguese territory), and widespread crop and livestock loss (García-Herrera et al., 2010; Schär & Jendritzky, 2004). Contemporaneous forest fires contributed to increased surface ozone emissions resulting in enhanced air pollution across the continent (García-Herrera et al., 2010). Low precipitation rates in spring 2003 resulted in anomalously low soil moisture content across Europe, reducing summertime continental cloud coverage and exerting a positive feedback on the heatwave, concomitantly reducing gross primary productivity (GPP) (Ciais et al., 2005). The 2003 heatwave was not an anomaly—the last decade has seen multiple heatwaves in Europe, including in 2010 and 2015, with the latter leading to the driest and second hottest summer in recent decades (Dong et al., 2016). Heatwaves are subcontinental in extent (a few thousand kilometers), which may limit impacts to certain countries. A heatwave in West Russia in summer 2010 resulted in 55,000 additional deaths, reduced annual crop production by 25% and caused economic losses of $ 15 US billion (Barriopedro et al., 2011). Observations indicate that temperature extremes have increased over land (Brown et al., 2008) and that historical anthropogenic GHG emissions have increased the risk of European heatwaves (Christidis et al., 2011, 2015; Fischer & Knutti, 2015; Stott et al., 2004). GCM simulations indicate that European heatwaves will become longer, more frequent, and more intense in the 21st century under continued global warming (Lau & Nath, 2014; Meehl & Tebaldi, 2004; Russo et al., 2015; Schoetter et al., 2015). Heatwaves are also projected to increase in other regions such as the United States and Australia (Cowan et al., 2014; Lau & Nath, 2012; Meehl & Tebaldi, 2004). Moving to tropical storms, the 2017 North Atlantic hurricane season has been one of the deadliest and costliest in recent memory with estimated economic damages exceeding $300 US billion, which can be compared to the 2005 season where Hurricane Katrina-related damages exceeded $211 US billion (Johnson, 2017). In general, the greatest Hurricane-related risk is from wind-driven storm surges, which primarily threaten low-lying coastal populations including many cities along the south-western coast of the United States (Knutson et al., 2010; Rappaport, 2014). The threat to coastal populations and industry from storm surges is amplified by increases to population density and by sea-level rise. The frequency of intense hurricanes in the North Atlantic basin is predicted to increase as a result of global warming, but there is no consensus over the response of overall storm activity to global warming (Emanuel, 2013; Walsh et al., 2016). Coupled with projected sea-level rise and coastal population growth, an increase in the number of intense storms would magnify the impacts of storm-surge events. It is important to question whether the use of SRM to stabilize global warming at 1.5 K (Scenario 4 in Figure 1) would counteract climate changes compared to baseline scenarios in which the 1.5 K target is exceeded (Scenarios 1–3 in Figure 1). The climate impacts of SRM have been widely researched through the use of GCMs and through validation with postvolcanic eruption observations. These results have shown that a globally uniform SRM deployment would generally be effective at counteracting regional surface temperature and precipitation changes (Jones et al., 2016a; Kravitz et al., 2014), and may enhance net primary productivity by reducing heat stress and enhancing diffuse solar radiation at the surface (Xia et al., 2016). SRM may also be effective at counteracting sea-ice loss and thermosteric sea-level rise (Berdahl et al., 2014; Irvine et al., 2012; Jones et al., 2016a), and offsetting increases to temperature extremes (Curry et al., 2014). However, SRM would also alter stratospheric ozone concentrations by changing stratospheric chemistry and dynamics, which could potentially enhance levels of harmful ultraviolet radiation at the surface (Pitari et al., 2014). Additionally, SRM would not counteract ocean acidification due to elevated CO2 concentrations, and any termination or rapid slowdown of SRM deployment may cause climate change at an unprecedented rate (Jones et al., 2013). Although much research has been devoted to SRM in the last decade, little has been invested in the impacts on specific climate phenomena such as heatwaves or storms (although a few recent studies have begun to explore storm changes [Moore et al., 2015; Jones et al., 2017]). Additionally, no existing modeling study has specifically considered the implications of using SRM to stabilize global-mean temperature at 1.5 K, which is the aim of this study. We investigate the climatic impacts of SRM in the context of the 1.5 K target by performing simulations with the Hadley Centre Global Environment Model version 2 (HadGEM2-ES). We use three baseline GHG concentrations scenarios from the Representative Concentrations Pathway (RCP) suite: the mitigation and CDR-intensive RCP2.6 (van Vuuren et al., 2011), the middle-of-the-road RCP4.5 (Thomson et al., 2011), and the carbon-intensive RCP8.5 (Riahi et al., 2011). While there are an infinite number of possible future scenarios, in essence, these baseline scenarios represent the scenarios “Mitigation and CDR,” “Mitigation,” and “No Mitigation” in Figure 1, respectively. Note, however, that RCP4.5 implicitly assumes a considerable degree of CDR by the end of the century, and is thus not truly representative of standalone mitigation (Thomson et al., 2011). In our geoengineering scenarios, we assess the repercussions of using SRM to stabilize global warming at 1.5 K while society swiftly transitions onto a mitigation and CDR-intensive pathway (Scenario 4 in Figure 1). We also explore scenarios in which SRM is used in place of mitigation and/or CDR (i.e., Scenarios 1 and 2 in Figure 1 plus SRM, see Section 2). We represent SRM using SAI, that is, by injecting gaseous sulfur dioxide (SO2) into the model stratosphere, following which the SO2 oxidizes to form a cloud of light-scattering sulfate (SO4) aerosol (Jones et al., 2010; Kravitz et al., 2011). Our analysis first concentrates on the evolution of globally averaged climate variables such as temperature and precipitation (Section 3.1). We then compare regional climate changes between a recent historical period (1985–2005) and the RCP/SAI simulations evaluated at the end of the 21st century (2070–2099) (Section 3.2). Finally, in Sections 3.3–3.5 we investigate changes to various impactful climate change phenomena—Amazonian drying trends, European heatwaves and North Atlantic extreme hurricane frequency—under SAI and global warming. We discuss the implications of our results in Section 4. 2 Model and Methods HadGEM2-ES is a fully coupled atmosphere–ocean GCM, with an atmospheric horizontal resolution of N96 (1.875° × 1.25°) and 38 vertical levels extending to approximately 40 km altitude, and an oceanic horizontal resolution of 1° (extending to 1/3° at the equator) and 40 vertical levels (Collins et al., 2011; Jones et al., 2011; Martin et al., 2011). The “ES” in HadGEM2-ES refers to the “Earth System” component of the model, that is, the inclusion of a terrestrial/oceanic carbon cycle and the TRIFFID dynamical vegetation model. HadGEM2-ES includes the UKCA tropospheric chemistry scheme with 25 tracers representing 41 chemical species (O'Connor et al., 2014), and the CLASSIC single-moment aerosol scheme with six externally mixed aerosol species (Bellouin et al., 2007, 2011). The CLASSIC sulfur scheme represents the oxidation of SO2 and dimethylsulfide (DMS) to form SO4 aerosol in aqueous and gas phase reactions. SO4 is then partitioned into Aitken and accumulation size modes (represented by fixed unimodal lognormal size distributions) and a “dissolved” or “in-cloud” mode. CLASSIC represents the aerosol-related processes of coagulation and mode-merging (Aitken -> accumulation), diffusion (Aitken ->dissolved), nucleation and evaporation (accumulation <−-> dissolved), sedimentation, hygroscopic growth, and dry/wet deposition in the troposphere (Bellouin et al., 2007). SO4 is also able to act as cloud condensation nuclei (CCN), permitting evaluation of aerosol indirect radiative effects (Bellouin et al., 2007). The SO4 aerosol is fully coupled with the shortwave (SW) and longwave (LW) radiation, which is partitioned into six and nine wavebands, respectively (Bellouin et al., 2007). The baseline simulations follow CMIP5 protocol (Taylor et al., 2012) and are outlined comprehensively in Jones et al. (2011). Briefly, time-dependent emissions of aerosols (excepting sea-salt and mineral dust), their precursor gases (excepting oceanic DMS), and atmospheric GHG concentrations follow CMIP5 specifications exclusive for each scenario with historical values derived from observations (Meinshausen et al., 2011; Taylor et al., 2012). Tropospheric concentrations of ozone (O3), hydroxyl (OH), hydroperoxyl (HO2), and hydrogen peroxide (H2O2) (which are utilized by CLASSIC as atmospheric oxidants) are directly output from UKCA at each time-step, while stratospheric concentrations of these species are prescribed as monthly mean fields. The suite of simulations comprise a 240-year constant “pre-industrial (1860) conditions” simulation (piControl); a four-member historical (HIST, 1860–2005) ensemble; four-member RCP2.6/ RCP4.5/ RCP8.5 (2005–2099) ensembles following CMIP5 specifications; and four-member RCP2.6/ RCP4.5/ RCP8.5 plus SAI (denoted GEO2.6/ GEO4.5/ GEO8.5) ensembles. We instigate SAI in model year 2020 and inject SO2 at a sufficient rate as to stabilize annual and global-mean warming at 1.5 K above the piControl mean. In the SAI simulations, SO2 is injected evenly between 16 and 25 km altitude (six vertical grid cells). As in other SAI studies with HadGEM2-ES (e.g., Haywood et al., 2013; Jones et al., 2010, 2017), we compensate for the lack of an adequately resolved quasi-biennial oscillation (QBO) owing to the limited height of the top of the model by injecting uniformly over the globe rather than injecting at a single point (e.g., Jones et al., 2016b). Our precise method for determining sufficient stratospheric SO2 injection rates as to attain 1.5 K is described in Text S1 in the Supporting Information S1. 3 Results 3.1 Annual and Global-Mean Climate Variables Figure 2 shows various annual and global-mean climate anomalies averaged over each four-member ensemble for each scenario. From Figure 2a, we clearly manage to stabilize global-mean temperature at approximately 1.5 K above piControl levels throughout the 2020–2099 period in the GEO simulations. The GEO2.6, GEO4.5, and GEO8.5 scenarios all succeed in maintaining global-warming since preindustrial times below 1.5 K, while the corresponding RCP2.6, RCP4.5, and RCP8.5 scenarios exceed the 1.5 K target (Table 1). The 2070–2099 RCP anomalies relative to 1986–2005 (Table 1) of 1.46, 2.42, and 4.34 K in RCP2.6, RCP4.5, and RCP8.5, respectively, can be compared to their respective values from the CMIP5 ensemble: +1 [0.3, 1.7] K in RCP2.6, +1.8 [1, 2.5] K in RCP4.5 and 3.4 [2.2, 4.7] K in RCP8.5, where square brackets denote 90% uncertainty ranges. The HadGEM2-ES estimates are therefore at the upper end of the CMIP5 bracket, suggesting a comparatively high transient model sensitivity, as also found by Stott et al. (2013). Figure 2Open in figure viewerPowerPoint Time series of annual- and global-mean climate variables. (a) near-surface (1.5 m) air temperature anomaly relative to piControl, (b) geoengineering SO2 emissions, (c) 5-year smoothed precipitation anomaly relative to HIST (1986–2005), (d) 5-year smoothed net downwelling radiation at the top-of-the-atmosphere (TOA), (e) Northern hemisphere (NH) sea ice anomaly relative to HIST, (f) thermosteric sea-level anomaly relative to HIST. Vertical dashed lines indicate the initiation of SAI, and the horizontal line in (a) delineates the 1.5 K target. Table 1. Global-Mean Temperature Anomalies for: (Column 2) 2020–2099 Relative to the Preindustrial Control Simulation and (Column 3) 2070–2099 Relative to HIST (1986–2005) Scenario 2020–2099 global warming relative to piControl 2070–2099 global warming relative to 1986–2005 RCP2.6 1.77 [1.74, 1.80] 1.46 [1.40, 1.53] RCP4.5 2.27 [2.24, 2.29] 2.42 [2.26, 2.56] RCP8.5 3.29 [3.27, 3.35] 4.34 [4.26, 4.43] GEO2.6 1.42 [1.37, 1.46] 0.99 [0.87, 1.05] GEO4.5 1.37 [1.33, 1.40] 1.01 [0.91, 1.10] GEO8.5 1.49 [1.44, 1.52] 1.08 [0.96, 1.21] Values in brackets denote the ensemble ranges. The interannual standard deviation of the detrended temperature time series is approximately ±0.1 K in each of the simulations In GEO2.6, the SO2 injection rate peaks at 3.95 Tg[SO2]/year, then plateaus at 3.5 Tg[SO2]/year. until 2080, then decreases to 1.7 Tg[SO2]/year in 2100 as Earth cools in RCP2.6 due to the implicit upscaling of CDR later in the century (Figure 2b). In GEO4.5, the injection rate increases monotonically to attain a peak value of 10.9 Tg[SO2]/year in 2080 following which it plateaus as global warming in RCP4.5 stabilizes at slightly above 3 K (Figure 2b). In the GEO8.5 scenario, SO2 emissions increase quasi-linearly for the duration of the simulations reaching a peak of 29.7 Tg[SO2]/year in 2100. The injection rates given above must be treated with caution due to the simple aerosol microphysics scheme in HadGEM2-ES which does not account for continuous aerosol growth (Text S2 in Supporting Information S1) (Kleinschmitt et al., 2017; Niemeier & Timmreck, 2015). Therefore, the SO2 injection rates required to stabilize global warming at 1.5 K may be underestimated in these simulations, as larger-sized aerosol will have a shorter stratospheric lifetime and a greater influence on terrestrial radiation making it less effective at cooling the Earth and hence will require more regular replenishing. The Northern Hemisphere (NH) sea-ice extent anomaly is effectively stabilized at −4 × 106 km2 relative to 1985–2005 levels in all of the SAI simulations (Figure 2e), coincident with the global-mean temperature stabilization (Figure 2a). However, due to committed warming and a consistently positive top-of-the-atmosphere (TOA) net radiation imbalance (Figure 2d), the global-mean thermosteric sea-level increases monotonically in all of the SAI simulations (Figure 2f), albeit at a slower rate than in the corresponding RCP simulations. Jones et al. (2016a) found that deploying SAI at a sufficient rate as to equilibrate TOA radiative fluxes could effectively stabilize global-mean thermosteric sea level during the 21st century, but this SAI strategy may conflict with specific temperature objectives, such as the 1.5 K target (Irvine et al., 2012). GEO8.5 is also unable to simultaneously stabilize temperature and precipitation (Figure 2c), which is due to the hydrological cycle being more sensitive to changes in SW radiation than that in LW radiation (Bala et al., 2008), and is a robust result of SAI and enhanced stratospheric aerosol burdens following volcanic eruptions (e.g., Tilmes et al., 2013; Trenberth & Dai, 2007). The precipitation trends in GEO2.6 and GEO4.5 are +0.001 and −0.002 mm/day/decade, respectively, which can be compared to −0.016 mm/d/decade in GEO85, suggesting that the nonperfect compensation of global-mean precipitation when temperatures are held fixed by SRM (e.g., Bala et al., 2008) are most evident when the SRM forcing is strong. 3.2 Regional Climate Changes in 2070–2099 Relative to 1986–2005 Despite the prescribed SO2 injection rates being equal in the NH and southern hemisphere (SH) in the SAI simulations, the resultant 550 nm sulfate aerosol optical depth (AOD) anomaly is consistently greater in the NH than the SH, albeit by 1–3% when averaged over the hemisphere (Table S1 in Supporting Information S1). In particular, the aerosol is

We analyze the sea level rise along the Bohai Sea, the Yellow Sea, the East China Sea, and the South China Sea (the "China Seas") coastline using 25 tide gauge records beginning with Macau in 1925, but with most starting during the 1950s and 60s. The main problem in estimating sea level rise for the period is the lack of vertical land movement (VLM) data for the tide gauge stations. We estimated VLM using satellite altimetry covering the 18 stations with records spanning 1993–2016. The results show that many tide gauge stations, typically in cities, have undergone significant subsidence due to groundwater extraction. After removing the VLM from tide gauge records, the 1993–2016 sea level rise rate is 3.2 ± 1.1 mm/yr, and 2.9 ± 0.8 mm/yr over the longer 1980–2016 period. We estimate the steric sea level contribution to be up to 0.9 ± 0.3 mm/yr, and contributions from ice mass loss from glaciers and ice sheets of up to 1.1 ± 0.1 mm/yr over the last 60 years. Contributions from VLM range between −4.5 ± 1.0 mm/yr and 1.4 ± 1.3 mm/yr across the stations. Projections of coastal sea level probability distributions under future climate scenarios show that the steric factor is the main contributor under both the RCP 4.5 and High-end RCP 8.5 scenarios except in the upper tails under High-end RCP 8.5 when the Antarctic ice sheet makes the greatest contribution. By 2100 we expect median coastal sea level rises at the stations of 48–61 cm under RCP 4.5, and 84–99 cm under High-end RCP 8.5 scenario.

Abstract Snow depth on the interior of Tibetan Plateau (TP) in state-of-the-art reanalysis products is almost an order of magnitude higher than observed. This huge bias stems primarily from excessive snowfall, but inappropriate process representation of shallow snow also causes excessive snow depth and snow cover. This study investigated the issue with respect to the parameterization of fresh snow albedo. The characteristics of TP snowfall were investigated using ground truth data. Snow in the interior of the TP is usually only some centimeters in depth. The albedo of fresh snow depends on snow depth, and is frequently less than 0.4. Such low albedo values contrast with the high values (~0.8) used in the existing snow schemes of land surface models. The SNICAR radiative transfer model can reproduce the observations that fresh shallow snow has a low albedo value, based on which a fresh snow albedo scheme was derived in this study. Finally, the impact of the fresh snow albedo on snow ablation was examined at 45 meteorological stations on TP using the land surface model Noah-MP which incorporated the new scheme. Allowing albedo to change with snow depth can produce quite realistic snow depths compared with observations. In contrast, the typically assumed fresh snow albedo of 0.82 leads to too large snow depths in the snow ablation period averaged across 45 stations. The shallow snow transparency impact on snow ablation is therefore particularly important in the TP interior, where snow is rather thin and radiation is strong.

Abstract. Geothermal heat flow (GHF) is the dominant factor affecting the basal thermal regime of ice sheet dynamics. But it is poorly defined for the Antarctic ice sheet. We compare the basal thermal state of the Totten Glacier catchment as simulated by eight different GHF datasets. We use a basal energy and water flow model coupled with a 3D full-Stokes ice dynamics model to estimate the basal temperature, basal friction heat and basal melting rate. In addition to the location of subglacial lakes, we use specularity content of the airborne radar returns as a two-sided constraint to discriminate between local wet or dry basal conditions and compare the returns with the basal state simulations with different GHFs. Two medium magnitude GHF distribution maps derived from seismic modelling rank well at simulating both cold- and warm-bed regions, the GHFs from Shen et al. (2020) and Shapiro and Ritzwoller (2004). The best-fit simulated result shows that most of the inland bed area is frozen. Only the central inland subglacial canyon, co-located with high specularity content, reaches the pressure melting point consistently in all the eight GHFs. Modelled basal melting rates in the slow-flowing region are generally 0–5 mm yr−1 but with local maxima of 10 mm yr−1 at the central inland subglacial canyon. The fast-flowing grounded glaciers close to the Totten ice shelf are lubricating their bases with meltwater at rates of 10–400 mm yr−1.

This chapter presents an ecosystem-based framework for applying soil microbiology, ecology, and biochemistry (SMEB) principles and processes to address the preservation and sustainability of global soils to meet societal needs in the face of environmental change. The approach is organized around the UN Sustainable Development Goals, focusing on ecosystem services provided by soil microbes and soil biota at the nexus of food, water, and energy. The role of soil biota in ecosystem processes and the impacts of human activities on those processes are presented. The approach promotes conservation and regenerative methods that manage natural SMEB processes to optimize ecosystem services and minimize alterations in natural processes. Adoption and application of sound SMEB science will require a high degree of literacy among different stakeholders to codevelop management practices and regulatory policy. The approach also advocates promoting SMEB science literacy within the education system through reforms in science standards and curricula.

Ice cores from the relatively low-lying ice caps in Svalbard have not been widely exploited in climatic and environmental studies due to uncertainties about the effect of melt water percolation. However, results from two recent Svalbard ice cores, at Lomonosovfonna (1250 m asl) and Austfonna (750 m asl), have shown that with careful site selection, high-resolution sampling and multiple chemical analyses, it is possible to recover ice cores with partly preserved annual signals. These cores are estimated to cover at least the past 600 years and have been dated using a combination of known reference horizons and glacial modeling. The δ18O data from both Lomonosovfonna and Austfonna ice cores suggest that the 20th century was the warmest during the past 600 years. A comparison of the ice core and sea ice records from this period suggests that sea ice extent and Austfonna δ18O are linked over the past 400 years. This may reflect the position of the storm tracks and their direct influence on the relatively low altitude Austfonna. Lomonosovfonna may be less sensitive to such changes and primarily record atmospheric changes due to its higher elevation. The anthropogenic influence on Svalbard environment is illustrated by increased levels of non-sea-salt sulphate, nitrate, acidity, fly-ash and organic contaminants particularly during the second half of 1900s. Decreased concentrations of some components in recent decades most likely reflect emission and use restrictions. However, some current-use organic pesticide compounds show growing concentrations in near surface layers.

Abstract We make the case for an emergent notion of authenticity of science based on systems theory and neo‐Piagetian thought. We propose that authentic science is an emergent property of a dynamic system of learning precipitated by the interactions among students, teachers, and scientists that occur within the contexts defined by the internal and external constraints of the cultures of the schools and communities within which they operate. Authenticity as an emergent property of the learning process challenges the basis for many science curricula and current pedagogical practices that take scientists' science as their norm and that assume a priori that such is authentic, i.e., it practices preauthentication. We argue that what constitutes authentic science can be taught neither in the traditional didactic modes nor through simulations of scientists' science in the classroom. Instead, authenticity needs to be seen as emergent and as diverse in meaning. To illustrate this point, we draw from two different face‐to‐face, teacher/student–scientist partnership programs. Both studies support a notion of authenticity that emerges as teachers, students, and scientists come to interact, make meaning of, and come to own the activities they engage in collaboratively. We conclude by considering the implications of such an analysis for science education. © 2003 Wiley Periodicals, Inc. J Res Sci Teach 40: 737–756, 2003

In a series of community food webs from native and agricultural soils, we modeled energetics and stability, and evaluated the role of the various groups of organisms and their interactions in energy flow and community stability. Species were aggregated into functional groups based on their trophic position in the food webs. Energy flow rates among the groups were calculated by a model using observations on population sizes, death rates, specific feeding preferences and energy conversion efficiencies. From the energetic organization of the communities we derived the strengths of the mutual effects among the populations. These interaction strengths were found to be patterned in a way that is important to community stability. The patterning consisted of the simultaneous occurrence of strong top down effects at lower trophic levels and strong bottom up effects at higher trophic levels. These patterns resulted directly from the empirical data we used to parameterize the model, as we found no stabilizing patterns with random but plausible parameter values. Also, the impact of each individual interaction on community stability was established. This analysis showed that some interactions had a relatively strong impact on stability, whereas other interactions had only a small impact. These impacts on stability were neither correlated with energy flow nor with interaction strength. Comparison of the seven food webs showed that these impacts were sometimes connected to particular groups of organisms involved in the interaction, but sometimes they were not, which might be due to different trophic positions in the food webs. We argue that future research should be directed to answer the question which energetic properties of the organisms form the basis of the patterning of the interaction strengths, as this would improve our understanding of the interrelationships between energetics, community stability, and hence the maintenance of biological diversity.

Abstract Digital elevation models (DEMs) of the bed and surface of the polythermal Midre Lovénbreen, Svalbard, are used to identify changes in glacier geometry between 1977 and 1995. The calculated mean annual mass balance (−0·61 m water equivalent (w.e.) a −1 ) is more negative than that derived from field measurements (−0·35 m w.e. a −1 ), although the error associated with this value (±0·7 m a −1 ) suggests that the difference may be accounted for by errors. However, similar discrepancies between DEM‐based and field‐based measurements of mass balance have been reported elsewhere in Svalbard. Although errors may be responsible, patterns of surface elevation change may also be explained in terms of patterns of ablation, accumulation, and dynamics. The theoretical structure of the subglacial drainage system is modelled using different assumptions about subglacial water pressure, in 1977 and 1995. These reconstructions are compared with the observed positions of proglacial outlet streams. Decreasing subglacial water pressure results in a decrease in the influence of surface morphology and an increase in the role of the bed topography on drainage routing, which generally leads to more dispersed drainage. Long‐term changes in the position of proglacial outlet streams occur as a result of changes in glacier geometry, but short‐term changes may also occur in response to early season water pressures, controlled by meteorological and hydrological conditions. Copyright © 2003 John Wiley &amp; Sons, Ltd.

A 100‐m ice core from site G 15 (accumulation rate 0.1 m water yr −1 , mean annual temperature −38°C) on the Mizuho plateau, Dronning Maud Land, East Antarctica, has been analysed using the dielectric profiling (DEP) technique. The capacitance and conductance of the core were measured at ac frequencies (20 Hz‐300 kHz). The high‐frequency conductivity profile shows variations that are primarily related to the strong acids derived from volcanic activity. The Tambora (1815) eruption can be identified with the aid of an approximate chronology based on the firn densification rate, other historic eruptions can then be recognised. Beyond about 300‐years historical observations are very few, however if a constant overall accumulation rate is assumed, a well‐known eruption of 1259 A.D. can be found near the bottom of the core. Other peaks in the conductivity profile can then be assigned dates accurate to within a few years. Using the conductivity profile it is possible to estimate the relative acid deposition fluxes produced by the main eruptions with reasonable accuracy. The estimated acid deposisition fluxes realtive to the Tambora (1815) eruption, of Agung (1963) is 27%, Krakatoa (1883), 25%, the signal of 1601, 28%, and that of 1259, 53%.

We examine the quality of atmospherically deposited ion and isotope signals in an ice core taken from a periodically melting ice field, Lomonosovfonna in central Spitsbergen, Svalbard. The aim is to determine the degree to which the signals are altered by periodic melting of the ice. We use three diagnostics: (1) the relation between peak values in the ice chemical and isotopic record and ice facies type, (2) the number of apparent annual cycles in these records compared with independently determined number of years represented in the ice core, and (3) a statistical comparison of the isotopic record in the ice core and the isotope records from coastal stations from the same region. We find that during warm summers, as much as 50% of the annual accumulation may melt and percolate into the firn; in a median year this decreases to ∼25%. As a consequence of percolation, the most mobile acids show up to 50% higher concentrations in bubble‐poor ice facies compared with facies that are less affected by melt. Most of the other chemical species are less affected than the strong acids, and the stable water isotopes show little evidence of mobility. Annual or biannual cycles are detected in most parameters, and the water isotope record has a comparable statistical distribution to isotopic records from coastal stations. We conclude that ice cores from sites like Lomonosovfonna contain a useful environmental record, despite melt events and percolation and that most parameters preserve an annual, or in the worst cases, a biannual atmospheric signal.

EcologyVolume 66, Issue 6 p. 1979-1981 Article Ingestion of Vesicular-arbuscular Mycorrhizal Hyphae and Spores by Soil Microarthropods John C. Moore, John C. MooreSearch for more papers by this authorT. V. St. John, T. V. St. JohnSearch for more papers by this authorD. C. Coleman, D. C. ColemanSearch for more papers by this author John C. Moore, John C. MooreSearch for more papers by this authorT. V. St. John, T. V. St. JohnSearch for more papers by this authorD. C. Coleman, D. C. ColemanSearch for more papers by this author First published: 01 December 1985 https://doi.org/10.2307/2937394Citations: 62AboutRelatedInformationPDFPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessClose modalShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL No abstract is available for this article.Citing Literature Volume66, Issue6December 1985Pages 1979-1981 RelatedInformation RecommendedDo fungivores trigger the transfer of protective metabolites from host plants to arbuscular mycorrhizal hyphae?Marie Duhamel, Roel Pel, Astra Ooms, Heike Bücking, Jan Jansa, Jacintha Ellers, Nico M. van Straalen, Tjalf Wouda, Philippe Vandenkoornhuyse, E. Toby Kiers, EcologyLack of Vesicular‐Arbuscular Mycorrhizal Inoculum in a Ponderosa Pine ForestD. A. Kovacic, T. V. St. John, M. I. Dyer, EcologyDO ARBUSCULAR MYCORRHIZAL FUNGI ALTER PLANT–PATHOGEN RELATIONS?Victoria A. Borowicz, EcologyArbuscular mycorrhizal fungi ameliorate temperature stress in thermophilic plantsRebecca Bunn, Ylva Lekberg, Catherine Zabinski, EcologyPlant species differ in their ability to reduce allocation to non‐beneficial arbuscular mycorrhizal fungiEmily Grman, Ecology

Mycorrhizae occur in nearly all terrestrial ecosystems. Resource exchange between host plants and mycorrhizal fungi influences community, ecosystem, and even global patterns and processes. Understanding the mechanisms and consequences of mycorrhizal symbioses across a hierarchy of scales will help predict system responses to environmental change and facilitate the management of these responses for sustainability and productivity. Conceptual and mathematical models have been developed to help understand and predict mycorrhizal functions. These models are most developed for individual- and population-scale processes, but models at community, ecosystem, and global scales are also beginning to emerge. We review seven types of mycorrhizal models that vary in their scale of resolution and dynamics, and discuss approaches for integrating these models with each other and with general models of terrestrial ecosystems.

Detritus is a central feature in marine, freshwater, and terrestrial ecosystems. Despite the ubiquity of detritus, ecologists have largely ignored its role in influencing food web structure. We used a meta‐analytic approach to ask three questions about how detritus affects food web structure in a wide variety of ecosystems. First, what is the effect strength of detritus on primary producers, detritivores, herbivores, and predators? Second, what functional role does detritus serve for consumers (energetic, habitat, or both)? Third, how does the effect of detritus on consumers vary between aquatic and terrestrial ecosystems? We found that detritus has strong positive effects on primary producers and consumers in a wide range of ecosystems types. Detritus has a positive direct effect on detritivores by providing both an energetic resource and habitat (refuge from predators). Detritus has equally strong positive effects on herbivores and predators, driven by a positive direct effect of habitat. Detritus has positive effects on consumers in both aquatic and terrestrial ecosystems with 1.7 times stronger effects in terrestrial ecosystems. These results suggest that detritus has strong effects on food‐web structure in a variety of ecosystem types. Even the portion of the food web that is linked most strongly to living plant tissue as its primary energy source is strongly positively affected.

Abstract. A particle-based computer simulation model was developed for investigating the dynamics of glaciers. In the model, large ice bodies are made of discrete elastic particles which are bound together by massless elastic beams. These beams can break, which induces brittle behaviour. At loads below fracture, beams may also break and reform with small probabilities to incorporate slowly deforming viscous behaviour in the model. This model has the advantage that it can simulate important physical processes such as ice calving and fracturing in a more realistic way than traditional continuum models. For benchmarking purposes the deformation of an ice block on a slip-free surface was compared to that of a similar block simulated with a Finite Element full-Stokes continuum model. Two simulations were performed: (1) calving of an ice block partially supported in water, similar to a grounded marine glacier terminus, and (2) fracturing of an ice block on an inclined plane of varying basal friction, which could represent transition to fast flow or surging. Despite several approximations, including restriction to two-dimensions and simplified water-ice interaction, the model was able to reproduce the size distributions of the debris observed in calving, which may be approximated by universal scaling laws. On a moderate slope, a large ice block was stable and quiescent as long as there was enough of friction against the substrate. For a critical length of frictional contact, global sliding began, and the model block disintegrated in a manner suggestive of a surging glacier. In this case the fragment size distribution produced was typical of a grinding process.

The US Long Term Ecological Research (LTER) Network enters its fourth decade with a distinguished record of achievement in ecological science. The value of long-term observations and experiments has never been more important for testing ecological theory and for addressing today's most difficult environmental challenges. The network's potential for tackling emergent continent-scale questions such as cryosphere loss and landscape change is becoming increasingly apparent on the basis of a capacity to combine long-term observations and experimental results with new observatory-based measurements, to study socioecological systems, to advance the use of environmental cyberinfrastructure, to promote environmental science literacy, and to engage with decisionmakers in framing major directions for research. The long-term context of network science, from understanding the past to forecasting the future, provides a valuable perspective for helping to solve many of the crucial environmental problems facing society today.

Abstract We analyze simulated sea ice changes in eight different Earth System Models that have conducted experiment G1 of the Geoengineering Model Intercomparison Project (GeoMIP). The simulated response of balancing abrupt quadrupling of CO 2 (abrupt4xCO2) with reduced shortwave radiation successfully moderates annually averaged Arctic temperature rise to about 1°C, with modest changes in seasonal sea ice cycle compared with the preindustrial control simulations (piControl). Changes in summer and autumn sea ice extent are spatially correlated with temperature patterns but much less in winter and spring seasons. However, there are changes of ±20% in sea ice concentration in all seasons, and these will induce changes in atmospheric circulation patterns. In summer and autumn, the models consistently simulate less sea ice relative to preindustrial simulations in the Beaufort, Chukchi, East Siberian, and Laptev Seas, and some models show increased sea ice in the Barents/Kara Seas region. Sea ice extent increases in the Greenland Sea, particularly in winter and spring and is to some extent associated with changed sea ice drift. Decreased sea ice cover in winter and spring in the Barents Sea is associated with increased cyclonic activity entering this area under G1. In comparison, the abrupt4xCO2 experiment shows almost total sea ice loss in September and strong correlation with regional temperatures in all seasons consistent with open ocean conditions. The tropospheric circulation displays a Pacific North America pattern‐like anomaly with negative phase in G1‐piControl and positive phase under abrupt4xCO2‐piControl.

Abstract Realistic projection of future climate‐carbon (C) cycle feedbacks requires better understanding and an improved representation of the C cycle in permafrost regions in the current generation of Earth system models. Here we evaluated 10 terrestrial ecosystem models for their estimates of net primary productivity (NPP) and responses to historical climate change in permafrost regions in the Northern Hemisphere. In comparison with the satellite estimate from the Moderate Resolution Imaging Spectroradiometer (MODIS; 246 ± 6 g C m −2 yr −1 ), most models produced higher NPP (309 ± 12 g C m −2 yr −1 ) over the permafrost region during 2000–2009. By comparing the simulated gross primary productivity (GPP) with a flux tower‐based database, we found that although mean GPP among the models was only overestimated by 10% over 1982–2009, there was a twofold discrepancy among models (380 to 800 g C m −2 yr −1 ), which mainly resulted from differences in simulated maximum monthly GPP (GPP max ). Most models overestimated C use efficiency (CUE) as compared to observations at both regional and site levels. Further analysis shows that model variability of GPP and CUE are nonlinearly correlated to variability in specific leaf area and the maximum rate of carboxylation by the enzyme Rubisco at 25°C ( V c max_25 ), respectively. The models also varied in their sensitivities of NPP, GPP, and CUE to historical changes in climate and atmospheric CO 2 concentration. These results indicate that model predictive ability of the C cycle in permafrost regions can be improved by better representation of the processes controlling CUE and GPP max as well as their sensitivity to climate change.

We evaluate the effectiveness and the regional inequalities of solar radiation management (SRM) in compensating for simultaneous changes in temperature and precipitation caused by increased greenhouse gas concentrations. We analyze the results from Earth System Models under four Geoengineering Model Intercomparison Project (GeoMIP) experiments with a modified form of the Residual Climate Response approach. Each experiment produces 50 model yrs of simulations: 13 models completed experiment G1 (offsetting 4 × CO2 via solar reduction); 12 models completed experiment G2 (offsetting CO2 that increased by 1% per year); 3 models completed experiment G3 (offsetting increasing radiative forcing under RCP4.5 with increasing stratospheric aerosol); and 7 models completed experiment G4 (injection of 5 Tg SO2 a− 1 into the stratosphere). The regional inequalities in temperature and precipitation compensation for experiments G1, G3 and G4 are significantly different from their corresponding noise backgrounds for most models, but for G2 they are not significantly different from noise. Differences in the regional inequalities and the actual effectiveness among the four SRM scenarios are not significant for many models. However, in more than half of the models, the effectiveness for temperature in the solar dimming geoengineering scenarios (G1 and G2) is significantly higher than that in the SO2 geoengineering scenarios (G3 and G4). The effectiveness of the four SRM experiments in compensating for temperature change is considerably higher than for precipitation. The methodology used highlights that a large across-model variation in the treatment of key geoengineering processes (such as stratospheric aerosols) and the quantification of damage caused by climate change creates significant uncertainties in any strategies to achieve optimal compensation effectiveness across different regions.

Abstract. A realistic simulation of snow cover and its thermal properties are important for accurate modelling of permafrost. We analyse simulated relationships between air and near-surface (20 cm) soil temperatures in the Northern Hemisphere permafrost region during winter, with a particular focus on snow insulation effects in nine land surface models, and compare them with observations from 268 Russian stations. There are large cross-model differences in the simulated differences between near-surface soil and air temperatures (ΔT; 3 to 14 °C), in the sensitivity of soil-to-air temperature (0.13 to 0.96 °C °C−1), and in the relationship between ΔT and snow depth. The observed relationship between ΔT and snow depth can be used as a metric to evaluate the effects of each model's representation of snow insulation, hence guide improvements to the model's conceptual structure and process parameterisations. Models with better performance apply multilayer snow schemes and consider complex snow processes. Some models show poor performance in representing snow insulation due to underestimation of snow depth and/or overestimation of snow conductivity. Generally, models identified as most acceptable with respect to snow insulation simulate reasonable areas of near-surface permafrost (13.19 to 15.77 million km2). However, there is not a simple relationship between the sophistication of the snow insulation in the acceptable models and the simulated area of Northern Hemisphere near-surface permafrost, because several other factors, such as soil depth used in the models, the treatment of soil organic matter content, hydrology and vegetation cover, also affect the simulated permafrost distribution.