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Showing papers on "Climate change published in 2018"


Journal ArticleDOI
TL;DR: The risk that self-reinforcing feedbacks could push the Earth System toward a planetary threshold that, if crossed, could prevent stabilization of the climate at intermediate temperature rises and cause continued warming on a “Hothouse Earth” pathway even as human emissions are reduced is explored.
Abstract: We explore the risk that self-reinforcing feedbacks could push the Earth System toward a planetary threshold that, if crossed, could prevent stabilization of the climate at intermediate temperature rises and cause continued warming on a "Hothouse Earth" pathway even as human emissions are reduced. Crossing the threshold would lead to a much higher global average temperature than any interglacial in the past 1.2 million years and to sea levels significantly higher than at any time in the Holocene. We examine the evidence that such a threshold might exist and where it might be. If the threshold is crossed, the resulting trajectory would likely cause serious disruptions to ecosystems, society, and economies. Collective human action is required to steer the Earth System away from a potential threshold and stabilize it in a habitable interglacial-like state. Such action entails stewardship of the entire Earth System-biosphere, climate, and societies-and could include decarbonization of the global economy, enhancement of biosphere carbon sinks, behavioral changes, technological innovations, new governance arrangements, and transformed social values.

1,685 citations


Journal ArticleDOI
05 Jan 2018-Science
TL;DR: Improved numerical models of oceanographic processes that control oxygen depletion and the large-scale influence of altered biogeochemical cycles are needed to better predict the magnitude and spatial patterns of deoxygenation in the open ocean, as well as feedbacks to climate.
Abstract: BACKGROUND Oxygen concentrations in both the open ocean and coastal waters have been declining since at least the middle of the 20th century. This oxygen loss, or deoxygenation, is one of the most important changes occurring in an ocean increasingly modified by human activities that have raised temperatures, CO 2 levels, and nutrient inputs and have altered the abundances and distributions of marine species. Oxygen is fundamental to biological and biogeochemical processes in the ocean. Its decline can cause major changes in ocean productivity, biodiversity, and biogeochemical cycles. Analyses of direct measurements at sites around the world indicate that oxygen-minimum zones in the open ocean have expanded by several million square kilometers and that hundreds of coastal sites now have oxygen concentrations low enough to limit the distribution and abundance of animal populations and alter the cycling of important nutrients. ADVANCES In the open ocean, global warming, which is primarily caused by increased greenhouse gas emissions, is considered the primary cause of ongoing deoxygenation. Numerical models project further oxygen declines during the 21st century, even with ambitious emission reductions. Rising global temperatures decrease oxygen solubility in water, increase the rate of oxygen consumption via respiration, and are predicted to reduce the introduction of oxygen from the atmosphere and surface waters into the ocean interior by increasing stratification and weakening ocean overturning circulation. In estuaries and other coastal systems strongly influenced by their watershed, oxygen declines have been caused by increased loadings of nutrients (nitrogen and phosphorus) and organic matter, primarily from agriculture; sewage; and the combustion of fossil fuels. In many regions, further increases in nitrogen discharges to coastal waters are projected as human populations and agricultural production rise. Climate change exacerbates oxygen decline in coastal systems through similar mechanisms as those in the open ocean, as well as by increasing nutrient delivery from watersheds that will experience increased precipitation. Expansion of low-oxygen zones can increase production of N 2 O, a potent greenhouse gas; reduce eukaryote biodiversity; alter the structure of food webs; and negatively affect food security and livelihoods. Both acidification and increasing temperature are mechanistically linked with the process of deoxygenation and combine with low-oxygen conditions to affect biogeochemical, physiological, and ecological processes. However, an important paradox to consider in predicting large-scale effects of future deoxygenation is that high levels of productivity in nutrient-enriched coastal systems and upwelling areas associated with oxygen-minimum zones also support some of the world’s most prolific fisheries. OUTLOOK Major advances have been made toward understanding patterns, drivers, and consequences of ocean deoxygenation, but there is a need to improve predictions at large spatial and temporal scales important to ecosystem services provided by the ocean. Improved numerical models of oceanographic processes that control oxygen depletion and the large-scale influence of altered biogeochemical cycles are needed to better predict the magnitude and spatial patterns of deoxygenation in the open ocean, as well as feedbacks to climate. Developing and verifying the next generation of these models will require increased in situ observations and improved mechanistic understanding on a variety of scales. Models useful for managing nutrient loads can simulate oxygen loss in coastal waters with some skill, but their ability to project future oxygen loss is often hampered by insufficient data and climate model projections on drivers at appropriate temporal and spatial scales. Predicting deoxygenation-induced changes in ecosystem services and human welfare requires scaling effects that are measured on individual organisms to populations, food webs, and fisheries stocks; considering combined effects of deoxygenation and other ocean stressors; and placing an increased research emphasis on developing nations. Reducing the impacts of other stressors may provide some protection to species negatively affected by low-oxygen conditions. Ultimately, though, limiting deoxygenation and its negative effects will necessitate a substantial global decrease in greenhouse gas emissions, as well as reductions in nutrient discharges to coastal waters.

1,469 citations


Journal ArticleDOI
Corinne Le Quéré1, Robbie M. Andrew, Pierre Friedlingstein2, Stephen Sitch2, Judith Hauck3, Julia Pongratz4, Julia Pongratz5, Penelope A. Pickers1, Jan Ivar Korsbakken, Glen P. Peters, Josep G. Canadell6, Almut Arneth7, Vivek K. Arora, Leticia Barbero8, Leticia Barbero9, Ana Bastos4, Laurent Bopp10, Frédéric Chevallier11, Louise Chini12, Philippe Ciais11, Scott C. Doney13, Thanos Gkritzalis14, Daniel S. Goll11, Ian Harris1, Vanessa Haverd6, Forrest M. Hoffman15, Mario Hoppema3, Richard A. Houghton16, George C. Hurtt12, Tatiana Ilyina5, Atul K. Jain17, Truls Johannessen18, Chris D. Jones19, Etsushi Kato, Ralph F. Keeling20, Kees Klein Goldewijk21, Kees Klein Goldewijk22, Peter Landschützer5, Nathalie Lefèvre23, Sebastian Lienert24, Zhu Liu1, Zhu Liu25, Danica Lombardozzi26, Nicolas Metzl23, David R. Munro27, Julia E. M. S. Nabel5, Shin-Ichiro Nakaoka28, Craig Neill29, Craig Neill30, Are Olsen18, T. Ono, Prabir K. Patra31, Anna Peregon11, Wouter Peters32, Wouter Peters33, Philippe Peylin11, Benjamin Pfeil34, Benjamin Pfeil18, Denis Pierrot8, Denis Pierrot9, Benjamin Poulter35, Gregor Rehder36, Laure Resplandy37, Eddy Robertson19, Matthias Rocher11, Christian Rödenbeck5, Ute Schuster2, Jörg Schwinger34, Roland Séférian11, Ingunn Skjelvan34, Tobias Steinhoff38, Adrienne J. Sutton39, Pieter P. Tans39, Hanqin Tian40, Bronte Tilbrook29, Bronte Tilbrook30, Francesco N. Tubiello41, Ingrid T. van der Laan-Luijkx33, Guido R. van der Werf42, Nicolas Viovy11, Anthony P. Walker15, Andy Wiltshire19, Rebecca Wright1, Sönke Zaehle5, Bo Zheng11 
University of East Anglia1, University of Exeter2, Alfred Wegener Institute for Polar and Marine Research3, Ludwig Maximilian University of Munich4, Max Planck Society5, Commonwealth Scientific and Industrial Research Organisation6, Karlsruhe Institute of Technology7, Atlantic Oceanographic and Meteorological Laboratory8, Cooperative Institute for Marine and Atmospheric Studies9, École Normale Supérieure10, Centre national de la recherche scientifique11, University of Maryland, College Park12, University of Virginia13, Flanders Marine Institute14, Oak Ridge National Laboratory15, Woods Hole Research Center16, University of Illinois at Urbana–Champaign17, Geophysical Institute, University of Bergen18, Met Office19, University of California, San Diego20, Utrecht University21, Netherlands Environmental Assessment Agency22, University of Paris23, Oeschger Centre for Climate Change Research24, Tsinghua University25, National Center for Atmospheric Research26, Institute of Arctic and Alpine Research27, National Institute for Environmental Studies28, Cooperative Research Centre29, Hobart Corporation30, Japan Agency for Marine-Earth Science and Technology31, University of Groningen32, Wageningen University and Research Centre33, Bjerknes Centre for Climate Research34, Goddard Space Flight Center35, Leibniz Institute for Baltic Sea Research36, Princeton University37, Leibniz Institute of Marine Sciences38, National Oceanic and Atmospheric Administration39, Auburn University40, Food and Agriculture Organization41, VU University Amsterdam42
TL;DR: In this article, the authors describe data sets and methodology to quantify the five major components of the global carbon budget and their uncertainties, including emissions from land use and land-use change data and bookkeeping models.
Abstract: . Accurate assessment of anthropogenic carbon dioxide ( CO2 ) emissions and their redistribution among the atmosphere, ocean, and terrestrial biosphere – the “global carbon budget” – is important to better understand the global carbon cycle, support the development of climate policies, and project future climate change. Here we describe data sets and methodology to quantify the five major components of the global carbon budget and their uncertainties. Fossil CO2 emissions ( EFF ) are based on energy statistics and cement production data, while emissions from land use and land-use change ( ELUC ), mainly deforestation, are based on land use and land-use change data and bookkeeping models. Atmospheric CO2 concentration is measured directly and its growth rate ( GATM ) is computed from the annual changes in concentration. The ocean CO2 sink ( SOCEAN ) and terrestrial CO2 sink ( SLAND ) are estimated with global process models constrained by observations. The resulting carbon budget imbalance ( BIM ), the difference between the estimated total emissions and the estimated changes in the atmosphere, ocean, and terrestrial biosphere, is a measure of imperfect data and understanding of the contemporary carbon cycle. All uncertainties are reported as ±1σ . For the last decade available (2008–2017), EFF was 9.4±0.5 GtC yr −1 , ELUC 1.5±0.7 GtC yr −1 , GATM 4.7±0.02 GtC yr −1 , SOCEAN 2.4±0.5 GtC yr −1 , and SLAND 3.2±0.8 GtC yr −1 , with a budget imbalance BIM of 0.5 GtC yr −1 indicating overestimated emissions and/or underestimated sinks. For the year 2017 alone, the growth in EFF was about 1.6 % and emissions increased to 9.9±0.5 GtC yr −1 . Also for 2017, ELUC was 1.4±0.7 GtC yr −1 , GATM was 4.6±0.2 GtC yr −1 , SOCEAN was 2.5±0.5 GtC yr −1 , and SLAND was 3.8±0.8 GtC yr −1 , with a BIM of 0.3 GtC. The global atmospheric CO2 concentration reached 405.0±0.1 ppm averaged over 2017. For 2018, preliminary data for the first 6–9 months indicate a renewed growth in EFF of + 2.7 % (range of 1.8 % to 3.7 %) based on national emission projections for China, the US, the EU, and India and projections of gross domestic product corrected for recent changes in the carbon intensity of the economy for the rest of the world. The analysis presented here shows that the mean and trend in the five components of the global carbon budget are consistently estimated over the period of 1959–2017, but discrepancies of up to 1 GtC yr −1 persist for the representation of semi-decadal variability in CO2 fluxes. A detailed comparison among individual estimates and the introduction of a broad range of observations show (1) no consensus in the mean and trend in land-use change emissions, (2) a persistent low agreement among the different methods on the magnitude of the land CO2 flux in the northern extra-tropics, and (3) an apparent underestimation of the CO2 variability by ocean models, originating outside the tropics. This living data update documents changes in the methods and data sets used in this new global carbon budget and the progress in understanding the global carbon cycle compared with previous publications of this data set (Le Quere et al., 2018, 2016, 2015a, b, 2014, 2013). All results presented here can be downloaded from https://doi.org/10.18160/GCP-2018 .

1,458 citations


Journal ArticleDOI
08 Aug 2018-Nature
TL;DR: Satellite data for the period 1982–2016 reveal changes in land use and land cover at global and regional scales that reflect patterns of land change indicative of a human-dominated Earth system.
Abstract: Land change is a cause and consequence of global environmental change1,2. Changes in land use and land cover considerably alter the Earth’s energy balance and biogeochemical cycles, which contributes to climate change and—in turn—affects land surface properties and the provision of ecosystem services1–4. However, quantification of global land change is lacking. Here we analyse 35 years’ worth of satellite data and provide a comprehensive record of global land-change dynamics during the period 1982–2016. We show that—contrary to the prevailing view that forest area has declined globally5—tree cover has increased by 2.24 million km2 (+7.1% relative to the 1982 level). This overall net gain is the result of a net loss in the tropics being outweighed by a net gain in the extratropics. Global bare ground cover has decreased by 1.16 million km2 (−3.1%), most notably in agricultural regions in Asia. Of all land changes, 60% are associated with direct human activities and 40% with indirect drivers such as climate change. Land-use change exhibits regional dominance, including tropical deforestation and agricultural expansion, temperate reforestation or afforestation, cropland intensification and urbanization. Consistently across all climate domains, montane systems have gained tree cover and many arid and semi-arid ecosystems have lost vegetation cover. The mapped land changes and the driver attributions reflect a human-dominated Earth system. The dataset we developed may be used to improve the modelling of land-use changes, biogeochemical cycles and vegetation–climate interactions to advance our understanding of global environmental change1–4,6. Satellite data for the period 1982–2016 reveal changes in land use and land cover at global and regional scales that reflect patterns of land change indicative of a human-dominated Earth system.

1,096 citations


Journal ArticleDOI
16 May 2018-Nature
TL;DR: Analysis of 2002–2016 GRACE satellite observations of terrestrial water storage reveals substantial changes in freshwater resources globally, which are driven by natural and anthropogenic climate variability and human activities.
Abstract: Freshwater availability is changing worldwide. Here we quantify 34 trends in terrestrial water storage observed by the Gravity Recovery and Climate Experiment (GRACE) satellites during 2002–2016 and categorize their drivers as natural interannual variability, unsustainable groundwater consumption, climate change or combinations thereof. Several of these trends had been lacking thorough investigation and attribution, including massive changes in northwestern China and the Okavango Delta. Others are consistent with climate model predictions. This observation-based assessment of how the world’s water landscape is responding to human impacts and climate variations provides a blueprint for evaluating and predicting emerging threats to water and food security.

966 citations



Journal ArticleDOI
Andrew Shepherd1, Erik R. Ivins2, Eric Rignot3, Ben Smith4, Michiel R. van den Broeke, Isabella Velicogna3, Pippa L. Whitehouse5, Kate Briggs1, Ian Joughin4, Gerhard Krinner6, Sophie Nowicki7, Tony Payne8, Ted Scambos9, Nicole Schlegel2, Geruo A3, Cécile Agosta, Andreas P. Ahlstrøm10, Greg Babonis11, Valentina R. Barletta12, Alejandro Blazquez, Jennifer Bonin13, Beata Csatho11, Richard I. Cullather7, Denis Felikson14, Xavier Fettweis, René Forsberg12, Hubert Gallée6, Alex S. Gardner2, Lin Gilbert15, Andreas Groh16, Brian Gunter17, Edward Hanna18, Christopher Harig19, Veit Helm20, Alexander Horvath21, Martin Horwath16, Shfaqat Abbas Khan12, Kristian K. Kjeldsen10, Hannes Konrad1, Peter L. Langen22, Benoit S. Lecavalier23, Bryant D. Loomis7, Scott B. Luthcke7, Malcolm McMillan1, Daniele Melini24, Sebastian H. Mernild25, Sebastian H. Mernild26, Sebastian H. Mernild27, Yara Mohajerani3, Philip Moore28, Jeremie Mouginot6, Jeremie Mouginot3, Gorka Moyano, Alan Muir15, Thomas Nagler, Grace A. Nield5, Johan Nilsson2, Brice Noël, Ines Otosaka1, Mark E. Pattle, W. Richard Peltier29, Nadege Pie14, Roelof Rietbroek30, Helmut Rott, Louise Sandberg-Sørensen12, Ingo Sasgen20, Himanshu Save14, Bernd Scheuchl3, Ernst Schrama31, Ludwig Schröder16, Ki-Weon Seo32, Sebastian B. Simonsen12, Thomas Slater1, Giorgio Spada33, T. C. Sutterley3, Matthieu Talpe9, Lev Tarasov23, Willem Jan van de Berg, Wouter van der Wal31, Melchior van Wessem, Bramha Dutt Vishwakarma34, David N. Wiese2, Bert Wouters 
14 Jun 2018-Nature
TL;DR: This work combines satellite observations of its changing volume, flow and gravitational attraction with modelling of its surface mass balance to show that the Antarctic Ice Sheet lost 2,720 ± 1,390 billion tonnes of ice between 1992 and 2017, which corresponds to an increase in mean sea level of 7.6‚¬3.9 millimetres.
Abstract: The Antarctic Ice Sheet is an important indicator of climate change and driver of sea-level rise. Here we combine satellite observations of its changing volume, flow and gravitational attraction with modelling of its surface mass balance to show that it lost 2,720 ± 1,390 billion tonnes of ice between 1992 and 2017, which corresponds to an increase in mean sea level of 7.6 ± 3.9 millimetres (errors are one standard deviation). Over this period, ocean-driven melting has caused rates of ice loss from West Antarctica to increase from 53 ± 29 billion to 159 ± 26 billion tonnes per year; ice-shelf collapse has increased the rate of ice loss from the Antarctic Peninsula from 7 ± 13 billion to 33 ± 16 billion tonnes per year. We find large variations in and among model estimates of surface mass balance and glacial isostatic adjustment for East Antarctica, with its average rate of mass gain over the period 1992–2017 (5 ± 46 billion tonnes per year) being the least certain.

725 citations


Journal ArticleDOI
26 Jul 2018-Nature
TL;DR: A synopsis of the current understanding of the spatio-temporal complexity of this important climate mode and its influence on the Earth system is provided and a unifying framework that identifies the key factors for this complexity is proposed.
Abstract: El Nino events are characterized by surface warming of the tropical Pacific Ocean and weakening of equatorial trade winds that occur every few years Such conditions are accompanied by changes in atmospheric and oceanic circulation, affecting global climate, marine and terrestrial ecosystems, fisheries and human activities The alternation of warm El Nino and cold La Nina conditions, referred to as the El Nino–Southern Oscillation (ENSO), represents the strongest year-to-year fluctuation of the global climate system Here we provide a synopsis of our current understanding of the spatio-temporal complexity of this important climate mode and its influence on the Earth system

598 citations


Journal ArticleDOI
TL;DR: This article investigated future changes in dry-to-wet events using the Community Earth System Model Large Ensemble of climate model simulations and found that anthropogenic forcing yields large twenty-first-century increases in the frequency of wet extremes, including a more than threefold increase in sub-seasonal events comparable to California's 'Great Flood of 1862' and small but statistically robust increases in dry extremes are also apparent.
Abstract: Mediterranean climate regimes are particularly susceptible to rapid shifts between drought and flood—of which, California’s rapid transition from record multi-year dryness between 2012 and 2016 to extreme wetness during the 2016–2017 winter provides a dramatic example. Projected future changes in such dry-to-wet events, however, remain inadequately quantified, which we investigate here using the Community Earth System Model Large Ensemble of climate model simulations. Anthropogenic forcing is found to yield large twenty-first-century increases in the frequency of wet extremes, including a more than threefold increase in sub-seasonal events comparable to California’s ‘Great Flood of 1862’. Smaller but statistically robust increases in dry extremes are also apparent. As a consequence, a 25% to 100% increase in extreme dry-to-wet precipitation events is projected, despite only modest changes in mean precipitation. Such hydrological cycle intensification would seriously challenge California’s existing water storage, conveyance and flood control infrastructure.

529 citations


Journal ArticleDOI
TL;DR: In this paper, the authors examined the ongoing loss of Arctic sea ice across all seasons and found that recent anomalies in spring and winter sea ice coverage have been more significant than any observed drop in summer sea ice extent.
Abstract: The decline in the floating sea ice cover in the Arctic is one of the most striking manifestations of climate change In this review, we examine this ongoing loss of Arctic sea ice across all seasons Our analysis is based on satellite retrievals, atmospheric reanalysis, climate-model simulations and a literature review We find that relative to the 1981–2010 reference period, recent anomalies in spring and winter sea ice coverage have been more significant than any observed drop in summer sea ice extent (SIE) throughout the satellite period For example, the SIE in May and November 2016 was almost four standard deviations below the reference SIE in these months Decadal ice loss during winter months has accelerated from −24 %/decade from 1979 to 1999 to −34%/decade from 2000 onwards We also examine regional ice loss and find that for any given region, the seasonal ice loss is larger the closer that region is to the seasonal outer edge of the ice cover Finally, across all months, we identify a robust linear relationship between pan-Arctic SIE and total anthropogenic CO₂ emissions The annual cycle of Arctic sea ice loss per ton of CO₂ emissions ranges from slightly above 1 m² throughout winter to more than 3 m² throughout summer Based on a linear extrapolation of these trends, we find the Arctic Ocean will become sea-ice free throughout August and September for an additional 800 ± 300 Gt of CO₂ emissions, while it becomes ice free from July to October for an additional 1400 ± 300 Gt of CO₂ emissions

518 citations


Journal ArticleDOI
04 Apr 2018-Nature
TL;DR: Analysis of changes in plant species richness on mountain summits over the past 145 years suggests that increased climatic warming has led to an acceleration in species richness increase, strikingly synchronized with accelerated global warming.
Abstract: Globally accelerating trends in societal development and human environmental impacts since the mid-twentieth century 1–7 are known as the Great Acceleration and have been discussed as a key indicator of the onset of the Anthropocene epoch 6 . While reports on ecological responses (for example, changes in species range or local extinctions) to the Great Acceleration are multiplying 8, 9 , it is unknown whether such biotic responses are undergoing a similar acceleration over time. This knowledge gap stems from the limited availability of time series data on biodiversity changes across large temporal and geographical extents. Here we use a dataset of repeated plant surveys from 302 mountain summits across Europe, spanning 145 years of observation, to assess the temporal trajectory of mountain biodiversity changes as a globally coherent imprint of the Anthropocene. We find a continent-wide acceleration in the rate of increase in plant species richness, with five times as much species enrichment between 2007 and 2016 as fifty years ago, between 1957 and 1966. This acceleration is strikingly synchronized with accelerated global warming and is not linked to alternative global change drivers. The accelerating increases in species richness on mountain summits across this broad spatial extent demonstrate that acceleration in climate-induced biotic change is occurring even in remote places on Earth, with potentially far-ranging consequences not only for biodiversity, but also for ecosystem functioning and services.

Journal ArticleDOI
TL;DR: This study revealed different responses of tree species to projected climate change, including "winners" and "losers", and the threat level was highest for species that currently have the northernmost distribution centers.
Abstract: Although numerous species distribution models have been developed, most were based on insufficient distribution data or used older climate change scenarios. We aimed to quantify changes in projected ranges and threat level by the years 2061-2080, for 12 European forest tree species under three climate change scenarios. We combined tree distribution data from the Global Biodiversity Information Facility, EUFORGEN and forest inventories, and we developed species distribution models using MaxEnt and 19 bioclimatic variables. Models were developed for three climate change scenarios – optimistic (RCP2.6), moderate (RCP4.5) and pessimistic (RPC8.5) – using three General Circulation Models, for the period 2061-2080. Our study revealed different responses of tree species to projected climate change. The species may be divided into three groups: “winners” – mostly late-successional species: Abies alba, Fagus sylvatica, Fraxinus excelsior, Quercus robur and Q. petraea; “losers” – mostly pioneer species: Betula pendula, Larix decidua, Picea abies and Pinus sylvestris and alien species – Pseudotsuga menziesii, Q. rubra and Robinia pseudoacacia, which may be also considered as “winners”. Assuming limited migration, most of the species studied would face significant decrease of suitable habitat area. The threat level was highest for species that currently have the northernmost distribution centers. Ecological consequences of the projected range contractions would be serious for both forest management and nature conservation. This article is protected by copyright. All rights reserved.

Journal ArticleDOI
TL;DR: In this article, a significant update of Bio-ORACLE for new future climate scenarios, present-day conditions and benthic layers (near sea bottom) is presented, where the reliability of data layers is assessed using a cross-validation framework against in situ quality-controlled data.
Abstract: Motivation: The availability of user-friendly, high-resolution global environmental datasets is crucial for bioclimatic modelling. For terrestrial environments, WorldClim has served this purpose since 2005, but equivalent marine data only became available in 2012, with pioneer initiatives like Bio-ORACLE providing data layers for several ecologically relevant variables. Currently, the available marine data packages have not yet been updated to the most recent Intergovernmental Panel on Climate Change (IPCC) predictions nor to present times, and are mostly restricted to the top surface layer of the oceans, precluding the modelling of a large fraction of the benthic diversity that inhabits deeper habitats. To address this gap, we present a significant update of Bio-ORACLE for new future climate scenarios, present-day conditions and benthic layers (near sea bottom). The reliability of data layers was assessed using a cross-validation framework against in situ quality-controlled data. This test showed a generally good agreement between our data layers and the global climatic patterns. We also provide a package of functions in the R software environment (sdmpredictors) to facilitate listing, extraction and management of data layers and allow easy integration with the available pipelines for bioclimatic modelling. Main types of variable contained: Surface and benthic layers for water temperature, salinity, nutrients, chlorophyll, sea ice, current velocity, phytoplankton, primary productivity, iron and light at bottom. Spatial location and grain: Global at 5 arcmin (c.0.08 degrees or 9.2 km at the equator). Time period and grain: Present (2000-2014) and future (2040-2050 and 2090-2100) environmental conditions based on monthly averages. Major taxa and level of measurement: Marine biodiversity associated with sea surface and epibenthic habitats. Software format: ASCII and TIFF grid formats for geographical information systems and a package of functions developed for R software.

Journal ArticleDOI
TL;DR: In this article, a transdisciplinary approach is proposed to identify demand-side climate solutions, investigate their mitigation potential, detail policy measures and assess their implications for well-being, and propose a trans-disciplinary approach to identify and analyse demand side climate solutions.
Abstract: Research on climate change mitigation tends to focus on supply-side technology solutions A better understanding of demand-side solutions is missing We propose a transdisciplinary approach to identify demand-side climate solutions, investigate their mitigation potential, detail policy measures and assess their implications for well-being

Journal ArticleDOI
01 Jan 2018
TL;DR: In this article, the authors quantify the magnitude of these twin challenges to urban water security, combining a dataset of urban water sources of 482 of the world's largest cities with estimates of future water demand, based on the Intergovernmental Panel on Climate Change (IPCC)s Fifth Assessment scenarios, and predictions of water availability, using the WaterGAP3 modelling framework.
Abstract: Urban water demand will increase by 80% by 2050, while climate change will alter the timing and distribution of water. Here we quantify the magnitude of these twin challenges to urban water security, combining a dataset of urban water sources of 482 of the world’s largest cities with estimates of future water demand, based on the Intergovernmental Panel on Climate Change (IPCC)’s Fifth Assessment scenarios, and predictions of future water availability, using the WaterGAP3 modelling framework. We project an urban surface-water deficit of 1,386–6,764 million m³. More than 27% of cities studied, containing 233 million people, will have water demands that exceed surface-water availability. An additional 19% of cities, which are dependent on surface-water transfers, have a high potential for conflict between the urban and agricultural sectors, since both sectors cannot obtain their estimated future water demands. In 80% of these high-conflict watersheds, improvements in agricultural water-use efficiency could free up enough water for urban use. Investments in improving agricultural water use could thus serve as an important global change adaptation strategy. Rising population and changes in water supply under climate change affect cities globally. This study finds that in 27% of cities studied, water demand is likely to exceed availability by 2050, with many other cities competing with agriculture on water needs.

Journal ArticleDOI
TL;DR: A multi-regional dataset of 1485 sites across 52 wildfires from the US Rocky Mountains was used to ask if and how changing climate over the last several decades impacted post-fire tree regeneration, a key indicator of forest resilience.
Abstract: Forest resilience to climate change is a global concern given the potential effects of increased disturbance activity, warming temperatures and increased moisture stress on plants. We used a multi-regional dataset of 1485 sites across 52 wildfires from the US Rocky Mountains to ask if and how changing climate over the last several decades impacted post-fire tree regeneration, a key indicator of forest resilience. Results highlight significant decreases in tree regeneration in the 21st century. Annual moisture deficits were significantly greater from 2000 to 2015 as compared to 1985–1999, suggesting increasingly unfavourable post-fire growing conditions, corresponding to significantly lower seedling densities and increased regeneration failure. Dry forests that already occur at the edge of their climatic tolerance are most prone to conversion to non-forests after wildfires. Major climate-induced reduction in forest density and extent has important consequences for a myriad of ecosystem services now and in the future.

Journal ArticleDOI
Anne D. Bjorkman1, Anne D. Bjorkman2, Isla H. Myers-Smith1, Sarah C. Elmendorf3, Sarah C. Elmendorf4, Sarah C. Elmendorf5, Signe Normand2, Nadja Rüger6, Pieter S. A. Beck, Anne Blach-Overgaard2, Daan Blok7, J. Hans C. Cornelissen8, Bruce C. Forbes9, Damien Georges1, Scott J. Goetz10, Kevin C. Guay11, Gregory H. R. Henry12, Janneke HilleRisLambers13, Robert D. Hollister14, Dirk Nikolaus Karger15, Jens Kattge16, Peter Manning, Janet S. Prevéy, Christian Rixen, Gabriela Schaepman-Strub17, Haydn J.D. Thomas1, Mark Vellend18, Martin Wilmking19, Sonja Wipf, Michele Carbognani20, Luise Hermanutz21, Esther Lévesque22, Ulf Molau23, Alessandro Petraglia20, Nadejda A. Soudzilovskaia24, Marko J. Spasojevic25, Marcello Tomaselli20, Tage Vowles23, Juha M. Alatalo26, Heather D. Alexander27, Alba Anadon-Rosell28, Alba Anadon-Rosell19, Sandra Angers-Blondin1, Mariska te Beest29, Mariska te Beest30, Logan T. Berner10, Robert G. Björk23, Agata Buchwal31, Agata Buchwal32, Allan Buras33, Katherine S. Christie34, Elisabeth J. Cooper35, Stefan Dullinger36, Bo Elberling37, Anu Eskelinen38, Anu Eskelinen39, Esther R. Frei15, Esther R. Frei12, Oriol Grau40, Paul Grogan41, Martin Hallinger, Karen A. Harper42, Monique M. P. D. Heijmans33, James I. Hudson, Karl Hülber36, Maitane Iturrate-Garcia17, Colleen M. Iversen43, Francesca Jaroszynska44, Jill F. Johnstone45, Rasmus Halfdan Jørgensen37, Elina Kaarlejärvi30, Elina Kaarlejärvi46, Rebecca A Klady12, Sara Kuleza45, Aino Kulonen, Laurent J. Lamarque22, Trevor C. Lantz47, Chelsea J. Little17, Chelsea J. Little48, James D. M. Speed49, Anders Michelsen37, Ann Milbau50, Jacob Nabe-Nielsen2, Sigrid Schøler Nielsen2, Josep M. Ninot28, Steven F. Oberbauer51, Johan Olofsson30, Vladimir G. Onipchenko52, Sabine B. Rumpf36, Philipp R. Semenchuk36, Philipp R. Semenchuk35, Rohan Shetti19, Laura Siegwart Collier21, Lorna E. Street1, Katharine N. Suding3, Ken D. Tape53, Andrew J. Trant21, Andrew J. Trant54, Urs A. Treier2, Jean-Pierre Tremblay55, Maxime Tremblay22, Susanna Venn56, Stef Weijers57, Tara Zamin41, Noémie Boulanger-Lapointe12, William A. Gould58, David S. Hik59, Annika Hofgaard, Ingibjörg S. Jónsdóttir60, Ingibjörg S. Jónsdóttir61, Janet C. Jorgenson62, Julia A. Klein63, Borgthor Magnusson, Craig E. Tweedie64, Philip A. Wookey65, Michael Bahn66, Benjamin Blonder67, Benjamin Blonder68, Peter M. van Bodegom24, Benjamin Bond-Lamberty69, Giandiego Campetella70, Bruno Enrico Leone Cerabolini71, F. Stuart Chapin53, William K. Cornwell72, Joseph M. Craine, Matteo Dainese, Franciska T. de Vries73, Sandra Díaz74, Brian J. Enquist75, Brian J. Enquist76, Walton A. Green77, Rubén Milla78, Ülo Niinemets79, Yusuke Onoda80, Jenny C. Ordoñez81, Wim A. Ozinga82, Wim A. Ozinga33, Josep Peñuelas40, Hendrik Poorter83, Hendrik Poorter84, Peter Poschlod85, Peter B. Reich86, Peter B. Reich87, Brody Sandel88, Brandon S. Schamp89, Serge N. Sheremetev90, Evan Weiher91 
University of Edinburgh1, Aarhus University2, University of Colorado Boulder3, Institute of Arctic and Alpine Research4, National Ecological Observatory Network5, Smithsonian Institution6, Lund University7, VU University Amsterdam8, University of Lapland9, Northern Arizona University10, Bigelow Laboratory For Ocean Sciences11, University of British Columbia12, University of Washington13, Grand Valley State University14, Swiss Federal Institute for Forest, Snow and Landscape Research15, Max Planck Society16, University of Zurich17, Université de Sherbrooke18, University of Greifswald19, University of Parma20, Memorial University of Newfoundland21, Université du Québec à Trois-Rivières22, University of Gothenburg23, Leiden University24, University of California, Riverside25, Qatar University26, Mississippi State University27, University of Barcelona28, Utrecht University29, Umeå University30, Adam Mickiewicz University in Poznań31, University of Alaska Anchorage32, Wageningen University and Research Centre33, Alaska Department of Fish and Game34, University of Tromsø35, University of Vienna36, University of Copenhagen37, Helmholtz Centre for Environmental Research - UFZ38, University of Oulu39, Spanish National Research Council40, Queen's University41, Saint Mary's University42, Oak Ridge National Laboratory43, University of Aberdeen44, University of Saskatchewan45, Vrije Universiteit Brussel46, University of Victoria47, Swiss Federal Institute of Aquatic Science and Technology48, Norwegian University of Science and Technology49, Research Institute for Nature and Forest50, Florida International University51, Moscow State University52, University of Alaska Fairbanks53, University of Waterloo54, Laval University55, Deakin University56, University of Bonn57, United States Forest Service58, Simon Fraser University59, University Centre in Svalbard60, University of Iceland61, United States Fish and Wildlife Service62, Colorado State University63, University of Texas at El Paso64, University of Stirling65, University of Innsbruck66, University of Oxford67, Rocky Mountain Biological Laboratory68, Pacific Northwest National Laboratory69, University of Camerino70, University of Insubria71, University of New South Wales72, University of Manchester73, National University of Cordoba74, Santa Fe Institute75, University of Arizona76, Harvard University77, King Juan Carlos University78, Estonian University of Life Sciences79, Kyoto University80, World Agroforestry Centre81, Radboud University Nijmegen82, Forschungszentrum Jülich83, Macquarie University84, University of Regensburg85, University of Minnesota86, University of Sydney87, Santa Clara University88, Algoma University89, Komarov Botanical Institute90, University of Wisconsin–Eau Claire91
04 Oct 2018-Nature
TL;DR: Biome-wide relationships between temperature, moisture and seven key plant functional traits across the tundra and over time show that community height increased with warming across all sites, whereas other traits lagged behind predicted rates of change.
Abstract: The tundra is warming more rapidly than any other biome on Earth, and the potential ramifications are far-reaching because of global feedback effects between vegetation and climate. A better understanding of how environmental factors shape plant structure and function is crucial for predicting the consequences of environmental change for ecosystem functioning. Here we explore the biome-wide relationships between temperature, moisture and seven key plant functional traits both across space and over three decades of warming at 117 tundra locations. Spatial temperature-trait relationships were generally strong but soil moisture had a marked influence on the strength and direction of these relationships, highlighting the potentially important influence of changes in water availability on future trait shifts in tundra plant communities. Community height increased with warming across all sites over the past three decades, but other traits lagged far behind predicted rates of change. Our findings highlight the challenge of using space-for-time substitution to predict the functional consequences of future warming and suggest that functions that are tied closely to plant height will experience the most rapid change. They also reveal the strength with which environmental factors shape biotic communities at the coldest extremes of the planet and will help to improve projections of functional changes in tundra ecosystems with climate warming.

Journal ArticleDOI
04 Jan 2018-Nature
TL;DR: It is shown, using state-of-the-art datasets, that vegetation currently stores around 450 petagrams of carbon, in the hypothetical absence of land use, which implies that trade-offs exist between conserving carbon stocks on managed land and raising the contribution of biomass to raw material and energy supply for the mitigation of climate change.
Abstract: Carbon stocks in vegetation have a key role in the climate system. However, the magnitude, patterns and uncertainties of carbon stocks and the effect of land use on the stocks remain poorly quantified. Here we show, using state-of-the-art datasets, that vegetation currently stores around 450 petagrams of carbon. In the hypothetical absence of land use, potential vegetation would store around 916 petagrams of carbon, under current climate conditions. This difference highlights the massive effect of land use on biomass stocks. Deforestation and other land-cover changes are responsible for 53-58% of the difference between current and potential biomass stocks. Land management effects (the biomass stock changes induced by land use within the same land cover) contribute 42-47%, but have been underestimated in the literature. Therefore, avoiding deforestation is necessary but not sufficient for mitigation of climate change. Our results imply that trade-offs exist between conserving carbon stocks on managed land and raising the contribution of biomass to raw material and energy supply for the mitigation of climate change. Efforts to raise biomass stocks are currently verifiable only in temperate forests, where their potential is limited. By contrast, large uncertainties hinder verification in the tropical forest, where the largest potential is located, pointing to challenges for the upcoming stocktaking exercises under the Paris agreement.

Journal ArticleDOI
01 Mar 2018-Nature
TL;DR: Xuemei Bai and colleagues call for long-term, cross-disciplinary studies to reduce carbon emissions and urban risks from global warming.
Abstract: Xuemei Bai and colleagues call for long-term, cross-disciplinary studies to reduce carbon emissions and urban risks from global warming. Xuemei Bai and colleagues call for long-term, cross-disciplinary studies to reduce carbon emissions and urban risks from global warming.

Journal ArticleDOI
01 Jan 2018
TL;DR: In this article, the authors use satellite time series data and show a widespread increase in leaf area index (a proxy for green vegetation cover), and aboveground biomass carbon, which contrasted negative trends found in the absence of anthropogenic influence as simulated by an ecosystem model.
Abstract: Afforestation and reforestation projects in the karst regions of southwest China aim to combat desertification and improve the ecological environment. However, it remains unclear at what scale conservation efforts have impacted on carbon stocks and if vegetation regrowth occurs at a large spatial scale as intended. Here we use satellite time series data and show a widespread increase in leaf area index (a proxy for green vegetation cover), and aboveground biomass carbon, which contrasted negative trends found in the absence of anthropogenic influence as simulated by an ecosystem model. In spite of drought conditions, aboveground biomass carbon increased by 9% (+0.05 Pg C y−1), mainly in areas of high conservation effort. We conclude that large scale conservation projects can contribute to a greening Earth with positive effects on carbon sequestration to mitigate climate change. At the regional scale, such ecological engineering projects may reduce risks of desertification by increasing the vegetation cover and reducing the ecosystem sensitivity to climate perturbations. Since 2000, China has attempted to vegetate huge portions of eroded landscape in its south west, bordering Vietman, Laos, and Myanmar. This study finds that this ecological engineering is combating desertification as vegetation regrows and stores carbon.

Journal ArticleDOI
25 Jul 2018-Nature
TL;DR: Tropical forests currently make a neutral contribution to the global carbon cycle, but they are likely to become a carbon source in the near future.
Abstract: Tropical forests make an approximately neutral contribution to the global carbon cycle, with intact and recovering forests taking in as much carbon as is released through deforestation and degradation. In the near future, tropical forests are likely to become a carbon source, owing to continued forest loss and the effect of climate change on the ability of the remaining forests to capture excess atmospheric carbon dioxide. This will make it harder to limit global warming to below 2 °C. Encouragingly, recent international agreements commit to halting deforestation and degradation, but a lack of fundamental data for use in monitoring and model design makes policy action difficult.

Journal ArticleDOI
TL;DR: This special feature explores the impacts of climate change and human activities on the structure and functioning of ecosystems, with emphasis on quantifying the magnitude and distribution of carbon (C) pools and C sequestration in China’s terrestrial ecosystems.
Abstract: The scale of economic growth in China during the past three decades is unprecedented in modern human history. China is now the world’s second largest economic entity, next to the United States. However, this fast economic growth puts China’s environment under increasing stresses. China can be viewed as a massive “laboratory” with complex interactions between socioeconomic and natural systems, providing an excellent opportunity to examine how environmental changes and intensive human economic activities influence natural systems. This special feature explores the impacts of climate change and human activities on the structure and functioning of ecosystems, with emphasis on quantifying the magnitude and distribution of carbon (C) pools and C sequestration in China’s terrestrial ecosystems. We also document how species diversity, species traits, and nitrogen (N) and phosphorus (P) stoichiometry mediate ecosystem C pool and vegetation production. This overview paper introduces the background and scientific significance of the research project, presents the underlying conceptual framework, and summarizes the major findings of each paper. Reducing CO2 emissions to mitigate regional and global climate change is one of the most challenging issues facing humanity (1). At present, China has the largest annual CO2 emissions in the world ( Upper graph in Fig. 1), placing it in the spotlight of efforts to manage global C emissions and design climate-change policy. It is therefore critical to improve our understanding of the C budget and its dynamics in China to mitigate climate change at both regional and global scales. Fig. 1. Evolution in total national GDP, population, and fossil fuel CO2 emissions, together with trajectory of the national policies in China between 1945 and 2015. ( Upper ) GDP, population, and CO2 emissions. The CO2 emissions data were from Oak Ridge National Laboratory (cdiac.ess-dive.lbl.gov/), and population and GDP data from the World Bank (https://data.worldbank.org/country/). ( Lower ) National … [↵][1]1To whom correspondence may be addressed. Email: jyfang{at}urban.pku.edu.cn, fangjingyun{at}ibcas.ac.cn, or terry.chapin{at}alaska.edu. [1]: #xref-corresp-1-1

Journal ArticleDOI
TL;DR: In this paper, the authors provide an overview on the current knowledge on snow, glacier, and permafrost processes, as well as their past, current, and future evolution.
Abstract: . The mountain cryosphere of mainland Europe is recognized to have important impacts on a range of environmental processes. In this paper, we provide an overview on the current knowledge on snow, glacier, and permafrost processes, as well as their past, current, and future evolution. We additionally provide an assessment of current cryosphere research in Europe and point to the different domains requiring further research. Emphasis is given to our understanding of climate–cryosphere interactions, cryosphere controls on physical and biological mountain systems, and related impacts. By the end of the century, Europe's mountain cryosphere will have changed to an extent that will impact the landscape, the hydrological regimes, the water resources, and the infrastructure. The impacts will not remain confined to the mountain area but also affect the downstream lowlands, entailing a wide range of socioeconomical consequences. European mountains will have a completely different visual appearance, in which low- and mid-range-altitude glaciers will have disappeared and even large valley glaciers will have experienced significant retreat and mass loss. Due to increased air temperatures and related shifts from solid to liquid precipitation, seasonal snow lines will be found at much higher altitudes, and the snow season will be much shorter than today. These changes in snow and ice melt will cause a shift in the timing of discharge maxima, as well as a transition of runoff regimes from glacial to nival and from nival to pluvial. This will entail significant impacts on the seasonality of high-altitude water availability, with consequences for water storage and management in reservoirs for drinking water, irrigation, and hydropower production. Whereas an upward shift of the tree line and expansion of vegetation can be expected into current periglacial areas, the disappearance of permafrost at lower altitudes and its warming at higher elevations will likely result in mass movements and process chains beyond historical experience. Future cryospheric research has the responsibility not only to foster awareness of these expected changes and to develop targeted strategies to precisely quantify their magnitude and rate of occurrence but also to help in the development of approaches to adapt to these changes and to mitigate their consequences. Major joint efforts are required in the domain of cryospheric monitoring, which will require coordination in terms of data availability and quality. In particular, we recognize the quantification of high-altitude precipitation as a key source of uncertainty in projections of future changes. Improvements in numerical modeling and a better understanding of process chains affecting high-altitude mass movements are the two further fields that – in our view – future cryospheric research should focus on.

Journal ArticleDOI
02 Feb 2018-Science
TL;DR: Environmental changes that are stressing terrestrial and marine ecosystems are described and how these stressors are being included in ESMs are discussed, initially with an emphasis on climate processes, but also show their emerging utility for VIA analyses and examine them in the context of Earth system prediction.
Abstract: BACKGROUND Earth system models (ESMs) simulate physical, chemical, and biological processes that underlie climate and are the most complex in a hierarchy of models of Earth’s interacting atmosphere–land–ocean–sea ice system. As terrestrial and marine ecosystems have been added to ESMs, the distinction between the physical basis for climate change, mitigation, and vulnerability, impacts, and adaptation (VIA) no longer necessarily holds. The same global change stresses that affect terrestrial and marine ecosystems are critical processes that determine the magnitude and trajectory of climate change, and many of the interventions that might lessen anthropogenic climate change pertain to the biosphere. Here we describe environmental changes that are stressing terrestrial and marine ecosystems. We discuss how these stressors are being included in ESMs, initially with an emphasis on climate processes, but also show their emerging utility for VIA analyses and examine them in the context of Earth system prediction. ADVANCES Terrestrial ecosystems face stresses from changing climate and atmospheric composition that alter phenology, growing season length, and community composition; these stresses enhance productivity and water-use efficiency in some regions, but also lead to mortality and increased disturbances from wildfires, insects, and extreme events in other regions. The addition of reactive nitrogen, elevated levels of tropospheric O 3 , and anthropogenic land-use and land-cover change stress ecosystems as well. The terrestrial biosphere models included in ESMs simulate the ecological impacts of these stresses and their effects on Earth system functioning. Ocean ecosystems and living marine resources face threats from ocean warming, changing large-scale circulation, increased vertical stratification, declining oxygen, and acidification, which alter nutrient supply, the light environment, and phytoplankton productivity; result in coral bleaching; and produce novel marine communities. Three-dimensional ocean models simulate the carbon cycle and associated biogeochemistry. Plankton ecosystem models both drive biogeochemistry models and characterize marine ecological dynamics. OUTLOOK The untapped potential of ESMs is to bring dispersed terrestrial and marine ecosystem research related to climate processes, VIA, and mitigation into a common framework. ESMs offer an opportunity to move beyond physical descriptors of atmospheric and oceanic states to societally relevant quantities such as habitat loss, water availability, wildfire risk, air quality, and crop, fishery, and timber yields. To do so, the science of climate prediction has to be extended to a more multifaceted Earth system prediction, including the biosphere and its resources. ESMs provide the means not just to assess the potential for future global change stresses, but also to determine the outcome of those stresses on the biosphere. Such Earth system prediction is necessary to inform sound policy that maintains a healthy biosphere and provides the food, energy, and fresh water needed for a growing global population without further exacerbating climate change. Substantial impediments that must be overcome include advancing our knowledge of biosphere-related climate processes; reducing model uncertainty; and effectively communicating among, rather than across, the disparate science communities of climate prediction, global biosphere modeling, VIA analyses, and climate change mitigation.

Journal ArticleDOI
TL;DR: In this article, the authors synthesize biological, geochemical, and physically focused CH4 climate feedback literature, bringing together the key findings of these disciplines, and discuss environment-specific feedback processes, including the microbial, physical, and geochemical interlinkages and the timescales on which they operate.
Abstract: Methane (CH4) is produced in many natural systems that are vulnerable to change under a warming climate, yet current CH4 budgets, as well as future shifts in CH4 emissions, have high uncertainties. Climate change has the potential to increase CH4 emissions from critical systems such as wetlands, marine and freshwater systems, permafrost, and methane hydrates, through shifts in temperature, hydrology, vegetation, landscape disturbance, and sea level rise. Increased CH4 emissions from these systems would in turn induce further climate change, resulting in a positive climate feedback. Here we synthesize biological, geochemical, and physically focused CH4 climate feedback literature, bringing together the key findings of these disciplines. We discuss environment-specific feedback processes, including the microbial, physical, and geochemical interlinkages and the timescales on which they operate, and present the current state of knowledge of CH4 climate feedbacks in the immediate and distant future. The important linkages between microbial activity and climate warming are discussed with the aim to better constrain the sensitivity of the CH4 cycle to future climate predictions. We determine that wetlands will form the majority of the CH4 climate feedback up to 2100. Beyond this timescale, CH4 emissions from marine and freshwater systems and permafrost environments could become more important. Significant CH4 emissions to the atmosphere from the dissociation of methane hydrates are not expected in the near future. Our key findings highlight the importance of quantifying whether CH4 consumption can counterbalance CH4 production under future climate scenarios.

Journal ArticleDOI
TL;DR: The authors reviewed the economic impacts of climate change and the policy implications of the results and concluded that climate change will likely have a limited impact on the economic well-being of the United States.
Abstract: This article reviews the economic impacts of climate change and the policy implications of the results. Current estimates indicate that climate change will likely have a limited impact on t...

Journal ArticleDOI
TL;DR: Overall, this study demonstrates that shifting plant species composition in response to climate change may have stabilized primary production in this high-elevation ecosystem, but it also caused a shift from aboveground to belowground productivity.
Abstract: The structure and function of alpine grassland ecosystems, including their extensive soil carbon stocks, are largely shaped by temperature. The Tibetan Plateau in particular has experienced significant warming over the past 50 y, and this warming trend is projected to intensify in the future. Such climate change will likely alter plant species composition and net primary production (NPP). Here we combined 32 y of observations and monitoring with a manipulative experiment of temperature and precipitation to explore the effects of changing climate on plant community structure and ecosystem function. First, long-term climate warming from 1983 to 2014, which occurred without systematic changes in precipitation, led to higher grass abundance and lower sedge abundance, but did not affect aboveground NPP. Second, an experimental warming experiment conducted over 4 y had no effects on any aspect of NPP, whereas drought manipulation (reducing precipitation by 50%), shifted NPP allocation belowground without affecting total NPP. Third, both experimental warming and drought treatments, supported by a meta-analysis at nine sites across the plateau, increased grass abundance at the expense of biomass of sedges and forbs. This shift in functional group composition led to deeper root systems, which may have enabled plant communities to acquire more water and thus stabilize ecosystem primary production even with a changing climate. Overall, our study demonstrates that shifting plant species composition in response to climate change may have stabilized primary production in this high-elevation ecosystem, but it also caused a shift from aboveground to belowground productivity.

Journal ArticleDOI
15 Nov 2018-Nature
TL;DR: The effect of urbanization on storm-induced extreme precipitation and flooding should be more explicitly included in global climate models, and this study highlights its importance when assessing the future risk of such extreme events in highly urbanized coastal areas.
Abstract: Category 4 landfalling hurricane Harvey poured more than a metre of rainfall across the heavily populated Houston area, leading to unprecedented flooding and damage. Although studies have focused on the contribution of anthropogenic climate change to this extreme rainfall event1-3, limited attention has been paid to the potential effects of urbanization on the hydrometeorology associated with hurricane Harvey. Here we find that urbanization exacerbated not only the flood response but also the storm total rainfall. Using the Weather Research and Forecast model-a numerical model for simulating weather and climate at regional scales-and statistical models, we quantify the contribution of urbanization to rainfall and flooding. Overall, we find that the probability of such extreme flood events across the studied basins increased on average by about 21 times in the period 25-30 August 2017 because of urbanization. The effect of urbanization on storm-induced extreme precipitation and flooding should be more explicitly included in global climate models, and this study highlights its importance when assessing the future risk of such extreme events in highly urbanized coastal areas.

Journal ArticleDOI
Anny Cazenave, Benoit Meyssignac, Michael Ablain, Magdalena Balmaseda1, Jonathan L. Bamber2, Valentina R. Barletta3, Brian D. Beckley4, Jérôme Benveniste5, Etienne Berthier, Alejandro Blazquez, Timothy P. Boyer6, Denise Cáceres7, Don P. Chambers8, Nicolas Champollion9, Ben Chao10, Jianli Chen11, Lijing Cheng12, John A. Church13, Stephen Chuter2, J. Graham Cogley14, Soenke Dangendorf15, Damien Desbruyères16, Petra Döll7, Catia M. Domingues17, Ulrike Falk9, James S. Famiglietti18, Luciana Fenoglio-Marc19, René Forsberg3, Gaia Galassi20, Alex S. Gardner18, Andreas Groh21, Benjamin D. Hamlington22, Anna E. Hogg23, Martin Horwath21, Vincent Humphrey24, Laurent Husson25, Masayoshi Ishii, A. Jaeggi26, Svetlana Jevrejeva27, Gregory C. Johnson6, Nicolas Kolodziejczyk, Jürgen Kusche19, Kurt Lambeck28, Felix W. Landerer18, P. W. Leclercq29, Benoit Legresy17, Eric Leuliette6, William Llovel, Laurent Longuevergne30, Bryant D. Loomis4, Scott B. Luthcke4, Marta Marcos31, Ben Marzeion9, Christopher J. Merchant32, Mark A. Merrifield33, Glenn A. Milne34, Gary T. Mitchum8, Yara Mohajerani35, Maeva Monier, Didier Monselesan17, Steve Nerem36, Hindumathi Palanisamy, Frank Paul37, Begoña Pérez, Christopher G. Piecuch38, Rui M. Ponte, Sarah G. Purkey33, John T. Reager18, Roelof Rietbroek19, Eric Rignot35, Riccardo Riva39, Dean Roemmich33, Louise Sandberg Sørensen3, Ingo Sasgen40, E.J.O. Schram39, Sonia I. Seneviratne24, C. K. Shum41, Giorgio Spada20, Detlef Stammer42, Roderic van de Wal43, Isabella Velicogna44, Karina von Schuckmann, Yoshihide Wada43, Yiguo Wang45, Christopher Watson46, David N. Wiese18, Susan Wijffels17, Richard M. Westaway2, Guy Wöppelmann47, Bert Wouters43 
TL;DR: In this paper, the authors present estimates of the altimetry-based global mean sea level (average variance of 3.1 +/- 0.3 mm/yr and acceleration of 0.1 mm/r2 over 1993-present), as well as of the different components of the sea level budget over 2005-present, using GRACE-based ocean mass estimates.
Abstract: Global mean sea level is an integral of changes occurring in the climate system in response to unforced climate variability as well as natural and anthropogenic forcing factors. Its temporal evolution allows detecting changes (e.g., acceleration) in one or more components. Study of the sea level budget provides constraints on missing or poorly known contributions, such as the unsurveyed deep ocean or the still uncertain land water component. In the context of the World Climate Research Programme Grand Challenge entitled “Regional Sea Level and Coastal Impacts”, an international effort involving the sea level community worldwide has been recently initiated with the objective of assessing the various data sets used to estimate components of the sea level budget during the altimetry era (1993 to present). These data sets are based on the combination of a broad range of space-based and in situ observations, model estimates and algorithms. Evaluating their quality, quantifying uncertainties and identifying sources of discrepancies between component estimates is extremely useful for various applications in climate research. This effort involves several tens of scientists from about fifty research teams/institutions worldwide (www.wcrp-climate.org/grand-challenges/gc-sea- level). The results presented in this paper are a synthesis of the first assessment performed during 2017-2018. We present estimates of the altimetry-based global mean sea level (average rate of 3.1 +/- 0.3 mm/yr and acceleration of 0.1 mm/yr2 over 1993-present), as well as of the different components of the sea level budget (http://doi.org/10.17882/54854). We further examine closure of the sea level budget, comparing the observed global mean sea level with the sum of components. Ocean thermal expansion, glaciers, Greenland and Antarctica contribute by 42%, 21%, 15% and 8% to the global mean sea level over the 1993-present. We also study the sea level budget over 2005-present, using GRACE-based ocean mass estimates instead of sum of individual mass components. Results show closure of the sea level budget within 0.3 mm/yr. Substantial uncertainty remains for the land water storage component, as shown in examining individual mass contributions to sea level.

Journal ArticleDOI
TL;DR: In this paper, the state of local planning for climate change by collecting and analysing information about local climate mitigation and adaptation plans across 885 urban areas of the EU-28 was reported.