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Asynchronous carbon sink saturation in African and Amazonian tropical forests 期刊论文
NATURE, 2020, 579 (7797) : 80-+
作者:  Wannes Hubau;  Simon L. Lewis;  Oliver L. Phillips;  Kofi Affum-Baffoe;  Hans Beeckman;  Aida Cuní;  -Sanchez;  Armandu K. Daniels;  Corneille E. N. Ewango;  Sophie Fauset;  Jacques M. Mukinzi;  Douglas Sheil;  Bonaventure Sonké;  Martin J. P. Sullivan;  Terry C. H. Sunderland;  Hermann Taedoumg;  Sean C. Thomas;  Lee J. T. White;  Katharine A. Abernethy;  Stephen Adu-Bredu;  Christian A. Amani;  Timothy R. Baker;  Lindsay F. Banin;  Fidè;  le Baya;  Serge K. Begne;  Amy C. Bennett;  Fabrice Benedet;  Robert Bitariho;  Yannick E. Bocko;  Pascal Boeckx;  Patrick Boundja;  Roel J. W. Brienen;  Terry Brncic;  Eric Chezeaux;  George B. Chuyong;  Connie J. Clark;  Murray Collins;  James A. Comiskey;  David A. Coomes;  Greta C. Dargie;  Thales de Haulleville;  Marie Noel Djuikouo Kamdem;  Jean-Louis Doucet;  Adriane Esquivel-Muelbert;  Ted R. Feldpausch;  Alusine Fofanah;  Ernest G. Foli;  Martin Gilpin;  Emanuel Gloor;  Christelle Gonmadje;  Sylvie Gourlet-Fleury;  Jefferson S. Hall;  Alan C. Hamilton;  David J. Harris;  Terese B. Hart;  Mireille B. N. Hockemba;  Annette Hladik;  Suspense A. Ifo;  Kathryn J. Jeffery;  Tommaso Jucker;  Emmanuel Kasongo Yakusu;  Elizabeth Kearsley;  David Kenfack;  Alexander Koch;  Miguel E. Leal;  Aurora Levesley;  Jeremy A. Lindsell;  Janvier Lisingo;  Gabriela Lopez-Gonzalez;  Jon C. Lovett;  Jean-Remy Makana;  Yadvinder Malhi;  Andrew R. Marshall;  Jim Martin;  Emanuel H. Martin;  Faustin M. Mbayu;  Vincent P. Medjibe;  Vianet Mihindou;  Edward T. A. Mitchard;  Sam Moore;  Pantaleo K. T. Munishi;  Natacha Nssi Bengone;  Lucas Ojo;  Fidè;  le Evouna Ondo;  Kelvin S.-H. Peh;  Georgia C. Pickavance;  Axel Dalberg Poulsen;  John R. Poulsen;  Lan Qie;  Jan Reitsma;  Francesco Rovero;  Michael D. Swaine;  Joey Talbot;  James Taplin;  David M. Taylor;  Duncan W. Thomas;  Benjamin Toirambe;  John Tshibamba Mukendi;  Darlington Tuagben;  Peter M. Umunay;  Geertje M. F. van der Heijden;  Hans Verbeeck;  Jason Vleminckx;  Simon Willcock;  Hannsjö;  rg Wö;  ll;  John T. Woods;  Lise Zemagho
收藏  |  浏览/下载：23/0  |  提交时间：2020/05/13

Structurally intact tropical forests sequestered about half of the global terrestrial carbon uptake over the 1990s and early 2000s, removing about 15 per cent of anthropogenic carbon dioxide emissions(1-3). Climate-driven vegetation models typically predict that this tropical forest '  carbon sink'  will continue for decades(4,5). Here we assess trends in the carbon sink using 244 structurally intact African tropical forests spanning 11 countries, compare them with 321 published plots from Amazonia and investigate the underlying drivers of the trends. The carbon sink in live aboveground biomass in intact African tropical forests has been stable for the three decades to 2015, at 0.66 tonnes of carbon per hectare per year (95 per cent confidence interval 0.53-0.79), in contrast to the long-term decline in Amazonian forests(6). Therefore the carbon sink responses of Earth'  s two largest expanses of tropical forest have diverged. The difference is largely driven by carbon losses from tree mortality, with no detectable multi-decadal trend in Africa and a long-term increase in Amazonia. Both continents show increasing tree growth, consistent with the expected net effect of rising atmospheric carbon dioxide and air temperature(7-9). Despite the past stability of the African carbon sink, our most intensively monitored plots suggest a post-2010 increase in carbon losses, delayed compared to Amazonia, indicating asynchronous carbon sink saturation on the two continents. A statistical model including carbon dioxide, temperature, drought and forest dynamics accounts for the observed trends and indicates a long-term future decline in the African sink, whereas the Amazonian sink continues to weaken rapidly. Overall, the uptake of carbon into Earth'  s intact tropical forests peaked in the 1990s. Given that the global terrestrial carbon sink is increasing in size, independent observations indicating greater recent carbon uptake into the Northern Hemisphere landmass(10) reinforce our conclusion that the intact tropical forest carbon sink has already peaked. This saturation and ongoing decline of the tropical forest carbon sink has consequences for policies intended to stabilize Earth'  s climate.


  
Mass balance of the Greenland Ice Sheet from 1992 to 2018 期刊论文
NATURE, 2020, 579 (7798) : 233-+
作者:  Scudellari, Megan
收藏  |  浏览/下载：11/0  |  提交时间：2020/04/16

The Greenland Ice Sheet has been a major contributor to global sea-level rise in recent decades(1,2), and it is expected to continue to be so(3). Although increases in glacier flow(4-6) and surface melting(7-9) have been driven by oceanic(10-12) and atmospheric(13,14) warming, the magnitude and trajectory of the ice sheet'  s mass imbalance remain uncertain. Here we compare and combine 26 individual satellite measurements of changes in the ice sheet'  s volume, flow and gravitational potential to produce a reconciled estimate of its mass balance. The ice sheet was close to a state of balance in the 1990s, but annual losses have risen since then, peaking at 345 +/- 66 billion tonnes per year in 2011. In all, Greenland lost 3,902 +/- 342 billion tonnes of ice between 1992 and 2018, causing the mean sea level to rise by 10.8 +/- 0.9 millimetres. Using three regional climate models, we show that the reduced surface mass balance has driven 1,964 +/- 565 billion tonnes (50.3 per cent) of the ice loss owing to increased meltwater runoff. The remaining 1,938 +/- 541 billion tonnes (49.7 per cent) of ice loss was due to increased glacier dynamical imbalance, which rose from 46 +/- 37 billion tonnes per year in the 1990s to 87 +/- 25 billion tonnes per year since then. The total rate of ice loss slowed to 222 +/- 30 billion tonnes per year between 2013 and 2017, on average, as atmospheric circulation favoured cooler conditions(15) and ocean temperatures fell at the terminus of Jakobshavn Isbr AE(16). Cumulative ice losses from Greenland as a whole have been close to the rates predicted by the Intergovernmental Panel on Climate Change for their high-end climate warming scenario(17), which forecast an additional 70 to 130 millimetres of global sea-level rise by 2100 compared with their central estimate.