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The dominant role of semi-arid ecosystems in the trend and variability of the land CO2 sink

Anders Ahlström, Michael R. Raupach, Guy Schurgers, Benjamin Smith, Almut Arneth, Martin Jung, Markus Reichstein, Josep G. Canadell, Pierre Friedlingstein, Atul K. Jain, Etsushi Kato, Benjamin Poulter, Stephen Sitch, Benjamin D. Stocker, Nicolas Viovy, Ying Ping Wang, Andy Wiltshire, Sönke Zaehle, Ning Zeng

Science, published: 22 May 2015
DOI: 10.1126/science.aaa1668

Paper Abstract

The growth rate of atmospheric carbon dioxide (CO2) concentrations since industrialization is characterized by large interannual variability, mostly resulting from variability in CO2 uptake by terrestrial ecosystems. However, the contributions of regional ecosystems to that variability are not well known. Using an ensemble of ecosystem and land-surface models and an empirical observation-based product of global gross primary production, we show that the mean sink, trend, and interannual variability in CO2 uptake by terrestrial ecosystems are dominated by distinct biogeographic regions.Whereas the sink strength is dominated by highly productive lands (mainly tropical forests), the trend and interannual variability of the sink are dominated by semi-arid ecosystems whose carbon balance is strongly associated with circulation-driven variations in both precipitation and temperature.

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Illustrative Photos (available free if credited as specified)
Semi-arid region of Western Australia Semi-arid region of Western Australia  
Semi-arid region of Western Australia.
Photo credit: Luciana Porfirio
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Semi-arid region of Western Australia.
Credit: Luciana Porfirio
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Semi-arid region of Western Australia Semi-arid region of Central Australia
Semi-arid region of Western Australia.
Photo credit: Luciana Porfirio
(994 x 1302, jpg 744 kb)
Semi-arid region of Central Australia.
Photo credit: Luciana Porfirio
(2590 x 1215, jpg 724 kb)