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Earth System Models are not capturing present‐day tropical forest carbon dynamics

Koch, A; Hubau, W; Lewis, SL; (2021) Earth System Models are not capturing present‐day tropical forest carbon dynamics. Earth's Future , 9 (5) , Article e2020EF001874. 10.1029/2020ef001874. Green open access

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Abstract

Tropical forests play a key role in absorbing carbon from the atmosphere into the land surface. Recent analyses of long‐term (1985‐2014) forest inventory plots across the tropics show that structurally intact tropical forest are a large carbon sink, but that this sink has saturated and is projected to be in long‐term decline. Here we compare these results with estimates from the two latest generations of Earth System Models, CMIP5 (19 models) and CMIP6 (17 models). While CMIP5 and CMIP6 are of similar skill, they do not reproduce the observed 1985‐2014 carbon dynamics. The ‘natural’ pan‐tropical carbon sink from inventory data is 0.99 Pg C yr‐1 (95% CI 0.7‐1.3, n=614) between 2000‐2010, the best sampled decade, double the CMIP6 multimodel‐mean of 0.45 Pg C yr‐1 (95% CI 0.35‐0.55). The observed saturating and declining sink is not captured by the models, which show modest increases in sink strength. The future (2015‐2040) ‘natural’ pan‐tropical sink from a statistical model driven by extrapolating past trends of its putative environmental drivers decreases by 0.23 Pg C per decade (95% CI 0.09‐0.39) until the 2030s, while the CMIP6 multimodel‐mean under the climate change scenario closest to the statistical model project an increasing carbon sink (0.54 Pg C per decade; 95% CI 0.25‐0.67). CMIP multimodel‐means reproduce the response of carbon gains from tree growth to environmental drivers, but the modelling of carbon losses from tree mortality does not correspond well to the inventory data. The model‐observation differences primarily result from the treatment of mortality in models.

Type: Article
Title: Earth System Models are not capturing present‐day tropical forest carbon dynamics
Open access status: An open access version is available from UCL Discovery
DOI: 10.1029/2020ef001874
Publisher version: https://doi.org/10.1029/2020ef001874
Language: English
Additional information: © 2021. The Authors. Earth's Future published by Wiley Periodicals LLC on behalf of American Geophysical Union. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Keywords: Earth System Models, tropical forest, carbon cycle, climate change, ecosystem dynamics
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL SLASH
UCL > Provost and Vice Provost Offices > UCL SLASH > Faculty of S&HS
UCL > Provost and Vice Provost Offices > UCL SLASH > Faculty of S&HS > Dept of Geography
URI: https://discovery.ucl.ac.uk/id/eprint/10127581
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