Climate mitigation from vegetation biophysical feedbacks during the past three decades

Zhenzhong Zeng (1) , Shilong Piao (1, 2) , Laurent Z. X. Li (3) , Liming Zhou (4) , Philippe Ciais (5, 6) , Tao Wang (2) , Yue Li (1) , Xu Lian (1) , Eric F. Wood (7) , Pierre Friedlingstein (8) , Jiafu Mao (9) , Lyndon D. Estes (7, 10) , Ranga B. Myneni (11) , Shushi Peng (1) , Xiaoying Shi (9) , Sonia I. Seneviratne (12) , Yingping Wang (13)

1 Sino-French Institute for Earth System Science, College of Urban and Environmental Sciences
2 CAS Center for Excellence in Tibetan Plateau Earth Sciences
3 LMD - Laboratoire de Météorologie Dynamique (UMR 8539)
4 DAES - Department of Atmospheric and Environmental Sciences [Albany]
5 LSCE - Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette]
6 ICOS-ATC - ICOS-ATC
7 Department of Civil and Environmental Engineering [Princeton]
8 EMPS - College of Engineering, Mathematics and Physical Sciences [Exeter]
9 Environmental Sciences Division [Oak Ridge]
10 Princeton's Woodrow Wilson School of Public and International Affairs
11 EEOS - Department of Environmental, Earth and Ocean Sciences [Boston]
12 IAC - Institute for Atmospheric and Climate Science [Zürich]
13 CSIRO Marine and Atmospheric Research [Aspendale]

The surface air temperature response to vegetation changes has been studied for the extreme case of land-cover change; yet, it has never been quantified for the slow but persistent increase in leaf area index (LAI) observed over the past 30 years (Earth greening). Here we isolate the fingerprint of increasing LAI on surface air temperature using a coupled land–atmosphere global climate model prescribed with satellite LAI observations. We find that the global greening has slowed down the rise in global land-surface air temperature by 0.09 ± 0.02 °C since 1982. This net cooling effect is the sum of cooling from increased evapotranspiration (70%), changed atmospheric circulation (44%), decreased shortwave transmissivity (21%), and warming from increased longwave air emissivity (−29%) and decreased albedo (−6%). The global cooling originated from the regions where LAI has increased, including boreal Eurasia, Europe, India, northwest Amazonia, and the Sahel. Increasing LAI did not, however, significantly change surface air temperature in eastern North America and East Asia, where the effects of large-scale atmospheric circulation changes mask local vegetation feedbacks. Overall, the sum of biophysical feedbacks related to the greening of the Earth mitigated 12% of global land-surface warming for the past 30 years.

Domaines: Climatologie

Zhenzhong Zeng, Shilong Piao, Laurent Z. X. Li, Liming Zhou, Philippe Ciais, et al.. Climate mitigation from vegetation biophysical feedbacks during the past three decades. Nature Climate Change, 2017, 7 (6), pp.432-436. ⟨10.1038/NCLIMATE3299⟩. ⟨cea-02134642⟩