labs_title

Disentangling climatic and anthropogenic controls on global terrestrial evapotranspiration trends

J. Mao, W. Fu, X. Shi, D.M. Ricciuto, J.B. Fisher, R.E. Dickinson, Y. Wei, W. Shem, S. Piao, K. Wang, C.R. Schwalm, H. Tian, M. Mu, A. Arain, P. Ciais, R. Cook, Y. Dai, D. Hayes, F.M. Hoffman, M. Huang, S. Huang, D.N. Huntzinger, A. Ito, A. Jain, A.W. King, H. Lei, C. Lu, A.M. Michalak, N. Parazoo, C. Peng, S. Peng, B. Poulter, K. Schaefer, E. Jafarov, P.E. Thornton, W. Wang, N. Zeng, Z. Zeng, F. Zhao, Q. Zhu and Z. Zhu

Evapotranspiration, the sum of water evaporation and plant transpiration of water, is a key component of the global water cycle. This paper examines the impacts of changing climate, atmospheric concentrations of carbon dioxide, nitrogen deposition and land use / land cover on global evapotranspiration over the last three decades, through the use of an ensemble of process-based models from the MsTMIP effort.


Figure: Spatial distribution of the linear trends in ET median values (mm yr−2) for (a) ET_DIA, (b) ET_ALL, (c) ET_CLI, (d) ET_OTH, (e) CO2 (ET_CO2), (f) NDE (ET_NDE), and (g) LUC (ET_LUC) from 1982 to 2010. The stippled areas represent the trends are statistically significant (P < 0.05), and the insets show the frequency distribution of the corresponding change.

Abstract

We examined natural and anthropogenic controls on terrestrial evapotranspiration (ET) changes from 1982 to 2010 using multiple estimates from remote sensing-based datasets and process-oriented land surface models. A significant increasing trend of ET in each hemisphere was consistently revealed by observationally-constrained data and multi-model ensembles that considered historic natural and anthropogenic drivers. The climate impacts were simulated to determine the spatiotemporal variations in ET. Globally, rising CO2 ranked second in these models after the predominant climatic influences, and yielded decreasing trends in canopy transpiration and ET, especially for tropical forests and high-latitude shrub land. Increasing nitrogen deposition slightly amplified global ET via enhanced plant growth. Land-use-induced ET responses, albeit with substantial uncertainties across the factorial analysis, were minor globally, but pronounced locally, particularly over regions with intensive land-cover changes. Our study highlights the importance of employing multi-stream ET and ET-component estimates to quantify the strengthening anthropogenic fingerprint in the global hydrologic cycle.

Mao, J., W. Fu, X. Shi, D.M. Ricciuto, J.B. Fisher, R.E. Dickinson, Y. Wei, W. Shem, S. Piao, K. Wang, C.R. Schwalm, H. Tian, M. Mu, A. Arain, P. Ciais, R. Cook, Y. Dai, D. Hayes, F.M. Hoffman, M. Huang, S. Huang, D.N. Huntzinger, A. Ito, A. Jain, A.W. King, H. Lei, C. Lu, A.M. Michalak, N. Parazoo, C. Peng, S. Peng, B. Poulter, K. Schaefer, E. Jafarov, P.E. Thornton, W. Wang, N. Zeng, Z. Zeng, F. Zhao, Q. Zhu, Z. Zhu (2015) "Disentangling climatic and anthropogenic controls on global terrestrial evapotranspiration trends", Environmental Research Letters, 10(9):094008, doi:10.1088/1748-9326/10/9/094008.