Title: Impact of Earth Greening on the Terrestrial Water Cycle

Abstract

Leaf area index (LAI) is increasing throughout the globe, implying Earth greening. Global modeling studies support this contention, yet satellite observations and model simulations have never been directly compared. Here, for the first time, a coupled land–climate model was used to quantify the potential impact of the satellite-observed Earth greening over the past 30 years on the terrestrial water cycle. The global LAI enhancement of 8% between the early 1980s and the early 2010s is modeled to have caused increases of 12.0 ± 2.4 mm yr^–1 in evapotranspiration and 12.1 ± 2.7 mm yr^–1 in precipitation—about 55% ± 25% and 28% ± 6% of the observed increases in land evapotranspiration and precipitation, respectively. In wet regions, the greening did not significantly decrease runoff and soil moisture because it intensified moisture recycling through a coincident increase of evapotranspiration and precipitation. But in dry regions, including the Sahel, west Asia, northern India, the western United States, and the Mediterranean coast, the greening was modeled to significantly decrease soil moisture through its coupling with the atmospheric water cycle. This modeled soil moisture response, however, might have biases resulting from the precipitation biases in the model. For example, the model dry bias might havemore » underestimated the soil moisture response in the observed dry area (e.g., the Sahel and northern India) given that the modeled soil moisture is near the wilting point. Thus, an accurate representation of precipitation and its feedbacks in Earth system models is essential for simulations and predictions of how soil moisture responds to LAI changes, and therefore how the terrestrial water cycle responds to climate change.« less

Authors:

Zeng, Zhenzhong ^[1]; Piao, Shilong ^[2]; Li, Laurent Z. X. ^[3]; Wang, Tao ^[4]; Ciais, Philippe ^[5]; Lian, Xu ^[1]; Yang, Yuting ^[6]; Mao, Jiafu ^[7]; Shi, Xiaoying ^[7]; Myneni, Ranga B. ^[8]

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+ Show Author Affiliations

1. Sino-French Institute for Earth System Science, College of Urban and Environmental Sciences, Peking University, Beijing, China
2. Sino-French Institute for Earth System Science, College of Urban and Environmental Sciences, Peking University, Beijing, China, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing, China
3. Laboratoire de Météorologie Dynamique, CNRS, Sorbonne Université, UPMC Université Paris 06, Paris, France
4. Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing, China
5. Sino-French Institute for Earth System Science, College of Urban and Environmental Sciences, Peking University, Beijing, China, Laboratoire des Sciences du Climat et de l’Environnement, CEA-CNRS-UVSQ, Gif-sur-Yvette, France
6. CSIRO Land and Water, Black Mountain, Canberra, Australian Capital Territory, Australia
7. Environmental Sciences Division and Climate Change Science Institute, Oak Ridge National Laboratory, Oak Ridge, Tennessee
8. Department of Earth and Environment, Boston University, Boston, Massachusetts

Publication Date:

Sun Apr 01 00:00:00 EDT 2018

Research Org.:

Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Biological and Environmental Research (BER)

OSTI Identifier:

1423728

Alternate Identifier(s):

OSTI ID: 1515690

Grant/Contract Number:  

RUBISCO SFA; AC05-00OR22725

Resource Type:

Published Article

Journal Name:

Journal of Climate

Additional Journal Information:

Journal Name: Journal of Climate Journal Volume: 31 Journal Issue: 7; Journal ID: ISSN 0894-8755

Publisher:

American Meteorological Society

Country of Publication:

United States

Language:

English

Subject:

54 ENVIRONMENTAL SCIENCES; Atmosphere-land interaction; Vegetation-atmosphere interactions; Vegetation; Evapotranspiration; Feedback