title: Vegetation Greening and Climate Change Promote Multidecadal Rises of Global Land Evapotranspiration.
abstract: Recent studies showed that anomalous dry conditions and limited moisture supply roughly between 1998 and 2008, especially in the Southern Hemisphere, led to reduced vegetation productivity and ceased growth in land evapotranspiration (ET). However, natural variability of Earth's climate system can degrade capabilities for identifying climate trends. Here we produced a long-term (1982-2013) remote sensing based land ET record and investigated multidecadal changes in global ET and underlying causes. The ET record shows a significant upward global trend of 0.88 mm yr(-2) (P < 0.001) over the 32-year period, mainly driven by vegetation greening (0.018% per year; P < 0.001) and rising atmosphere moisture demand (0.75 mm yr(-2); P = 0.016). Our results indicate that reduced ET growth between 1998 and 2008 was an episodic phenomenon, with subsequent recovery of the ET growth rate after 2008. Terrestrial precipitation also shows a positive trend of 0.66 mm yr(-2) (P = 0.08) over the same period consistent with expected water cycle intensification, but this trend is lower than coincident increases in evaporative demand and ET, implying a possibility of cumulative water supply constraint to ET. Continuation of these trends will likely exacerbate regional drought-induced disturbances, especially during regional dry climate phases associated with strong El Niño events.
authors.affiliation: Cooperative Institute for Mesosacle Meteorological Studies, The University of Oklahoma, 120 David L. Boren Blvd., Norman, OK 73072, USA.|Hydrometeorology &Remote Sensing (HyDROS) Laboratory and School of Civil Engineering and Environmental Sciences, University of Oklahoma, Norman, OK.|State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering, Hohai University, 1 Xikang Road, Nanjing, Jiangsu Province, 210098, China.
authors.forename: Ke
authors.initials: K
authors.lastname: Zhang
authors.affiliation: Numerical Terradynamic Simulation Group, The University of Montana, 32 Campus Drive #1224, Missoula, MT 59812-1224, USA.
authors.forename: John S
authors.initials: JS
authors.lastname: Kimball
authors.affiliation: NASA Ames Research Center, Moffett Field, CA, USA.
authors.forename: Ramakrishna R
authors.initials: RR
authors.lastname: Nemani
authors.affiliation: Numerical Terradynamic Simulation Group, The University of Montana, 32 Campus Drive #1224, Missoula, MT 59812-1224, USA.
authors.forename: Steven W
authors.initials: SW
authors.lastname: Running
authors.affiliation: Hydrometeorology &Remote Sensing (HyDROS) Laboratory and School of Civil Engineering and Environmental Sciences, University of Oklahoma, Norman, OK.|Department of Hydraulic Engineering, Tsinghua University, Beijing, China.
authors.forename: Yang
authors.initials: Y
authors.lastname: Hong
authors.affiliation: NOAA/National Severe Storms Laboratory, Norman, Oklahoma 73072, USA.
authors.forename: Jonathan J
authors.initials: JJ
authors.lastname: Gourley
authors.affiliation: State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering, Hohai University, 1 Xikang Road, Nanjing, Jiangsu Province, 210098, China.
authors.forename: Zhongbo
authors.initials: Z
authors.lastname: Yu
mesh_terms: D000465:Algorithms; D001272:Atmosphere; D002245:Carbon Dioxide / Q000378:metabolism; D057231:Climate Change; D018556:Crops, Agricultural / Q000254:growth & development; D055864:Droughts; D059000:El Nino-Southern Oscillation; D014867:Water / Q000737:chemistry / Q000378:metabolism
chemical_list: D014867:Water; D002245:Carbon Dioxide