Oct 10, 2010

Recent decline in the global land evapotranspiration trend due to limited moisture supply

by
Martin Jung, Markus Reichstein, Philippe Ciais, Sonia I. Seneviratne, Justin Sheffield, Michael L. Goulden, Gordon Bonan, Alessandro Cescatti, Jiquan Chen, Richard de Jeu, A. Johannes Dolman, Werner Eugster, Dieter Gerten, Damiano Gianelle et al
,
Nature
  • States more than half of the solar energy absorbed by land surfaces is currently used to evaporate water
  • States climate change is expected to intensify the hydrological cycle and to alter evapotranspiration, with implications for ecosystem services and feedback to regional and global climate
  • Provides a data-driven estimate of global land evapotranspiration from 1982 to 2008, compiled using a global monitoring network, meteorological and remote-sensing observations, and a machine-learning algorithm
  • Results suggest that global annual evapotranspiration increased on average by 7.1 ± 1.0 millimetres per year per decade from 1982 to 1997
  • Finds that after 1997, coincident with the major El Niño event in 1998, the global evapotranspiration increase seems to have ceased until 2008
  • Finds the change was driven primarily by moisture limitation in the Southern Hemisphere, particularly Africa and Australia
  • Analyzes microwave satellite observations, which indicate that soil moisture decreased from 1998 to 2008
  • Finds increasing soil-moisture limitations on evapotranspiration largely explain the recent decline of the global land-evapotranspiration trend
  • States that whether the changing behaviour of evapotranspiration is representative of natural climate variability or reflects a more permanent reorganization of the land water cycle is a key question for earth system science