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Effects of Irrigation on Global Climate During the 20th CenturyVarious studies have documented the effects of modern ]day irrigation on regional and global climate, but none, to date, have considered the time ]varying impact of steadily increasing irrigation rates on climate during the 20th century. We investigate the impacts of observed irrigation changes over this century with two ensemble simulations using an atmosphere general circulation model. Both ensembles are forced with transient climate forcings and observed sea surface temperatures from 1902 to 2000; one ensemble includes irrigation specified by a time ]varying data set of irrigation water withdrawals. Early in the century, irrigation is primarily localized over southern and eastern Asia, leading to significant cooling in boreal summer (June.August) over these regions. This cooling spreads and intensifies by century fs end, following the rapid expansion of irrigation over North America, Europe, and Asia. Irrigation also leads to boreal winter (December.February) warming over parts of North America and Asia in the latter part of the century, due to enhanced downward longwave fluxes from increased near ]surface humidity. Precipitation increases occur primarily downwind of the major irrigation areas, although precipitation in parts of India decreases due to a weaker summer monsoon. Irrigation begins to significantly reduce temperatures and temperature trends during boreal summer over the Northern Hemisphere midlatitudes and tropics beginning around 1950; significant increases in precipitation occur in these same latitude bands. These trends reveal the varying importance of irrigation ]climate interactions and suggest that future climate studies should account for irrigation, especially in regions with unsustainable irrigation resources.
Document ID
20120009283
Acquisition Source
Goddard Space Flight Center
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Puma, M. J.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Cook, B. I.
(NASA Goddard Space Flight Center Greenbelt, MD, United States)
Date Acquired
August 25, 2013
Publication Date
August 28, 2010
Publication Information
Publication: Journal of Geophysical Research - Atmospheres
Volume: 115
ISSN: 0148-0227
Subject Category
Meteorology And Climatology
Report/Patent Number
GSFC.JA.5997.2012
Funding Number(s)
CONTRACT_GRANT: NNX08AJ75A
Distribution Limits
Public
Copyright
Other

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