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SUMMARY:Irrigation in the climate system: transient and equilibrium respon
 ses
DTSTART:20110228T161500
DTSTAMP:20260510T101024Z
UID:f7f99641eda778babcd8153580a1c2d161b676233057988716a93127
CATEGORIES:Conferences - Seminars
DESCRIPTION:Dr Ben COOK\; NASA Goddard Institute for Space Studies New Yor
 k\, USA\nVarious studies have documented the effects of modern-day irrigat
 ion on regional and global climate\, but few have considered 1) the time-v
 arying impact of steadily increasing irrigation rates on climate during th
 e twentieth century or 2) how the effect of irrigation on surface climate 
 will change with increased greenhouse gas (GHG) forcing. To address these 
 questions\, we use spatially explicit estimates of modern and historical i
 rrigation\, in combination with historical and increased GHG forcings\, to
  force several transient and equilibrium runs with an atmosphere general c
 irculation model. In our historical simulations\, irrigation early in the 
 twentieth century is primarily localized over southern and eastern Asia\, 
 leading to significant cooling in boreal summer (June-August) over these r
 egions. This cooling spreads and intensifies by century's end\, following 
 the rapid expansion of irrigation over North America\, Europe\, and Asia. 
 Irrigation also leads to boreal winter (December-February) warming over pa
 rts of North America and Asia in the latter part of the century\, through 
 enhanced downward longwave fluxes from increased near-surface humidity. Pr
 ecipitation increases occur primarily downwind of the major irrigation are
 as\, although precipitation in parts of India decreases due to a weaker su
 mmer monsoon. Irrigation begins to significantly reduce temperatures and t
 emperature trends during boreal summer over the Northern Hemisphere midlat
 itudes and tropics beginning around 1950\; significant increases in precip
 itation occur in these same latitude bands. For the modern equilibrium sce
 nario\, the cooling is largest over North America\, India\, the Middle Eas
 t\, and East Asia. Under increased GHG forcing\, this cooling effect large
 ly disappears over North America\, remains relatively unchanged over India
 \, and intensifies over parts of China and the Middle East. For North Amer
 ica\, irrigation significantly increases precipitation under modern GHG fo
 rcing\; this precipitation enhancement largely disappears under A1B forcin
 g\, reducing total latent heat fluxes and the overall irrigation cooling e
 ffect. 
LOCATION:GR B3 30
STATUS:CONFIRMED
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