A new study in the recent issue of the Proceedings of the National Academy of Sciences (PNAS) has shown that expansive irrigation will not be able to cool the globe in the future.
Washington, Aug 15 : A new study in the recent issue of the Proceedings of the National Academy of Sciences (PNAS) has shown that expansive irrigation will not be able to cool the globe in the future.
Scientists from the Lawrence Livermore National Laboratory (LLNL) found that irrigation-induced cooling in agricultural areas had slowed down remarkably in recent years.
"Globally, we derive 40 percent of our food from irrigated regions, so we'd like to be able to model future climate changes in these regions. This is not a model result, but something very clearly evident in the data. We also looked at other major irrigated regions in the world, and saw a very similar pattern," said Celine Bonfils, lead author of the study.
The team first studied the net impact of widespread irrigation on local and regional climate in California, the top irrigating state in the United States (3.3 million hectares).
In highly irrigated regions of the San Joaquin Valley, daytime temperatures relative to low irrigated areas have cooled by 1.8 degrees - 3.2 degrees C since the introduction of irrigation practice in 1887.
"In comparison, there was no clear effect of irrigation on temperatures over the 1980-2000 period when there was no net growth of irrigation," said co-author David Lobell, also from LLNL.
The study further showed that irrigation expansion could not explain the rapid summer nighttime warming, well observed in Central California since 1915.
"Our results show that the expansion of irrigation has almost no effect on minimum temperatures and that irrigation cannot be blamed for this rapid warming. An increase in greenhouse gases and urbanization would best explain this trend, which exceeds what is possible from natural climate variability alone," Lobell added.
ANI