Guest essay by Eric Worrall

According to a Swiss study, the Tropics are not warming as rapidly as expected because of large scale agricultural irrigation.

Irrigation helps beat the heat of global warming

17 JANUARY 2020

Large-scale irrigation can help alleviate and even reverse hot extremes driven by human activity and other drivers of global warming, a new international study has found.

The research, led by ETH Zurich in Switzerland, showed that irrigation dampens and in some cases offsets the combined effects of global warming on hot days.

The researchers compared the climate effects of irrigation with other natural and human drivers, including greenhouse gas emissions, across intensely irrigated areas in Southern Europe, North Africa, South Asia, and the United States.

Dr Annette Hirsch, from the ANU Research School of Earth Sciences, was part of the research team.

She said while not a “watershed”, the study showed that irrigation offered some hope when it came to dealing with more frequent and intense hot extremes caused by global warming.

“There’s no doubt that as the planet warms, we will face even hotter extremes more frequently,” Dr Hirsch said. “Many studies show that under global warming, the chances of hot extremes across the planet are increasing.

“But what we found was that while global warming has increased the chances of hot extremes across the planet, in some regions expanding irrigation reduces that effect or can even reverse it.

“Our results show heat extremes are partly or completely offset by the cooling effects of irrigation.

“In this case, irrigation has the same effect for a hotter planet as pumping up the evaporative cooler in your house.”

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