‘Cool Farms’ Mask Global Warming

Facts matter: Sign up for the free Mother Jones Daily newsletter. Support our nonprofit reporting. Subscribe to our print magazine.


You’ve heard of urban heat islands that generate pockets of hot air. Now researchers confirm the existence of their opposite: cool farm patches that tend to cool things down, reports New Scientist. These have been felt in California for more than a century, in areas of intensive irrigation, like the Central Valley, where “cool farms” have counteracted global warming. Researchers from the Lawrence Livermore National Laboratory, extrapolating back to when irrigation began in 1887, calculate that intensively irrigated parts of the Central Valley are ~3.0 to 5.75°F cooler than they would otherwise have been. The cooling happens because much of the solar energy hitting irrigated ground during the day goes to evaporate the extra water in the soil and plants instead of heating the air. The cool farms could explain why minimum and maximum winter temperatures steadily rose in California between 1915 and 2000, while maximum summer temps did not. The warmer winters can only be explained by the greenhouse effect, and the authors speculate the cool-farms effect may have masked the impact of global warming on summer temps — since irrigation is mostly carried out during the summer.

But the cool times may not last. A rollback of the cooling effect of irrigation in the face of continued global warming could mean that California will be hit by substantial warming. This could also mean that irrigated regions around the world, which now provide about 40% of global food production, will feel more than their share of warming in the future, with the obvious impact on food security. . . So, plant your water gardens now. JULIA WHITTY

THE END...

of our fiscal year is Thursday, June 30, and we have a much larger fundraising gap than we can easily manage with only days left to go.

Right now is no time to come up short: If you value the hard-hitting, democracy-protecting, justice-advancing journalism you get from Mother Jones, please help us keep charging as hard as we possibly can with a much-needed and much-appreciated donation today.

payment methods

THE END...

of our fiscal year is Thursday, June 30, and we have a much larger fundraising gap than we can easily manage with only days left to go.

Right now is no time to come up short: If you value the hard-hitting, democracy-protecting, justice-advancing journalism you get from Mother Jones, please help us keep charging as hard as we possibly can with a much-needed and much-appreciated donation today.

payment methods

We Recommend

Latest

Sign up for our free newsletter

Subscribe to the Mother Jones Daily to have our top stories delivered directly to your inbox.

Get our award-winning magazine

Save big on a full year of investigations, ideas, and insights.

Subscribe

Support our journalism

Help Mother Jones' reporters dig deep with a tax-deductible donation.

Donate