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Central Valley could see more ‘dangerously hot’ days from climate change. Here’s how many

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California’s Central Valley is no stranger to heat, but human-caused climate change could soon see the region hitting boiling temperatures at greater frequency than before.

That’s the finding of the Union of Concerned Scientists, a nonprofit organization founded “to use the power of science to address global problems and improve people’s lives,” according to the group’s website.

The American Southwest could see an average of five weeks a year of temperatures above 100 degrees, more than three weeks of days with temps above 105 and 10 days a year so hot they are “off the charts,” or greater than 127 degrees, according to a report from the organization titled “Killer Heat in the United States: Climate Choices and the Future of Dangerously Hot Days.”

All this will come to pass “by the end of the century if no action is taken to reduce global warming emissions, with Arizona, California and New Mexico seeing the largest rise in extreme heat,” according to the report.

In the Central Valley, hot temperatures will grow much more frequent in the coming decades.

Sacramento County saw an average of five 100-degree days in 2000. In 2036, that number will increase to 31 days a year, on average. By 2070, Sacramento County could see 62 days of 100-degree weather a year.

And that’s just 100 degree heat.

Sacramento County also could see 12 days of 105 degree heat by 2036 and 35 days of 105 degree heat in 2070. The county also could see an average of six days of “off the charts” heat every year by 2070, according to the group.

Elsewhere in the Valley, there would be similar jumps in extreme heat:

Fresno County had an average of seven days of 100 degree heat in 2000. In 2036, that average will be 29 days a year. By 2070, it’ll be 49 days a year. Fresno County also will see nearly two weeks of 105-degree heat by 2036 and more than four weeks by 2070. The county also will see six days of “off the charts” heat a year by 2070.

Stanislaus County had an average of five days of 100 degree heat in 2000. In 2036, that average will be 30 days a year. By 2070, it’ll be 58 days a year. Stanislaus County also will see 11 days of 105-degree heat by 2036 and 31 days by 2070. The county also will see five days of “off the charts” heat a year by 2070.

Merced County had an average of seven days year of 100 degree heat in 2000. In 2036, that average will be 38 days a year. By 2070, it’ll be 68 days a year. Merced County also will see 15 days of 105-degree heat by 2036 and 39 days by 2070. The county also will see seven days of “off the charts” heat a year by 2070.

“Our analysis shows a hotter future that’s hard to imagine today,” said Kristina Dahl, co-author of the report. “Nearly everywhere, people will experience more days of dangerous heat even in the next few decades.”

The report held out some hope, though even the best case scenario cautions that extreme heat is inevitable. With significant reduction of greenhouse gasses, the Central Valley could see the number of extreme heat days reduced to between 21 and 22 days a year on average.

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Andrew Sheeler covers California’s unique political climate for McClatchy. He has covered crime and politics from Interior Alaska to North Dakota’s oil patch to the rugged coast of southern Oregon. He attended the University of Alaska Fairbanks.
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