West to get one or two more extreme weather strikes

One or two blows from unpleasant forest fires, followed by heavy rains causing floods and landslides, will hit the Western United States much more often in a warming world, becoming a common occurrence, a new study says.

This combination of fire and floods, with extreme floods hitting a site that burned within a year, could increase up to eight times in the Northwest Pacific, double in California and jump about 50% in Colorado by 2100 in the worst case scenario Climate change scenario to increase greenhouse gas emissions, according to a study in Friday’s Science Advances.

The study says that as man-made climate change intensifies, 90% of extreme fires will be followed by at least three extraordinary rains in the same place within five years.


The authors of the study said that this is because although the West is generally drier – which prolongs the season of forest fires – concentrated bursts of heavy rain are increasing and coming earlier, so areas may be affected by both extremes.

“One disaster is bad. Two disasters in a row are even worse because you’re already rocking the first one, “said study co-author Samantha Stevenson, a climatologist at the University of California, Santa Barbara. “But in this particular case of forest fires plus extreme rains, forest fires have worse consequences because you lose your vegetation, change soil properties and make this landscape more conducive to destructive flooding.”

Stevenson knows because Thomas’ fire, which began in late 2017 and was followed a month later by half an inch (13 millimeters) of rain in just five minutes, caused muddy landslides in Montecito that killed 23 people.


“Oh, yes, it was crazy,” Stevenson said. “It was as if the whole highway was blocked like a mud wall. There were stones in people’s living rooms. “

For study co-author Daniel Swain, a Western time expert at UCLA who lives in Colorado, this struck even closer to home. Last week, he had to evacuate his home in Boulder because of a fire. Today is the beginning of the season of flash floods.

Especially in the Northwest Pacific, the seasons of fires and floods continue to grow longer and closer together. While both are likely to worsen, extreme rainfall needs to increase more, Swain said.

“It’s another kind of double blow, a situation where the candle burns at both ends,” Swain said. “It is quite predictable that some of these places will literally still be on fire when the first extreme rains put them out.


The report examines 11 western US states, focusing on four of them, where the projected increase in fires followed by torrential rains is most noticeable.

The study’s authors acknowledge that the worst-case warming scenario they’ve studied using dozens of large-scale climate model simulations is becoming less likely as many, but not all, countries, including the United States and Europe, reduce emissions. heat capture gases.

They said they were not able to use simulations of more likely scenarios with some moderate emission reductions at the time. But in more likely scenarios, the Pacific Northwest is likely to see a fourfold increase in fires and floods, said lead author Daniel Tuma, a climatologist at the National Center for Atmospheric Research.

The simulations were at the time of the fire, not the fires and rain conditions themselves. Leroy Westerling, a climatologist at the University of California, Merced, who was not part of the study, said he was concerned about the accuracy of global simulations of computer models that could run on such a small scale. However, he said, the results make sense.



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Follow Seth Borenstein on Twitter at @borenbears.


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West to get one or two more extreme weather strikes

Source link West to get one or two more extreme weather strikes

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