40 Years of Atmospheric River Storms Left Staggering Price Tag in Western U.S., Study Finds

Signals Summary: Global warming is making atmospheric river storms more common on the west coast, particularly in California. The extreme precipitation these storms bring are the primary cause of flooding in the western U.S. 

Atmospheric rivers (ARs) are causing billions of dollars in damage in the the western United States, according to a new study.

Flooding caused by atmospheric rivers – long, thin plumes of moisture capable of carrying tremendous amounts of water – has resulted in about $43 billion in damage in western states in the last 40 years, the study by researchers at the Scripps Institution of Oceanography and the U.S. Army Corps of Engineers found.

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The new Scripps study says ARs were responsible for more than 99 percent of all flood damage in some coastal areas of Northern California and Oregon. Relatively high proportions of damage were associated with AR activity in much of Arizona, Idaho and western Montana and as far east as 100 degrees west longitude, which runs from North Dakota to Texas, the study said.

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As the climate warms, the study said, extreme ARs will become more intense as they become wetter, longer, and wider. This is already happening in the Pacific Ocean, the study added.

"Modest increases in AR intensity could lead to significant increases in damages," the study said.