West Likely to Be Stormier with Climate Change

The types of storms that have been bringing heavy snow and rain to the West this winter, triggering landslides and floods while easing stubborn droughts, are likely to become stronger and more frequent, according to the results of a conclusive new study.

The drenching storms have been falling from atmospheric rivers — high-altitude streams of moisture that carry much of the West’s water from the Pacific Ocean in sometimes-violent spurts that can lead to floods.

The latest study to project an increase in the frequency and ferocity with which atmospheric rivers will reach the West Coast was published over the weekend in Geophysical Research Letters. Scientists described the analysis as more robust than earlier ones.

Days on which atmospheric rivers reach the West Coast each year could increase by a third this century, if greenhouse gas pollution continues to rise sharply, Pacific Northwest National Laboratory researchers concluded after running model simulations.

Currently, the West Coast is likely to receive rain or snow from atmospheric rivers between 25 and 40 days each year, the analysis concluded.  By century’s end, that’s expected to rise to between 35 and 55 days annually.

Meanwhile, the number of days each year on which the atmospheric rivers bring “extreme” amounts of rain and snow to the region could increase by more than a quarter.

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