Error Correction Means California’s Future Wetter Winters May Never Come

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Correcting for the double-ITCZ bias, a persistent error in many climate models, reveals that future U.S. Southwest winters will be drier than expected

California and other areas of the U.S. Southwest may see less future winter precipitation than previously projected by climate models. After probing a persistent error in widely used models, researchers at the Department of Energy’s Pacific Northwest National Laboratory estimate that California will likely experience drier winters in the future than projected by some climate models, meaning residents may see less spring runoff, higher spring temperatures, and an increased risk of wildfire in coming years.

Earth scientist Lu Dong, who led the study alongside atmospheric scientist Ruby Leung, presented her findings at the American Geophysical Union’s fall meeting on Tuesday, Dec. 1, and will answer questions virtually on Wednesday, Dec. 16.

As imperfect simulations of vastly complex systems, today’s climate models have biases and errors. When new model generations are refined and grow increasingly accurate, some biases are reduced while others linger. One such long-lived bias in many models is the misrepresentation of an important circulation feature called the intertropical convergence zone, commonly known as the ITCZ.

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