| By Lauren Rosenthal Days before hurricane-force Santa Ana wind gusts fueled fires that devastated Los Angeles, meteorologists posted eerily accurate warnings that such a scenario was possible. But they’ve had a harder time pinpointing the role of climate change in events like this. For the last several years, scientists have been debating whether Santa Anas will grow stronger or weaker, more frequent or more rare as the world warms — with little resolution. While some research has shown that these winds will become less common, the dry conditions that prime Southern California for blazes are expected to linger later in the season, colliding with the peak time of year for Santa Anas. “This is really about the drought, compounded by the very intense windstorm,” Craig Clements, director of the Wildfire Interdisciplinary Research Center at San Jose State University, said of the LA fires. Otherwise, “it wouldn’t be this heartbreaking event that’s been unfolding.” The destruction unleashed by the fires, which killed at least 25 people, underscores the urgency of unpacking the science behind Santa Anas. With global warming breaching a key threshold last year and the world failing to meet emissions targets set forth in the Paris Agreement, linking disasters like the California blazes to climate change could strengthen the argument for a renewed focus on net-zero commitments.  Houses burn during the Palisades Fire in the Pacific Palisades neighborhood of Los Angeles on Jan. 7. Photographer: Kyle Grillot/Bloomberg Santa Anas result from a buildup of high pressure over the Great Basin in the western US, which sends air rushing over California’s mountain ranges and out to sea. The mountains channel the winds into powerful gusts, which tend to grow hotter and drier as they roll downhill. These events can last for days at a time, historically arriving in Southern California anytime between September and April. They’ve long been linked to some of the region’s most destructive fires. But in 2019, a well-publicized study showed the Santa Ana season would likely kick off later and later — and that individual windstorms were expected to become less frequent as the world grew warmer. Janice Coen, a project scientist at the National Center for Atmospheric Research, was part of a separate research team that analyzed historical data sets and tried to project future Santa Ana winds as greenhouse gas and aerosol emissions continue to rise. Over time, they predicted that some parts of California would see fewer and fewer Santa Anas. That's partly because the winds are influenced by changing circulation patterns, Coen said, including the jet stream — the fast-moving current of air that encircles the globe. “As the jet stream shifts to the north, these events are much less likely to occur in Southern California,” Coen said of her team’s findings. But even “if humans were doing nothing to the climate,” she added, “there would still be tremendous variability from year to year.” Newer research from the team behind the 2019 report suggests there may be fewer Santa Ana events in the spring and fall as the world warms, but the winds will be hotter and drier. And the parched conditions that amplify fire risk in Southern California will increasingly overlap with the peak of the wind season, which will still fall in December and January. In the near term, scientists agree that drought was a primary climate culprit behind the fires that intensified into a near-uncontrollable fury in LA last week. Winter is typically the city’s rainiest time of year, but since April 1, downtown Los Angeles has received less than an inch of rain — compared with the more than five inches it averages over that period. After two wet winters, Southern California quickly slipped back into drought. Grasses and brush throughout the region are starved of moisture, and any fire that’s ignited since last week has had ample fuel to feed its growth. “We wouldn’t even be talking about this event if LA had its rain,” Clements said. Read and share this story on Bloomberg.com. For weather insights sent straight to your inbox, subscribe to the Weather Watch newsletter. | 
