A group of northern California scientists have found a new bend in the Gordian knot of global warming: coastal cooling.
The team, headed by meteorologist Robert Bornstein of San Jose State University, has found that as temperatures rise in California, so do pressure differences that control cool Pacific winds. That means higher temperatures inland create lower ones at the coast.
"It's not that the whole Earth is warming like an oven," Bornstein says. "Different parts are warming at different rates, therefore the pressure patterns are upset—and therefore the wind patterns are upset."
Bornstein, along with colleagues Jorge Gonzalez and Bereket Lebassi, both of Santa Clara State University, separated historic temperature data for California into smaller groups by factors such as region, time of day and time of year. By comparing the data, they found that daytime summer highs have been dropping at the coast because of cooling higher winds.
The research is part of a growing trend of examining smaller areas to fill in the wider picture of global warming. Wind is a good example: In this case it is lowering temps by bringing cooler air from the ocean; in other instances, it may bring hotter, dryer desert air to the U.S. Southwest; or change the cloud cover over the Pacific Northwest; or shift rain patterns in the nation's South. These smaller scale snapshots are creating a complex and nuanced image of how warming will affect the country —and the world.
Bornstein says the findings bode well for California's wine regions and the Los Angeles Basin, because they indicate that those areas may be spared the worst of climate change. But this also means the rest of the state may end up hotter than expected in 30 years (and probably already are, because cooler coasts have been dragging down the average) if nothing is done to address the causes of global warming.
The study is currently being reviewed to appear in the Journal of Climate.
Climatologist Stephen Schneider, of nearby Stanford University praised the research but disagrees with the conclusions.
"I thought his extrapolation beyond meteorology into the world of climate impacts was wrong," he says. "For him to say that L.A. doesn't have to worry about heat waves—as well as Napa—is just wrong."
Schneider says the key is not daily highs but, rather, extreme highs. He says grapes are damaged and people suffer heat exhaustion and/or stroke mostly on just a few sizzling days during the summer. These are the days where either the wind comes from the east, or does not blow at all. And it is not likely that these days are decreasing, which means slightly cooler days will not make a difference.
"It might help with the air conditioning bill," he says. "Instead of it being 85 in the afternoon, it's 83. That's nice. What I'm worried about is when it's 106, as it was this year, in the future couple decades it will be 108."
Bornstein says he plans to do more research to determine the wind's cooling mechanism. That is, whether the winds have become more frequent, intense and colder—or whether they simply penetrate further inland, cooling more acreage. He also plans to look for a similar effect along the U.S. eastern seaboard.