Hurricane forecasts will be different this year

This June, for the 33rd consecutive year, tropical meteorologists at Colorado State University in Fort Collins will release a forecast of the impending Atlantic hurricane season. But for the first time, William Gray will not be around to announce the prediction. The pioneering meteorologist, who invented the seasonal hurricane forecast, died last month at age 86.

Gray revolutionized scientists’ understanding of virtually every facet of tropical cyclones—how they form, what makes them move, why they intensify—an expertise that emboldened him to predict hurricane activity months in advance. Yet strangely, Gray also used his mastery of the heat-driven workings of the tropics to argue against anthropogenic climate change.

Gray’s influence on tropical meteorology is apparent after a quick look at the resumés of leaders in the field: Christopher Landsea of the National Oceanic and Atmospheric Administration, Greg Holland of the National Center for Atmospheric Research, and dozens of others got their start with Gray. “Dr. Gray was quite a mentor for me,” Landsea says.

By 1984 Gray had already cemented his place as a leading authority on hurricanes and atmospheric circulation patterns that form cumulus clouds. But he really took the field by storm in June of that year, when he predicted that 10 named storms, 7 of them hurricanes, would form in the Atlantic by November. He shrewdly recognized that a couple of climatic factors, including the absence of El Niño in the Pacific and low atmospheric pressure in the Caribbean, portended a more active season in the Atlantic. “Recognizing that the state of the tropical Pacific could influence Atlantic hurricanes months later is a pretty nice leap,” says Gabriel Vecchi , a climate scientist at the Geophysical Fluid Dynamics Laboratory in Princeton, New Jersey. “It’s really hard to overstate the importance of this piece of work.”

Gray didn’t do too badly on his first forecast . The 1984 season featured two fewer hurricanes and two more named storms than he predicted. Today numerous teams of meteorologists in academia and government, including the CSU team led by Gray protégé Philip Klotzbach , release largely reliable seasonal hurricane forecasts.

Over the past decade, Gray drew far more attention for his views on climate than on his bread-and-butter area of expertise. The vast majority of climate scientists agree that water vapor, a potent greenhouse gas, feeds into a vicious cycle: As carbon dioxide traps heat, the atmosphere will hold more water vapor, which will then trap more heat.

Gray came to a different conclusion. It’s important to note that he didn’t doubt the effect of human activity on altering the thermodynamics of the atmosphere. But he determined that the hydrological cycle would dampen or even reverse the impact of carbon emissions. The tropics would become rainier, he argued, which would dry out the air above and permit heat to escape into space. Gray described this mechanism in talks but barely wrote up his ideas.

According to most climate modeling and observational evidence, Gray’s arguments don’t hold up. “I don’t think [Gray’s] work on climate change was at the same level as his work on hurricanes by any measure,” Vecchi says. Nonetheless, Klotzbach plans over the next few months to compile and release some of Gray’s research—not because he agrees with it, but because he believes the community should have the chance to evaluate the arguments of someone who knew a thing or two about the atmosphere over the tropics.

Klotzbach says that Gray, never one to shy away from debate, wasn’t bothered by the notoriety he received for his controversial views. “I don’t think he really cared,” Klotzbach says. “For better or worse, that’s what he believed.”