A new study underscores the difficulty of estimating global warming's effect on weather.
Since the devastating 2005 Atlantic hurricane season, scientists have been briskly testing the notion that global warming's fingerprints have already appeared on tropical-cyclone activity worldwide.
Now, a new analysis from the scientist who helped trigger that flurry of studies suggests that the answer to questions about global warming's impact on current tropical cyclone trends may instead be: No, not yet.
The results come from a team led by Kerry Emanuel, an atmospheric scientist at the Massachusetts Institute of Technology in Cambridge, Mass. He focuses on tropical cyclones, and his latest work seems to undercut his own conclusions in a 2005 study on climate change and tropical cyclones. That study, published shortly before hurricane Katrina struck the Gulf Coast, tied a global increase in the power expended by tropical cyclones to rising ocean temperatures in storm-prone areas. Those rising temperatures, in turn, have been linked to global warming.
There's no question, he says, that the old and new work "contradict each other to a degree."
His team drew its results from a new modeling approach it developed.
The research highlights the challenges scientists face as they estimate the effects rising global average temperatures could have on large-scale weather events important to society. It underscores, too, the risks some advocates and critics of climate-change policies face by using a single weather phenomenon as the poster child of the day for their position.
"There are only downsides" to traveling that path, regardless of one's political starting point, says Roger Pielke Jr., a science-policy specialist at the University of Colorado at Boulder. "If there's one thing we know about science, it changes, it evolves, it's counterintuitive, and we learn things we didn't expect before."