Hurricane Expert: "New England Really Gets It In The Teeth" As Climate Warms

It was a student who first suggested to MIT Professor Kerry Emanuel that he use a classroom teaching tool to forecast hurricanes.

"I laughed and said, 'No, this is a toy. It's not supposed to be more than that,'" said Emanuel, widely regarded as the world's leading expert on hurricane physics.

"And then I went home and thought about it.'"

Emanuel designed the teaching tool by simplifying the complex programs forecasters use to predict tropical cyclones. It helped students learn how to forecast storms without the need of expensive supercomputers to crunch the numbers. Students could run Emanuel's program on a laptop, maybe even on paper, instead of in a supercooled warehouse full of servers.

He hadn't imagined the simplified tool would do a better job forecasting hurricanes than its complicated predecessors.

"We tried it, and to our amazement it seemed to do a pretty good job of forecasting the intensity of real hurricanes," Emanuel said, to the point that organizations like the U.S. Navy Joint Typhoon Warning Center now use Emanuel's tool, still classified as experimental, as part of a suite of models generating forecasts for naval fleets at sea.

Emanuel has been using the tool—dubbed The Coupled Hurricane Intensity Prediction System, or CHIPS—to forecast hurricanes for a decade now, and he has data showing that it has outperformed more complicated hurricane models, especially when gazing further into a storm's future.

CHIPS has another advantage. Because it's cheap and easy to run, it can be used to process thousands of permutations of possible hurricanes in the planet's future.

Instead of using weather observations from the field, researchers can substitute conditions predicted by global climate models—wind conditions and thermodynamic conditions of the sea and air in a hypothetical climate warmed by greenhouse gas emissions.

And that has empowered Emanuel to predict in some detail how hurricanes may behave in a warmer climate.

If the models prove correct—a big if—New England faces a stormy ride as the climate warms this century.

At an appearance in Chicago this week, Emanuel predicted climate change will not only increase the frequency of the most powerful cyclones, but will alter their tracks so that more plow into the American Northeast.

"New England really gets it in the teeth," Emanuel told about 50 people at the University of Chicago Wednesday, "not so much because of shifting thermodynamic conditions as shifting tracks. The general circulation changes."

Emanuel's studies "suggest some sensitivity of hurricanes to climate state, with increasing incidence of intense storms as the climate warms," he has written.

Specifically, the studies show a marked increase in the Power Dissipation Index, a measure of the amount of energy expended by hurricanes globally. Much of that energy will be expended in the western North Pacific, Emanuel has reported, menacing Japan.

But the climate may also be packing a punch for America's Eastern Seaboard. Locally, Emanuel conducted a study of hurricane risk for the city of New Haven that predicts pronounced increases in the frequency of peak winds and storm total rainfall. Another study, published before Hurricane Sandy, predicted increased storm surge at the southern tip of Manhattan.

Emanuel was the first prominent hurricane scientist to suggest a link between climate change and stronger hurricanes. Three weeks before Hurricane Katrina slammed into New Orleans in 2005, he published a paper showing the Power Dissipation Index had risen dramatically in the previous 30 years and predicting it would continue to do so.

His predictions have sometimes been qualified by other scientists, including the prominent environmental researcher Roger Pielke, Jr., who have made note of uncertainties in the models. But Emanuel has, in kind, challenged other scientists' reticence.

Few scientists dispute, however, that a warmer world means heavier rains from big storms.

"This is something everybody agrees on," Emanuel said. "Hurricanes have to rain more if it gets hotter. It's just really really simple physics. Storm total rainfall is much larger. And that's true almost across the board."

But Emanuel's model also predicts fewer tropical cyclones in the Southwest Pacific and a decline in probable damage from weaker storms everywhere.

Slightly fewer Category 1 hurricanes will cause damage, his model predicts, and slightly more Category 3, 4, and 5 hurricanes will cause damage. But that slight increase in the most powerful storms bears the potential for tremendous damage in casualties and dollars.

Wind speeds for Category 3 hurricanes begin at 111 mph. And even though the most powerful storms account for only 13 percent of landfalls in the historical record, according to Emanuel's research, they have accounted for 90 percent of the damage.

"Reporters always ask me all the time, what's going to happen to the frequency and intensity of hurricanes," he said at Wednesday's seminar, hosted by the Energy Policy Institute of Chicago. "It's not quite the right question. We really want to know what's going to happen to the frequency of the high-end storms."

Category 1 storms occur frequently enough that coastal communities have adapted to them, Emanuel said. Not so with larger storms.

"If we had Category 5 typhoons every year we would be adapted to them.  Maybe we would do what the Mayans did and not build cities on the coast. That's how they adapted."