Global Warming: The Culprit?

What's more, historical studies of hurricanes like Emanuel's rely on measurements taken both before and during the era of satellites. Size up your storms in radically divergent ways, and you're likely to get radically divergent results. Even after satellites came into wide use--adding a significant measure of reliability to the data collected--the quality of the machines and the meteorologists who relied on them was often uneven. "The satellite technology available from 1970 to 1989 was not up to the job," says William Gray of Colorado State University. "And many people in non-U.S. areas were not trained well enough to determine the very fine differences between, say, the 130-m.p.h. wind speed of a Category 4 and, below that, a Category 3."

There's also some question as to whether there's a subtler, less scientific bias going on, one driven not by the raw power of the storms but by where they do their damage. Hurricanes that claw up empty coasts don't generate the same headlines as those that strike the places we like to live--and increasingly we like to live near the shore. The coastal population in the U.S. jumped 28% between 1980 and 2003. In Florida alone, the increase was a staggering 75%. Even the most objective scientists can be swayed when whole cities are being demolished by a hurricane.

"The storm activity this year is not necessarily higher than in previous high-activity years. It's just where they are going," says meteorologist Stan Goldenberg of the National Oceanic and Atmospheric Administration in Key Biscayne, Fla. "If you've got a guy shooting a machine gun but he's not shooting toward your neighborhood, it doesn't bother you."

Even correcting for our tendency to pay more attention to what is happening in our backyard, however, the global census of storms and the general measurement of their increasing power don't lie. And what those measurements tell scientists is that this already serious problem could grow a great deal worse--and do so very fast.

Some scientists are studying not just climate change but the even more alarming phenomenon of abrupt climate change. Complex systems like the atmosphere are known to move from one steady state to another with only very brief transitions in between. (Think of water, which when put over a flame becomes hotter and hotter until suddenly it turns into steam.) Ice cores taken from Greenland in the 1990s by geoscientist Richard Alley of Pennsylvania State University show that the last ice age came to an end not in the slow creep of geological time but in the quick pop of real time, with the entire planet abruptly warming in just three years.

"There are thresholds one crosses, and change runs a lot faster," Alley says. "Most of the time, climate responds as if it's being controlled by a dial, but occasionally it acts as if it's controlled by a switch." Adds Laurence Smith, an associate professor of geography at UCLA who has been studying fast climate change in the Arctic: "We face the possibility of abrupt changes that are economically and socially frightening."