Global Warming: The Culprit?

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Do we have the time to avert even a relatively slow climate change, or at least the nimbleness to survive it? That's what a lot of scientists are trying to determine. Japanese climatologists, for example, are using the Earth Simulator in Yokohama--one of the most powerful supercomputers in the world--to develop climate models that are more and more sophisticated. Scientists like geologist Claudia Mora of the University of Tennessee at Knoxville are going in another direction, studying isotopes locked in old tree rings to look for clues to past eras of heavy and light rainfall. Pair that information with global-temperature estimates for the same periods, and you can get a pretty good idea of how heat and hurricanes drive each other. "We've taken it back 100 years and didn't miss a storm," said Mora.

It's impossible to say whether any of that will convince the lingering global-warming skeptics. What does seem certain is that the ranks of those skeptics are growing thinner. In Washington successive administrations have ignored greenhouse warnings, piling up environmental debt the way we have been piling up fiscal debt. The problem is, when it comes to the atmosphere, there's no such thing as creative accounting. If we don't bring our climate ledgers back into balance, the climate will surely do it for us. --Reported by Mike Billips/Atlanta, Rita Healy/Denver, Kristin Kloberdanz/Chicago, Terry McCarthy/Los Angeles and Siobhan Morrissey/Miami

[This article contains a complex diagram.  Please see hard copy or pdf.]

HURRICANE RITA

A VICIOUS CYCLE

Over the past 35 years, the number of hurricanes each season has remained constant, but their average intensity has increased, with the number of Category 4 and 5 storms--the most powerful--nearly doubling. Given the swelling populations along the coasts, the danger from monster hurricanes like Rita and Katrina has risen dramatically

1 AREAS OF LOW PRESSURE over the ocean draw in air from surrounding, higher-pressure areas. The earth's rotation makes those winds spiral counterclockwise in the northern hemisphere

Low pressure area

High pressure areas

2 MOIST AIR WARMED by the heat of the ocean rises through the storm, intensifying the suction effect. Eventually the storm dumps some of its water as rain, which falls away and can then be pulled in again

Light winds

Warm ocean water

3 IF STRONG ATMOSPHERIC WINDS don't break this cycle, the storm becomes a hurricane when spiraling air speeds reach 74 m.p.h. (119 km/h), forming a vortex of rain-laden clouds that circle a calm eye

Storm surge

Warm, moist ascending air

Cool descending air

Eye

Area of heaviest rain and highest wind speeds

Spiral rain bands

Warm, moist air

Warm ocean water

Significant hurricane-force winds can extend 40 to 100 miles (64 to 161 km) from the eye

The longer a hurricane stays over warm waters like those in the Gulf of Mexico, the stronger it gets

For a hurricane to form, ocean water has to be at least 80 F (27 C) to a depth of 150 ft. (46 m)

Hurricanes are getting more powerful ...

Number of CATEGORY 4 AND 5 hurricanes in each 15-year span, by ocean

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