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Global Warming Is Causing Humidity To Rise, Study Says

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By NEIL JOHNSON, The Tampa Tribune

Published: October 12, 2007

TAMPA - Just what Florida needs, more humidity.

A study reported this week in the scientific journal Nature says global warming is causing humidity to rise. In the Sunshine State, that could mean more intense but fewer thunderstorms, more fuel for hurricanes, and a higher misery quotient during summer.

Oh, yeah, and lots of exploding hairstyles. Humidity is death to 'dos.

'It makes hair swell and explode. If there are broken ends, they pop out,' said Fran Fernandez, owner of Artistic Hair and Make-Up by Fran Fernandez in South Tampa.

'Then all women are in a bad mood. When it's dry and cool, women are happy.'

The new study, done by a team of scientists in the United States and United Kingdom, showed humidity levels rising and cited computer models showing that greenhouse gases from human activity are to blame.

The study built on earlier research by scientists at the National Center for Atmospheric Research in Boulder, Colo., that revealed a link between rising temperatures and the amount of humidity in the atmosphere globally.

'We found a very strong relationship,' said Kevin Trenberth, head of climate analysis at the Colorado center.

The reason is simple: Warmer air holds more water vapor - what we call humidity.

Trenberth said his study found the amount of water vapor in the air increased about 3.5 percent from 1988 until 2006. Since 1970, that increase has totaled about 5 percent.

Two decades from now could see another 3 percent to 4 percent boost in humidity, Trenberth said.

The latest study ran data through climate models that calculated the impact of additional greenhouse gases that trap heat, such as carbon dioxide, and found that results matched data from current measurements.

Additional humidity puts more potential rain into the atmosphere, and that could increase the intensity of afternoon thunderstorms, though they would be fewer and more scattered because they rain themselves out quickly, Trenberth said.

Water vapor and heat are the twin fuels for tropical cyclones. But not all scientists agree that rising temperatures are creating more and stronger hurricanes.

Increased humidity also means a higher heat index or 'feels like' temperatures during our soupy, hot summer afternoons.

The rise in humidity the past quarter-century would correspond to a 1 degree increase in the dew point, which is a measure of the amount of water vapor in the air.

When the dew point rises above 60 degrees, we begin to feel uncomfortable. When it hits 70, we swelter.

You just have to look back to last week when the dew point ran in the 73 to 75 degree range to remember how stifling the afternoons seemed. With dew points in that range, overnight temperatures stayed in the middle 70s.

The next 20 years of warming could add another degree to the dew point, Trenberth said.

Reporter Neil Johnson can be reached at (813) 259-7731 or njohnson@tampatrib.com.

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