Hurricanes 'to Get Stronger'

Hurricanes are likely to get more extreme as a result of climate change, say scientists.

Computer models of the Earth's water cycle suggest that hurricanes will intensify as warmer temperatures draw more ocean water into the atmosphere.

The research follows a record number of hurricanes affecting Florida and typhoons striking Japan last year.

Kevin Trenberth, a researcher at the National Centre for Atmospheric Research in Colorado, who led the research, said warmer seas and increased atmospheric water vapour would add energy to the showers and thunderstorms that fuel hurricanes. "Computer models also suggest a shift ... toward extreme hurricanes," he said.

Most of the hurricanes that strike the US coastline are formed in the tropical north Atlantic, where sea-surface temperatures over the past decade have been the warmest on record.

"Over the 20th century, water vapour over the global oceans increased by 5% and that probably relates to about a 5% increase in intensity and probably a 5% increase in heavy rainfalls," says Dr Trenberth, whose research is published today in Science. "That relates directly to the flooding statistics."

Present models suggest a 7% increase in the moisture in the atmosphere for every degree celsius that the earth warms. As the carbon dioxide in the atmosphere increases and global temperatures rise, so the amount of water in the atmosphere goes up.

However, the effect of climate change on hurricane numbers and landfalls is uncertain, said Dr Trenberth.

Models disagreed on how global warming might affect the wind sheer that can either support or discourage hurricane formation.

The number of hurricanes and typhoons tends to hold steady from year to year. When activity increases in the Atlantic, it often decreases in the Pacific, and vice versa. So, it is hard to make long term predictions on the number of storms or how they will move.

"There is no sound theoretical basis for drawing any conclusions about how anthropogenic climate change affects hurricane numbers or tracks, and thus how many hit land," said Dr Trenberth.

Temperatures across much of the country are likely to hit highs of 32C (90F) this weekend, the Met Office said yesterday. Its forecasters warned that the high temperatures may cause health problems for elderly people.