Environment

Are Britain's Floods Linked to Global Warming?

posted: 24 July 2007 11:39 am ET

: Two cars are left stranded after torrential rain caused flash flooding on a road in Wallington, South London, Friday, July 20, 2007. Credit: AP Photo/Sang Tan

Though Britain is known for its typically rainy climate, the torrential downpours of the past month have been anything but typical. The relentless rains have brought central Britain the worst floods it's seen in half a century, and some wonder whether global warming might be to blame.

But that link is hard to make, scientists say.

"We can't link any particular event to climate change," said Jay Larimore, chief of the climate monitoring branch for the U.S. National Climatic Data Center.

But the downpours and floods are consistent with what climate change models predict will happen, said Tim Evans of the Chartered Institution of Water and Environmental Management in the United Kingdom.

Poor land use practices, such as paving large parking lots that make it easier for water to flow across the land, also play a part in increasing the severity of floods, Evans added.

Jeffrey Yin, a meteorologist with the U.S. National Center for Atmospheric Research (NCAR) explained that patterns and changes have to be observed over long periods of time before they can be linked to something like global warming, which acts over longer time scales than any single weather event.

"I would want to see sort of a sustained pattern over a longer period of time, at least 10 to 20 years," Yin told LiveScience. "The issue with extreme kinds of events is that because they're rare, it's hard to say statistically that there's been a shift or a change."

Extremes to become the norm?

Long periods of rain like this are nothing new and occur when certain air patterns persist and keep strong low-pressure systems, associated with heavy rain, over an area for days or weeks on end, Larimore explained.

"They've happened before in the past, they'll happen again in the future," he told LiveScience.

But even though deluges will happen, global warming will increase the likelihood of their happening by changing the environment, said NCAR climatologist Kevin Trenberth.

"In particular, the water vapor in the atmosphere has increased about 4 percent over the oceans since 1970 on average, and this leads to heavier rainfall events by about double that amount," Trenberth said in an email.

Global warming might also make future floods worse.

"This is consistent with the kinds of things we expect from global climate change warming," Trenberth said.

Scientists predict that extreme weather events like the floods in Britain will become more frequent in places all over the world--China too has seen intense rains and flooding this summer.

"People should get used to them," Larimore said.