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Tuesday, October 05, 2010

Climate change yields higher water levels and more extreme rainfall

Study: Climate change yields more extreme rainfall; water rises

Water levels in the world's rivers and oceans rose 18% over a 13-year period ending in 2006, due in part to melting polar ice sheets, according to a scientific analysis by the University of California, Irvine. The so-called water-cycle acceleration could result in more water availability, but it will likely lead to more extreme wet and dry climates around the world, a sign of global warming, the study's lead author said. The Orange County Register (Calif.)
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Warming sign: harder rain, higher rivers

By PAT BRENNAN
ORANGE COUNTY REGISTER

Rainfall is intensifying, rivers are rising and water flow into the ocean is increasing rapidly, a new UC Irvinestudy shows -- a possible "warning sign" of higher sea levels and global warming.

Satellite and surface measurements over 13 years revealed an 18 percent increase in the flow of water from rivers and melting polar ice sheets into the world's oceans, according to the study, likely one of the first of its kind, to be published this week in the Proceedings of the National Academy of Sciences.

"Those are all key indications of what we call water-cycle acceleration," said Jay Famiglietti, aUC Irvine Earth System Science professor and lead investigator on the study. "That is a very important and anticipated outcome of climate change."

Planetary warming includes higher ocean temperatures, which increase evaporation; higher air temperatures drive more evaporation as well, Famiglietti said.

That means more fuel for monsoons, hurricanes and storms over land.

"You're talking a lot more energy transfer between the surface and the atmosphere," he said. "We're expecting much more energetic storms, and that translates into the potential for more extreme events."

During the study period ending in 2006, the scientists saw an average 1.5 percent increase in water flows per year. They relied largely on radar data from NASA satellites, instead of computer models, to calculate the flows.

And while 13 years is probably too short a time frame to remove any doubt, the consistent trend of higher flows leaped out at the researchers.

"Although there are a lot of ups and downs in the data sets, the trends are all the same," Famiglietti said.

Such changes might sound potentially beneficial -- more water, more water availability. But if the water cyle is growing more extreme, that likely means extremes in both wet and dry climates around the world -- catastrophic flooding in some places, intensifying drought in others.

No single storm or weather event can be directly linked to global warming, which is measured in averages over decades. But recent catastrophic flooding in Pakistan is a powerful example of what may be ahead if the trend-line continues.

"We always need more data, but we don't want to stick our head in the sand," Famiglietti said. "This is an early warning, a glimpse of the future."

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