Changing climate blows a fiercer wind
Scientists predict more severe weather and a rise in hurricane activity in the future
Droughts, heavy downpours, excessive heat and intense hurricanes "are likely to become more commonplace" with increasing greenhouse gases in the atmosphere, national climate experts predict.
They discussed highlights of the first comprehensive analysis of weather changes and climate extremes in North America, Hawaii, the Caribbean and U.S. Pacific islands in a teleconference yesterday.
Gerry Meehl, senior scientist at the National Center for Atmospheric Research in Boulder, Colo., said there is a 90 percent or greater probability of rainfall extremes.
The northern half of the United States particularly might see very heavy rainstorms once in about every five years in the future, compared with once in every 20 years in the past couple of decades, he said.
"These increases in heavy downpours and probability of events increasing ... can lead to the type of events we're seeing in the Midwest."
Of interest to Hawaii and Pacific islands, the National Oceanic and Atmospheric Administration officials said future hurricanes likely will have stronger winds and much more intense precipitation. Hurricane activity is linked to sea surface temperatures, which are going to increase, they said.
They noted a "substantial increase" in hurricanes in the Atlantic since 1970, an "increasing tendency" toward hurricanes in the Western Pacific and a "decreasing tendency" in the Eastern Pacific.
"Certainly, if we start to see an increase in sea surface temperatures, it would have an effect on hurricanes," said Ray Tanabe, National Weather Service warning coordination meteorologist in Honolulu.
He said the only statistical correlation between hurricanes and sea surface temperature in the Pacific has been with El Ninos.
Four peak seasons for Pacific tropical cyclones since 1971 occurred during El Nino years when sea surface temperatures in the equatorial region were much higher than normal, Tanabe pointed out.
A lot of hurricanes form in the eastern equatorial region, then move into the Central Pacific, he said.
El Ninos occur in five- to seven-year cycles, Tanabe said. "We're coming out of a La Nina season (when sea surface waters are cooler). We're going to neutral conditions by mid-July." Hurricane season began June 1 and continues through November.
Among other climate change projections:
» Stronger winds and higher extreme wave heights are likely with the strongest cold-season storms in the Atlantic and Pacific.
» Abnormally hot days and nights with heat waves are likely to become more common, and cold nights less common.
» Sea ice will continue to decrease and could disappear in the Arctic Ocean in the summer in future decades.
» Droughts are likely to become more frequent and severe in some regions, such as the Southwest.
The U.S. Climate Change Science Program and Subcommittee on Global Change Research report concludes, "We are now witnessing and will increasingly experience more extreme weather and climate events," said Tom Karl, director, NOAA National Climate Data Center in Asheville, N.C.
Changes in heat extremes likely can be attributed to human activity -- the burning of fossil fuels and increases in heat-trapping gases, the report said.
The climate officials said they could not estimate the cost of future extreme weather events.
Richard Moss, World Wildlife Fund official, in a Business Wire report, said, "To fully grasp the ramifications of the surge in extreme droughts and floods that is forecast in this report, one need only look at the widespread devastation across the Midwest."
The president is asking Congress for $1.8 billion in emergency aid to help the region, roughly the entire annual federal budget for climate change research programs, he pointed out.