More Regions of Earth Wet, Dry

By Randolph E. Schmid Copyright 1998 Associated Press August 20, 1998

Regions of Earth experiencing unusually wet or dry conditions have increased over the past 20 to 30 years, researchers say in a report that will add to the debate over global warming.

While the overall trend was small, climate researchers found increases in drought-affected areas in Africa and Asia and an increase in both extremely wet and extremely dry areas in Europe and the United States.

These changes were particularly noted in regions affected by the El Nino phenomenon, a periodic warming of the Pacific Ocean that can affect weather worldwide.

The new analysis is in a paper to be published in the Sept. 1 edition of Geophysical Research Letters.

"There's no overall strong trends that you would really want to put down as a climate change. But some of the relationships seem to have changed, and in particular since about 1976 it seems as though ... in El Nino you get a bigger response in some of the changes around the world than it used to have before then," said Keven E. Trenberth of the National Center for Atmospheric Research in Boulder, Colo., one of the report's authors.

A stronger El Nino response had been reported over Australia by researchers there, Trenberth added, and the new paper found that was also the case elsewhere.

The new findings, the researchers report, "could all result partly from the greenhouse-gas induced climate changes."

Climate researchers say global warming can change the climate in ways that promote drought in some areas and extreme wetness in others. The greenhouse warming theory holds that chemicals added to the atmosphere by industrial processes will trap some of the sun's heat that used to radiate back out to space, resulting in a rise in the Earth's temperature.

While there have been small increases in average temperature in recent decades, the changes have fallen short of predictions, spurring skeptics of the theory. Congress has also been wary of adopting energy-saving measures proposed to reduce release of greenhouse chemicals.

John Christy of the University of Alabama at Huntsville contended that the paper includes "little evidence to point to greenhouse gas-induced climate change."

"Extreme events, because of their rarity, do not typically behave in a statistically even fashion. Thus you should see a trend in them, up or down, over any 100-year period," he said.

And, he added, "How could I fail to mention that the satellite temperatures of the troposphere that we produce here in Huntsville show no warming since 1979?"

Christy's findings, however, have been challenged by researchers who argue that the slow decline in the orbit of the satellites used to measure temperature affects their readings. That has led to debate on whether those temperatures should be revised and what the revisions mean.

In a warmer climate, the new study observes, droughts tend to be longer and more enhanced in drought-prone areas because of increased evaporation. At the same time, this evaporation places more moisture in the atmosphere, leading to the possibility of more flooding in other areas.

Trenberth noted there is evidence of increases in cloudiness that can block out some sunlight and counter warming trends.

The reason for the added clouds may be pollution, he said, but they could also be the result of added moisture in the atmosphere.

Among the study's findings:

_About 50 percent of the Sahel region along the border of the Sahara Desert has been in severe drought since the 1970s, about twice the area in drought in the first half of the century.

_In the 1940s, about 60 percent of Europe experienced "normal" wet or dry conditions. That increased to 80 percent in the 1951-80 period, but drought became a growing problem in southern Europe after 1980.

_In the past 20 to 30 years, the percentage of southern Africa and eastern Asia in drought has increased.

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