for National Geographic News
Global warming could make extreme rains stronger and more frequent than previously forecast, a new study suggests.
Such a scenario could make floods fiercer, damage more crops, and worsen the spread of diseases such as malaria, scientists say.
Rainfall patterns are already shifting as Earth warms under a blanket of humanmade greenhouse gases, experts say.
Study co-author Richard P. Allan, an atmospheric scientist at the University of Reading in Berkshire, United Kingdom, said previous studies have shown that "wet regions are becoming wetter, and dry regions drier."
The study team analyzed satellite images of rainfall over tropical oceans over nearly two decades, from 1988 to 2004.
The researchers found that during El Niño years, which tend to be warmer, rain fell in heavier showers. An El Niño is a climate event where the flow of abnormally warm surface Pacific waters temporarily changes global weather patterns.
"This is something that climate models had predicted," Allan said. "But getting the data from observations is very important."
Many previous rainfall pattern studies have relied on measurements from rain gauges. Such gauges are sparsely distributed across land, Allan said, whereas satellites can see large areas as a whole.
Global Warming Forecast
Although our planet is warming overall, Earth's climate still varies between warmer and wetter El Niño years and cooler and drier La Niña years.
Looking at these changes in rainfall can give scientists a good estimate of what will happen with continued global warming, according to Allan and his co-author, Brian Soden of the University of Miami in Florida.
With continued global warming, the changes in Earth's rainfall patterns will be worse than previously forecast, Allan and Soden write.
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