Tropical downpours worsening, say scientists
Thu Aug 7, 2008 2:02pm EDT By Alister Doyle, Environment Correspondent
OSLO (Reuters) – Tropical downpours are becoming more frequent and the
trend seems worse than expected, bringing greater risks of flash floods,
scientists said on Thursday.
“As the tropics warm are seeing an increased frequency in the heaviest
rainfall,” said Richard Allan of the University of Reading in England, who
co-authored a study of tropical rains with Brian Soden of the University
The satellite review of tropical rainstorms since the 1980s gave the first
observational evidence to confirm computer models that predict more
intense cloudbursts because of global warming stoked by human activities,
Writing in the journal Science, they also said the trend to extreme
soakings was stronger than predicted by computer models “implying that
projections of future changes in rainfall extremes … may be
The findings were based on a study of the tropical oceans, where
satellites can more easily record rainfall. Allan said the trends were
likely to be matched over land.
The U.N. Climate Panel, drawing on the work of 2,500 scientists, said last
year that rainfall was likely to get more intense in many tropical
regions, raising risks of flash floods, erosion and mudslides.
The satellite data showed 2-3 times more intense downpours than predicted
by the climate models, stoked by rising emissions of greenhouse gases from
burning fossil fuels in cars, factories and power plants.
But Allan told Reuters that the finding that the models were too cautious
was less certain than the conclusion that tropical rainfall had become
more intense. Checks might be made on land by examining rain gauges or
river flows, he said.
The U.N. Climate Panel says that shifts in rainfall patterns are likely to
disrupt farming in many regions, affecting the livelihoods of hundreds of
millions of people especially in Asia, Africa and Latin America.
“Flash flooding can cause damage to settlements and societies. It can
contaminate ground water, drinking supplies, with potential health
effects,” Allan said.
“The spread of disease can be impacted by heavy rainfall,” he added. “Very
intense rainfall can destroy crops. There are also possibilities of
enhanced erosion, degradation of soil”.
Scientists say it is hard to link climate change to one-off events such as
floods in the U.S. Midwest that damaged millions of acres of cropland in
The U.N. Panel predicts more rain overall this century in many parts of
the tropics and towards the polar areas with declines in middle latitudes
such as the Mediterranean basin, the Western United States and southern
(Editing by Andrew Roche)