Study links warm spells to heavy rain

 
Scientists studying variations in tropical heat and rainfall since the mid-1980s have found a strong link between warm periods and extreme downpours. The observed rise in the heaviest rains is about twice that produced by computer simulations used to assess human-caused global-warming, said the researchers. Other studies have already measured a rise in heavy rains in areas as varies as North America and India, and climatologists have long forecast more heavy rains in a world warmed by accumulating greenhouse gases, but this analysis, using 20 years of satellite measurements by  the national Aeronautics and Space Administration, is the first to find a strong statistical link between warmth and extreme downpours, the researchers said. The study was published on Thursday in the online journal Science Express. The authors were Richard P.Allan of the University of Reading in England and Brian. J.Soden at the University of Miami. A general relationship between warming and heavier rainfall is widely  accepted; the new paper is important " because it uses observations to demonstrate the sensitivity of extreme rainfall to temperature", said  Anthony J.Broccoli, the director of the Centre for Environmental Prediction at Rutgeres University. "Flash flooding is produced by the extreme rain events", he said. "In the U.S., flooding is a greater cause of death than lightning or tornadoes, and presumable poses similar risks elsewhere. In developing countries, cities with poor drainage routinely grind to a halt and see outbreak of water-borne disease after extreme rainstorms. Such downpours have been estimated in some such countries to blunt economic growth by several percentage points, according to World Bank experts.

The Hindu, 9th August 2008