Global warming is intensifying the monsoon in Central India, according to a study that warns of increasing risk from heavier rains during the season.
The research, published in Science today (1 December), reinforces claims that global warming is boosting the power and number of storms and other extreme weather events across the world.
Heavy monsoon rains in central India between 1981 and 2000 were more intense and frequent than in the 1950s and 1960s, and increased by 10 per cent since the early 1950s. Severe rains doubled over the same period.
At the same time, there were fewer moderate rains, say the team led by B.N. Goswami from the Indian Institute of Tropical Meteorology, Pune, India.
The trends are likely linked to rising global temperatures, Goswami told SciDev.Net.
Scientists had already observed that the Asian monsoon gained in strength over the past few centuries. In 1994, the UN's Intergovernmental Panel on Climate Change warned that global warming could intensify and increase the variability of the monsoon.
But the data on average rainfall in India did not show any substantial change. The study by Goswami and colleagues suggests that this can be explained by the decrease in moderate rainfall and does not point to a stability of the monsoon.
The researchers, who used data from 1803 stations over Central India between 1951 and 2000, explain that previous studies on extreme rainfall trends in India had been inconclusive.
Suruchi Bhatwal, a senior scientist at the Tata Energy Research Institute in New Delhi, told SciDev.Net that Indian climate change research has been constrained by limited resources and models that have made predictions unreliable.
She warned that a future increase in heavy rains would cause floods and crop damage, with drastic effects on agriculture and food security.
More than half the world's population depends on the annual Asian monsoon to bring much-needed water for agriculture and basic human needs.
But the rains can be perilous, causing landslides, flash floods and crop damage as well as social, economic and environmental damage. Surging floodwaters in the 2002 monsoon killed more than 800 people in Bangladesh, India and Nepal, displacing millions of others.
In 2003, a study by the World Meteorological Organization blamed global warming for the record number of extreme weather events such as floods and tornadoes.
Link to full paper in Science
Reference: Science 309, 1088 (2005)