Wet and Dry Spells in South Asia Growing More Extreme

Extremes in wet and dry spells in South Asia are putting the region more at risk of flooding and drought, a study over the last 60 years reveals in the journal Nature Climate Change.

The South Asian monsoon season during summer greatly impacts agriculture, an industry that sustains 60 percent of India's people and is the source of 70 percent of the country's exports, according to Climate News Network.

A lot rides on monsoons, the report indicates, as they are responsible for 85 percent of India's annual precipitation. But there is a fine line between too little and too much rain.

For example, researchers note that during critical crop growth stages, too many rainless days can lead to crop failure, which is detrimental to India's agriculture-dependent economy. At the same time, short periods of very heavy rainfall can result in natural disasters, such as in 2005, when massive flooding in Mumbai killed thousands of people.

"We are looking at rainfall extremes that only occur at most a few times a year, but can have very large impact," senior author Noah Diffenbaugh, associate professor of environmental Earth system science, said in a statement.

Using unique statistical methods, researchers discovered that although the average total rainfall during the monsoon season has declined, the variability of rainfall during the peak monsoon months has increased. In particular, wet spells intensified and dry spells became more frequent.

"The statistical techniques show that the changes in these characteristics are robust and that these changes are unlikely to happen purely by chance," student collaborator Deepti Singh added.

Changes in the winds and moisture also are likely responsible for the fluctuating weather patterns, the team noted. They intend to investigate further the origin of the atmospheric shifts, but aren't jumping to conclusions.

"There are many predictions that global warming should cause heavier downpours and more frequent dry spells," Diffenbaugh said. "That's what we've found here, but India is a complex region, so we want to be sure before we point the finger at global warming or any other cause."