‘Monsoons could last 10 days longer’

Global warming can lead to dramatic changes in the annual southwest monsoon, says expert

One of the many consequences of global warming could be dramatic changes in the annual southwest monsoon, Govindswamy Bala, associate professor at the Indian Institute of Science (IISc.), has said.

The Intergovernmental Panel on Climate Change (IPCC) has predicted an increase in the duration of monsoon by 10 days and an increase in rainfall intensity by 10 per cent by the end of this century, said Dr. Bala, who is faculty with the IISc.’s Centre for Atmospheric and Oceanic Sciences. He was delivering a lecture on climate change, organised by the Institution of Engineers here on Thursday.

This year’s delay

Asked about the delay in the monsoon’s onset this year, he said the monsoon was historically known to have big annual variability, “even without the influence of climate change”. For instance, “We have seen complete failure of monsoon, where the quantum of rainfall has been 60 per cent below normal,” he said.

The increase in atmospheric carbon dioxide concentrations — primarily from fossil fuel emissions — will impact oceans far more intensely than the earth’s landmass, he said. Oceans were turning acidic from the atmospheric carbon dioxide they absorb, spelling dire consequences for marine life.

Sea levels were expected to rise by a metre by the end of this century, mainly from melting glaciers and from the thermal expansion of water due to global warming, he said. “Most coastal areas could see a 60 cm rise in sea levels.”

The average global temperature had risen by 1 degree Celsius since pre-industrial times, which was a very significant increase, he said. “If we were to see an increase of 2 degrees Celsius, sea levels would rise by 5 metres, according to the IPCC’s calculation.” The last time the planet’s atmosphere had such high concentrations of carbon dioxide (currently 400 ppm) was 3 million years ago, he said.