As Earth warms up, South India to bear the maximum brunt

Southern India is more prone to weather extremes as the earth warms up, according to a study by the Indian Institute of Technology (IIT) in Gandhinagar.
The earth is expected to warm up somewhere between 2.6 degree and 8.5 degree Celsius over the century.

The study, published recently, also states that compared to the worst-case scenario, the best-case scenario will cut down the severity and frequency of floods by 50%. “South India is more sensitive to changes in temperature,” says Vimal Mishra, associate professor at the IIT and the author of the research paper published in the journal, Weather and Climate Extremes.

All models show that extreme weather events — very heavy rains, long dry spells, heat waves — will increase as the average global temperature rises. However, it is not easy to predict what will increase, and in which location. Indian climate scientists are now studying extreme events more deeply to understand the response of the monsoon system to a warming earth.

While scientists have been intrigued by recent extreme weather events, they also point to ominous signs in the last few years. Kerala was pounded by extremely heavy rainfall for two years in succession, while monsoon in the state has been slowly decreasing over the last half century. Meteorologists say although the monsoon is regularly producing extreme rainfall in parts of the country, the mean rainfall has not been increasing over the last few decades.

A combination of extreme rainfall and weakening monsoon is expected to increase droughts, but climate scientists and meteorologists are not confident about the ability of models to predict accurately what will happen to the monsoon over the next few decades. They are, however, sure that heavy spells of rain will continue to increase irrespective of whether the monsoon increases or decreases in strength. “We can say with confidence that the magnitude and frequency of floods will increase,” says Roxy Mathew, climate scientist at the Indian Institute of Tropical Meteorology in Pune. “But we don’t know whether droughts will increase.”

Around the world, roughly $30 billion is lost every year due to extreme events. Mathew had calculated — using the database EM-DAT — that India had lost $60 billion cumulatively from 1950 due to extreme events, and that it has been losing $3 billion every year for the last 10 years.

This loss is now expected to increase as flood intensity increases. Last year’s floods in Kerala are expected to have cost the state roughly $6 billion.

Climate scientists have been increasingly interested in understanding the mechanism behind extreme events of rainfall. Their ability to predict severe rainfall has improved recently, but meteorologists have not been able to predict with accuracy the location of very heavy spells of rain. Last year, they expected Mumbai to experience heavy rain in mid-August, but rains lashed the southern part of the west coast instead of Mumbai.


In the paper in the journal Weather and Climate Extremes, Mishra and his colleagues at IIT-Gandhinagar show that multiday intense rainfall will also increase more than single-day intense rainfall. In another paper in the same journal, they say the frequency and severity of floods can be reduced if we cut carbon dioxide emissions. In fact, the severity of floods can be cut by half in the bestcase scenario for the century compared with the worst-case scenario, they add. The Intergovernmental Panel for Climate Change calls these scenarios Representative Concentration Pathway (RCP) 2.6 and RCP 8.5.

These scenarios do not directly correspond to average temperatures on earth, but is a combination of temperatures, economic growth and population. Under RCP 2.6, the best-case scenario, global emissions peak next year and decline to zero by 2080. Under RCP 8.5, the worst-case scenario, global emissions continue to rise throughout the century, along with a high population growth.

Under RCP 2.6, the global mean surface temperature is expected to rise by 0.3-1.7 degree Celsius by the middle or late 21st century. But under RCP 8.5 — if greenhouse gas emissions continue on a high trajectory — the temperature is expected to increase by 2.6-4.8 degree Celsius, leading to a higher degree of global warming and more extreme weather events.