Heat waves in India may signal changing climate

Posted: 22 May 2009

India is being hit by more intense and longer heat waves that are taking a higher toll than usual on lives and the environment, says a report in the latest issue of Down to Earth magazine. Could this be another signal that climate change is aleady impacting the country, it asks.

In March-April, over 70 people reportedly died in Orissa due to sunstroke, with mercury soaring to 46 degree centigrade in April in some cities. The state's health machinery was caught napping. In West Bengal, the heat wave killed nine. 'Abnormal' dry spells and dust storms swamped Guwahati in Assam, while the entire Malwa region in Madhya Pradesh reeled from a severe water stress.

Sunstroke deaths in Orissa
Sunstroke deaths in Orissa
Khurda is the worst affected district in Orissa, with 10 sunstroke deaths reported. Photo: Agnimirh Basu
What is wrong with the weather, asks the report. According to the Indian Meteorological Department (IMD), disturbances in the air circulation pattern over India led to mercury soaring across the country. Circulation of air helps distribute heat over the earth. The cyclonic storm, Bijli, which formed in the Bay of Bengal in mid-April, cut off the cool easterly winds blowing in from the Bay of Bengal. To add to it, an anticyclone hovering around Rajasthan blew hot winds from north-west to central and western India.

Some scientists have attributed the heat wave to an exceedingly dry winter, while others have pointed to the unusual heating of the Tibetan Plateau - which was two degrees warmer than normal in February this year.

The IMD also points to the lack of winter cyclones that form in Bay of Bengal and provide rains to the north-east, as a reason. The Down To Earth report quotes A K Srivastava, a scientist at the department's Pune centre: "Tropical cyclones in the peak cyclone months of May and November have increased, while those occurring in the rest of the year have decreased."

Earlier warming An IMD study has compared the number, duration and spread of heat waves from 1971 to 2000 recorded in 35 sub-divisions across the country. The study says that on average, almost 23 of these areas were hit by heat waves between 1991 and 2000, while 10 sub-divisions were hit in 1981-1990 and only about 7 were hit in 1971-1980.

The study also says that 25 sub-divisions went through more than 15 spells of heat waves in 1991-2000, compared to only two in the previous two decades. Notably, the decade 1991-2000 has been the warmest in the last 140 years.

Meteorological data shows that March and April have been warming faster in the last 100 years. The average temperature for March has increased by 0.76 degree centigrade over the last century; that for April has increased by 0.58 degree centigrade.

"While governments sleep over these very visible trends, more intense and longer heat waves are taking a higher toll. Is climate change more imminent than thought of? the magazine asks.

Down to Earth is published by the Centre for Science and the Environment in Delhi. The full cover story may be seen at www.downtoearth.org