Heat waves across India rose over 50 years, more to come

MUMBAI: Heat waves across the country have increased in the past 50 years, by more than 31%. What’s more? India must brace itself for more next year, if the current El Nino conditions persist in the Pacific Ocean.

Heat or severe heat waves occur when excessively hot weather, beyond the threshold temperature of a region, lasts for a prolonged period. This could be coupled with high humidity.

According t o an analysis by India Meteorological Department (IMD), Pune, more than half the number of weather stations — 57 of 103 — across the country recorded heat waves in summer for an average of 550 days, between 1961 and 2010.

Similarly, severe heat waves were observed for an average of 60 days, with 18 stations being the most affected over the five decades.

Interestingly, most long spells of heat and severe heat waves were recorded in the years that follow an El Nino year — when surface ocean waters in the eastern and central tropical Pacific Ocean are abnormally warmed.

“Natural and manmade activities, along with climate change, lead to an increase in land surface air temperature. This means we will see a rise in extreme events, including heat and severe heat waves in the country,” said scientist DS Pai, National Climate Centre, IMD Pune. Pai said states such as Rajasthan are already witnessing a rise in heat wave conditions.

In 2014, Maharashtra, Punjab, Haryana, Delhi, Uttar Pradesh, Rajasthan, Gujarat, Odisha and Bihar were hit by heat waves, with temperatures reaching 45 degree Celsius. With Nellore in Andhra Pradesh being most prone, the north, northwest, central and northeast, on an average, witnessed more than 8-15 heat wave days.

Severe heat waves were experienced in the northwest, north and eastern parts for one to three days, and sometimes extending beyond a week.

Following the three El Nino years of 2002, 2004 and 2009 in the last decade, which was also the warmest since 1880 globally and since 1901 for India, the number of heat wave days significantly increased to an of average 670 days per year from 2001-2010, compared with 580 days per year between 1991 and 2000.

In contrast, an average of 510 heat wave days was recorded annually during the 1961-1970 and 1971-1980 decades. There was a slight dip to 470 days per year, from 1981-1990.

Similarly, severe heat waves days hitting various parts of the country almost doubled, to an average 98 days every year from 2001 to 2010 as compared with 48 days per year in the previous decade.

Further, more lives were claimed by heat waves in the years following El Nino (1983, 1988, 1995, 1998, 2003, 2005 and 2010).

More than 1,000 people died because of a heat wave in May 2002 in Andhra Pradesh and around 200 people died across the country. In May 2010, more than 250 people died in north India.

“We need proper early warning systems, improvement in public information campaigns on the dangers of heat waves and the use of social care networks to reach vulnerable sections of the population,” Pai said.