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Heatwave occurrences increasing in India, occurring in new regions: study

Recent analysis by the Center of Excellence in Climate Change Research. The Mahamanas (MCECCR) of Banaras Indian University (BHU), in collaboration with the Department of Science and Technology and the Ministry of Earth Sciences, discovered a spatial shift in heat waves in India, now occurring in new regions of the country.

Heatwaves are defined as prolonged episodes of extreme temperatures in any region. In addition to temperature, humidity is an important parameter taken into account when declaring heat stress.


Links to rising mortality

The presence of humidity in the environment interferes with the thermoregulatory mechanism of evaporative cooling of the body through perspiration, which can cause heat stress. A 0.5 degree Celsius rise in average summer temperatures could cause an increase in heat deaths from 2.5 to 32% and an increase in heatwave duration from 6 to 8 days and lead to a 78% increase in the probability of death.

The MCECCR study looked at temperature data for the pre-monsoon seasons (March-May) and early summer monsoons (June-July) from the Indian Meteorological Department over 65 years from 1951-2016 to estimate monthly, seasonal, decadal and long-term trends abnormal heat in the country. There is a warming trend over the north-west and south of India and a gradual cooling over the north-east and south-west regions of the country.

The study found a “space-time shift” in heat waves with a significant upward trend in the three most heat-prone regions – northwest, central and south-central India, with the highest in west Madhya Pradesh (0 , 80 events / year).

“Heat waves are traditionally associated with UP, Bihar, Delhi and the northern parts of Madhya Pradesh. For the study, we analyzed daytime temperatures on a 0.25 square kilometer grid over the past seven decades. Both heatwaves and intense heat waves are on the increase – and we are finding new places where these phenomena occur, especially in the past two decades. We have detected heatwaves in the southern states of Madhya Pradesh, Andhra Pradesh, Karnataka and Tamil Nadu, where they traditionally would not have occurred, ”said Rajesh Mall BHU, lead author of the study, along with scientists Somya Singh and Nidhi Singh.

Moll said that the increase in heat waves in Karnataka and Tamil Nadu is particularly significant and indicates an increase in the number of events in the future.

Interestingly, the study also found a significant decrease in heat waves in the eastern region, that is, in Gangetic West Bengal (-0.13 events / year).

Over the past several decades, heatwaves have occurred in southern states that have not experienced such phenomena before. The study says that particularly intense heat waves showed “southward expansion and spatial surge over the decades 2001–2010 and 2010–2016.”

In the period 1961–2010, March to July, the northwestern, northern, central and eastern coastal regions accounted for the largest number of heat wave days, with an average of eight days with anomalous weather and 1-3 days with strong weather during season. …

Two elements that have exacerbated the country’s heat wave conditions are an increase in temperature at night, which inhibits heat dissipation at night, and an increase in humidity.

“During the decade 2001–2010. There has been an upward trend in the number of days with heat waves and days with heavy weather compared to previous decades, ”the study said, adding that the east and west coasts, which are currently not affected by heat waves, will be severely affected. in future.

In addition, the analysis found a jump in heat-related deaths from 5,330 deaths recorded in 1978-1999 to the extreme deaths of 3,054 and 2,248 in 2003 and 2015, respectively.



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