Climate Change

Intensity, extent and duration of severe heat waves to increase dramatically: study

The entire stretch from Uttar Pradesh in the north to the southern peninsular tip is likely to be badly affected by increased heat wave frequency

 
By Shreeshan Venkatesh
Last Updated: Tuesday 17 October 2017
The frequency of heat waves will increase by 3-9 events in the next 30 years. Credit: Vikas Choudhary / CSE
The frequency of heat waves will increase by 3-9 events in the next 30 years. Credit: Vikas Choudhary / CSE The frequency of heat waves will increase by 3-9 events in the next 30 years. Credit: Vikas Choudhary / CSE

A study published in the journal Environmental Research Letters on October 16, for the first time, gives us an estimate of the human impact of increasing frequency of heat waves as we proceed into the 21st century. The study reveals that under a business-as-usual scenario regarding emissions, frequency of heat waves could increase by about 75 times. Adherence to the Paris Agreement and limiting global mean temperature rise below 2 degrees may cause a 30-fold increase in severe heat wave frequency by the end of the century. By 2100, the population affected under an unhindered emissions scenario could be as much as 200 times the current affected population, according to the study.

Findings on increased frequency of heat wave

Under the current emissions scenario, the study shows that the entire stretch from Uttar Pradesh in the north to the southern peninsular tip is likely to be badly affected by the increase in heat wave frequency. In comparison to heat wave frequency between 1971 and 2000, authors estimate that the frequency will increase by 3-9 events in the next 30 years. This increase is projected to be as high as 18-30 events by the final quarter of the century.

Researchers used multiple climate models and heat wave frequency between 1971 and 2000 as a reference to illustrate the difference in heat wave frequency, duration and distribution between different scenarios for both mid- and end-century time frames. Dependent on daily magnitudes of heat waves (dependent on temperature profiles of individual places on the days of the heat waves), researchers create a benchmark for “severe heat waves”.

The study finds that intensity, spatial coverage and duration of severe heat waves are set to increase dramatically, affecting a larger population in the coming decades. Reduction of emissions to limit warming under 1.5 degrees is found to be the only scenario where disaster risk mitigation need not be taken at a war-footing to combat heat waves in the country.

While the population affected does represent the largest group as it does not consider the effects of overhead structures or personal coping mechanisms that may be employed to tackle heat waves. At the same time, the intensity of heat waves is also likely underestimated as the formulations used in the paper rely purely on maximum temperatures to define and categorise heat waves, whereas, the effect of heat on human bodies is greatly influenced by other environmental and atmospheric conditions such as relative humidity. According to the authors, their effort to include the same was scuttled by the lack of long-term data about these meteorological factors.

This new study comes quick on the heels of another study published in August this year that claimed that heat waves in South Asia by the end of the century could surpass the limits of human survivability if current emission levels continue.

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