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Mint Primer | Into the 50s: Why heatwaves are hotter & longer
Summary
- For most of April, India saw heatwave or ‘severe heatwave’ conditions, and it’s continuing in May as well. Central, North and Peninsular India has borne the brunt of it
At 2.30pm on Wednesday, the NCR’s temperature hit a shocking 52.3 degrees Celsius, its hottest day ever, according to a screenshot taken by Mint. Earth sciences minister Kiren Rijuju later said this was “not official yet" and described such a high temperature as “very unlikely" while asking the weather office to verify the report. Nonetheless, extreme hot weather is increasing both in duration and intensity. Mint takes a look at heatwaves, what causes them and how prepared we are to deal with this weather event.
How severe has the heatwave been?
For most of April, India saw heatwave or ‘severe heatwave’ conditions, and it’s continuing in May as well. Central, North and Peninsular India has borne the brunt of it. Worst hit were Rajasthan, Punjab, Haryana, Delhi, Uttar Pradesh, Chhattisgarh, Odisha, Karnataka, Andhra Pradesh, Telangana and Tamil Nadu. Even Kerala and Sikkim which were not part of the heatwave zone have started experiencing it. Recent studies show humidity levels have risen significantly, and night-time cooling has moderated. Both these factors have increased the intensity of the heatwave.
What is causing these heatwaves?
Experts point to two factors. El Nino, a weather pattern that causes abnormal warming of waters in the equatorial Pacific Ocean, typically leads to heatwaves and extreme heat weather conditions across many parts of the world. The year 2024 began with strong El Nino conditions. The second is the presence of high-pressure systems over the Southern peninsula and South-Eastern coastal areas. These high-push warm air close to the Earth’s surface, adding to the heat. They also prevent incoming sea breeze that cools the land. This explains why night-time cooling has been to a lower scale than before.
Also read: Delhi's power demand soars as temperature hits new high
When is a heatwave declared?
Not all hot days are heatwaves. The weather office declares a heatwave if the temperature exceeds 40°C or is 4.5°C above normal in the plains. In coastal region it is 37°C or 4.5°C above normal. At least two weather stations in a sub-division must record this temperature for two consecutive days. For a severe heatwave, the mercury must be 6°C above normal.
Are they getting harsher and longer?
Yes, they are. Earlier, heatwaves used to last four to eight days. Now they last for 20 days. In the last two years alone, India has seen an unprecedented 328 heatwave days. And 2023 was the hottest year on record. Experts attribute all this to climate change, which increases the intensity and frequency of extreme weather events. The hot weather is taking its toll on humans too. Anecdotally, many are dying from it but the absence of nation-wide data on heatwave deaths means policy response has been behind the curve.
What more needs to be done ?
India’s first heatwave action plan was developed three years after a heatwave claimed 800 lives in Ahmedabad in May 2010. It involved setting up an early warning system, improving the healthcare system and creating awareness. Many states now have action plans. But experts suggest redefining the criteria for a heatwave, factoring in humidity, tailoring it for local conditions and making it available at district level. Local information about heatwave intensity will help officials take better pre-emptive actions.
