No relief in sight: Northwest India to swelter till July, say experts

The north-western parts of India, which have suffered the most due to heatwaves in the past three months, may not get respite from the sweltering heat till July, according to experts.

One reason for this would be the ongoing westerly desert winds coming in from the Arabian Peninsula that usually cause heatwaves during the summer season in India, according to Raghu Murtugudde, a climate scientist at the University of Maryland, United States.

He highlighted that even though the usual heatwave season in India begins from May every year, the heatwaves this year are stronger in intensity than normal.

The monsoon winds have already set in over the Bay of Bengal, six days earlier than normal. But they will not be of much help.

“The south-westerly winds associated with the onset of the monsoon season turn eastward after 20 degrees north latitude and may not be able to disrupt the warm westerly winds causing the heatwaves just as yet,” said Murtugudde.

Another aspect is that the monsoon, even though early, may not bring good enough rainfall in its early days with intermittent rains and dry spells at the beginning, according to Elena Surovyatkina, a climate scientist and monsoon expert at the Potsdam Institute of Climate Impact Research in Germany.

This could lead to the continuation of the heat spells in some of the regions.

It’s burning

This is bad news as the heatwaves have been quite extensive and intense this season, with many places recording their hottest temperatures. Gurugram recorded a temperature of 48.1 degrees Celsius May 15, 2022, the highest since the formation of Haryana in 1966.

Since March 11, 16 Indian states and Union territories have suffered from heatwaves and a severe heatwave, according to an analysis done by Down To Earth, based on data from the India Meteorological Department (IMD).

The IMD says a heatwave happens when the temperature of a place crosses 40°C in the plains, 37°C in coastal areas and 30°C in the hills.

The weather agency declares a heatwave when a place registers a temperature that is 4.5 to 6.4°C more than the normal temperature for the region on that day for two consecutive days. If the temperature is over 6.4°C more than the normal, the IMD declares a ‘severe’ heatwave.

The IMD also uses another criteria to declare a heatwave which is based on absolute recorded temperatures. If the temperature crosses the 45°C mark, the Department declares a heatwave; when it crosses 47, a ‘severe’ heatwave is declared.

Rajasthan and Madhya Pradesh have suffered the most number of heatwave or severe heatwave days between March 11 and May 18 among the states and Union territories.

There have been 39 heatwave or severe heatwave days in Rajasthan. Madhya Pradesh came a close second at 38 days of heat.

The mountainous state of Himachal Pradesh, home to 2,500 glaciers, surprisingly suffered the third-highest number of heatwave or severe heatwave days at 27. It was ahead of states like Gujarat (25) and Haryana (23), which are usually heatwave-vulnerable states.

Even the Union territory of Jammu and Kashmir experienced 19 heatwave days in this period and Uttarakhand suffered from four heatwave days.

The heatwaves in the mountains are a cause of great concern as they could lead to accelerated melting of glaciers, forest fires, other weather-related catastrophes and impact on bio-diversity.

Soaring temperatures, combined with a complete lack of rainfall, led to a 30 per cent increase in forest fires in April in Uttarakhand as compared to the same period last year.

Early blooming has also been observed in the Valley of Flowers in Uttarakhand this year due to early heat. Himachal Pradesh also suffered from 645 forest fires in April, which led to the destruction of almost 5000 hectares of natural forests and plantations.

Also, people living in the mountains are not well-adapted to such extreme heat which they may need to start doing now.

“Buildings that are constructed with thermal comfort in mind. Walkable and green cities are important for adapting to such heatwaves,” Aditi Mukherji said.

Mukherji is principal researcher at the International Water Management Institute in Delhi and lead author of the Intergovernmental Panel on Climate Change’s Working Group II (WG II) report released in February 2022. The WG II report mainly deals with the impact of climate change and adaptation.

“But the caveat is that there are limits to these adaptations, and in cases like these, perhaps mitigation (reducing emissions) is the best adaptation,” she added.

Such extreme temperatures can have many unexpected and disastrous consequences. In Delhi, the heatwaves led to the Balswa landfill spontaneously catching fire on April 26 due to combustion of methane gas emanating out of the decaying organic matter.

This led to the capital city suffering from several days of extremely poor air quality. There had been two other landfill fires reported from the Ghazipur dumping site earlier.

March and April

The heatwaves this year have occurred too early and have struck with greater intensity.

“The unusual aspect this year was the early onset of the heatwave season and the duration, intensity and area covered during March and April. That was the combination of global warming and La Niña”, Murtugudde added.

The La Niña is the cooler-than-normal phase of the El Niño Southern Oscillation phenomenon in the equatorial Pacific Ocean that usually dissipates after the winter season in the northern hemisphere but has been quite adamant this year.

A pressure pattern associated with La Niña and its interaction with warm Arctic waves that resulted in the formation of anticyclones, was one of the reasons for the early onset and spread of heatwaves in March all across India. Anticyclones cause hot and dry weather by sinking winds around high pressure systems in the atmosphere.

In fact March 2022, which was the warmest March month in the last 122 years, recorded the highest heatwave and severe heatwave instances of 93 since 2010, said Mrutunjay Mohapatra, director-general of the IMD, as part of a press conference on April 30.

If a meteorological sub-division records a heatwave for one day, it is counted as one instance of heatwave, according to IMD.

April 2022, which was the fourth-warmest April month in the last 122 years, recorded the second-highest heatwave and severe heatwave instances of 146 between 2010 and 2022.

The highest was 404 in 2010. The month was especially drastic for northwest and central India which recorded their warmest April months in the last 122 years.

“The lack of rainfall in northwest India and central India in March and April was one of the causes for the continuity and intensity of heatwaves,” Mohapatra said.

The cumulative deficit in rainfall for northwest and central India between March 1 and April 28 was 87 per cent and 70 per cent respectively.

Mohapatra attributed this deficiency in rainfall to the lack of rain-bearing systems, especially western disturbances, which usually bring rainfall and cause thunderstorms in the regions in the pre-monsoon season.

Even though six western disturbances affected northwest India in April, they were feeble, dry and moved across the higher ridges of the Himalayas.

“Western disturbances in recent years have been causing less rainfall and moving across the higher ridges of the Himalayas, which could be a result of global warming,” AP Dimri, a scientist at the Indian Institute of Geomagnetism, Mumbai and an expert on western disturbances told Down To Earth.

Mohapatra had pointed out that the heatwaves may continue in northwest India in May as well, which has turned out to be true and they would likely continue in northwest India for the next couple of months.

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