The India Meteorological Department (IMD) issued a warning, on February 20, that the maximum temperatures in that week would be 3-5° C higher than the long-term average. The warning was issued for northwest, west, and central India.
The national capital recorded its second hottest February day (31.5° C) in the last five years, according to The Skymet Weather report. This is a shift from the normal weather trend as the "month of February starts with a normal of 23-degree celsius and closes with 25-26 degree celsius", the report said.
Speaking to BOOM, AVM Sharma, president (Meteorology & Climate Change) of Skymet Weather, said that this year the heatwave has come early against the normal trend. "We mostly recede the winters by February, but this time the shift has come early. Normally, the Indian Subcontinent experiences these waves in the pre-monsoon months, which are March, April, May and parts of June".
What are heatwaves and how do they occur?
The National Disaster Management Authority of India defines a heatwave as "a period of abnormally high temperatures, more than the normal maximum temperature that occurs during the summer season in the North-Western parts of India". People who live in these areas are impacted by the extreme temperatures and accompanying atmospheric conditions as they cause physiological stress, which can also result in death.
According to Sharma, the dry spell during pre-monsoon causes heat to accumulate which gives rise to the heatwaves. "Normally these dry spells are interrupted by the weather activities like rain, thunderstorm or hailstorms. In the absence of these phenomena, where the heat accumulates uninterrupted in the lower layers of the atmosphere, the pockets where these activities occur are pronounced as experiencing the heatwave", he said. Apart from northeast India and the coastal areas, the rest of India is susceptible to such conditions. Enumerating the states vulnerable to heatwaves, Sharma said, "Gujarat, Rajasthan, Odisha and interiors of the peninsula like Telangana and Andhra Pradesh, especially, experience such extreme conditions of weather."
Explaining the early arrival of heatwaves in India this year, Akshay Deoras, a research scientist at the National Centre for Atmospheric Science and the Department of Meteorology, University of Reading, UK, said, "The winds from the north-west push the heatwaves, originating in the Middle-East, towards India. Heatwaves need dry conditions for them to prevail and the absence of the western disturbances in northern India provides the apt scenario. And last year, there were no substantial western disturbances, in the month of November and December."
What effects do the El Nino and La Nina currents have on heatwaves?
According to Sharma El Nino and La Nina are ocean-borne phenomena and are inverse of each other. The sea surface temperature in the Pacific Ocean dictates their formation. He said, "The warming of sea surface temperature in the equatorial Pacific region by more than 0.5 degree celsius, in a persistent fashion causes the El Nino situation. The opposite of this situation, which is the dropping of sea surface temperature by a similar margin, causes the La Nina situation. These climate patterns in the Pacific Ocean are capable of affecting weather worldwide."
Speaking to BOOM, Deoras said, the last three years have been La Nina years, while 2023 is likely to be an El Nino year. Explaining further about the phenomenon, he said that "Each effect lasts mostly a year, as they alternate between each other, but sometimes they may last more than a year or two". The El Nino effect will impact the southwest monsoon and northeast monsoon in India. It will increase the severity and magnitude of the heatwaves, Deoras added.
How can heatwaves affect India's economy?
Heatwaves in India can impact the economy because weather has a significant impact on agriculture. Around two-thirds of India's population is dependent on agriculture for a living.
According to Sharma, any weather condition which shifts from normal will impact crop production, be it rabi or kharif. The crops that are sown in the rainy season are called kharif crops (also known as the summer or monsoon crops) in India. Kharif crops are usually sown with the beginning of the first rains in July. The crops that are sown in the winter season are called rabi crops (also known as the winter crop). They are grown within the period of November to April.
Deoras said that the prevailing conditions were of concern as the winter season is shrinking and the summer season is being prolonged. This, he said, would affect sowing and reaping patterns in the agricultural sector. "As this would be an El Nino year and the monsoon forecast is not that promising, this will affect the sowing of kharif crops. Hence, the output will not be as expected", he said.
Elaborating on the effect of a heatwave on employment, Deoras explained, "If we receive acute rainfall, especially in the key agriculture states of India, the employment rate will see a significant impact. As the crop output decreases, the profit margin will decrease which will lead to lesser people being employed on the fields. This would be a worse-case scenario but we cannot strike out its possibility."
Heatwaves also impact labour productivity. According to a report by International Labour Organisation, labour productivity in the agriculture and construction sector will be the worst impacted during the heatwave. The country most affected by heat stress is India, which lost 4.3 per cent of working hours in 1995 and is projected to lose 5.8 per cent of working hours in 2030. Moreover, because of its large population, India is in absolute terms expected to lose the equivalent of 34 million full-time jobs in 2030 as a result of heat stress, the report read.