Explainer: Why heatwaves are the new normal in India, and how they impact us

As per the National Disaster Management Authority, a heatwave is a period of abnormally high temperatures, more than the normal maximum temperature that occurs during the summer season. In India, the IMD typically issues a heatwave alert if the maximum temperature of a station reaches at least 40 degrees Celsius or more in the plains, and at least 30 degrees Celsius or more for hilly regions.

While heatwaves are common in central and northwest India, climate change, due to global warming, has exacerbated their effects. Daily peak temperatures are now higher and heatwaves occur more often, growing longer in duration and more intense with each passing year.

2022, for instance, was one of the hottest summers on record. The country recorded 203 heatwave days, the highest in the recent past, as per data shared by the Ministry of Earth Sciences in the Lok Sabha. While Uttarakhand reported the highest number of heatwave days (28), Rajasthan (26), and Punjab and Haryana (24 each) closely followed.

This year, western disturbances, which play a key role in controlling temperatures in northwest and central India, were less intense in February. It led to temperatures rising faster than normal. A very early and strong anti-cyclonic circulation also dominated the atmosphere over India and resulted in one of the earliest 40 degrees Celsius maximum in the country. And with the possibility of the El Nino weather phenomenon disturbing the monsoon rains this year, the summer of 2023 too could be hot, intense, and dry.

Whom does it impact?

A report by the World Bank in 2022 has stated that India will soon be one of the first countries to experience severe heatwaves that will break the human survivability limit. While heatwaves impact everyone, their effects are often worse in cities. Buildings, roads, and infrastructure absorb and retain heat, and drive up temperatures (a phenomenon known as the urban heat island effect).

Already, as per a study published in the medical journal The Lancet, the country has seen a 55 percent rise in deaths due to extreme heat between 2000-04 and 2017-21. It has caused a loss of 167.2 billion potential labour hours among Indians in 2021 and resulted in loss of incomes equivalent to about 5.4 percent of the country's GDP.

In 2022, Wildlife SOS treated over 300 birds for conditions such as fever, dehydration and heatstroke as temperatures crossed 46 degree Celsius in Delhi-NCR. (Representational image: Anshul Sharma via Wikimedia Commons)

Heatwaves also have a deep impact on the environment

Tree damage and drying of landscape: Without the naturally accompanying increase in precipitation, heatwaves lead to water shortages and increase stress for plants, especially in arid areas. It can reduce plant growth and lead to overall drying of the landscape. For instance, the 2003 heatwave in Europe caused tree damage, increased leaf fall and degraded carbon sinks, resulting in more CO2 being released into the atmosphere.

Increased forest fires: Hot and dry conditions lead to the start and rapid spread of forest fires. The damage by wildfires in Uttarakhand, for example, has more than tripled in just four years. In 2017, 1,244 hectares of forest burned in the hill state, while it reached 3,927 hectares in 2021. Since January this year, over 107 hectares of forest cover has already been affected by wildfires due to the hot weather, as per data from the state's forest department.

Melting of glaciers: Shallow aquatic ecosystems dry up and glaciers melt. For instance, as per the United Nations Development Programme, temperatures in the Himalayas are rising twice as fast as the global average, melting ice and cutting snowfall. If this goes on, between half and two-thirds of the total ice mass will disappear by the end of the century.

Wildlife: Blistering heatwaves have a devastating impact on animals and birds too. In 2022, Wildlife SOS treated over 300 birds for conditions such as fever, dehydration and heatstroke as temperatures crossed 46 degree Celsius in Delhi-NCR. Severe water shortages can also impact the daily life of animals, and affect their breeding and migration patterns. For animals such as the snow leopard, a gradually shifting treeline due to rising temperatures can mean loss of habitat and fewer opportunities to hunt prey, threatening their very existence. Changing climate conditions due to heatwaves can also cause invasive alien species to spread and thrive, thus impacting biodiversity.

Other challenges: Heatwaves also affect the agricultural industry by threatening crop yields, affect cold chain infrastructure, and increase power consumption, which hinges on coal (a fossil fuel that accounts for more than 55 percent of India’s energy needs).

What can we do?

While we cannot stop heatwaves, we can reduce their negative impacts by mitigating climate change. One effective way to do so is by reducing greenhouse gas emissions and minimising the rise in global mean temperatures by going net-zero.

Governments also need to create early warning systems to build resilience among communities and save lives. To this end, Prime Minister Narendra Modi chaired a high-level meeting recently to review the country’s readiness for “hot weather” in summer. Officials were directed to sensitise children on dealing with extreme heat, and release daily weather forecasts that can be easily interpreted and disseminated.

Lastly, there needs to be a growing focus on sustainable planning to boost green spaces and other cool environments around the country, which can help in reducing surface temperatures and provide nature-related benefits. Only then, perhaps, we may be able to beat the heat.