After its hottest February since 1901, the India Meteorological Department has issued an early heatwave warning and forecasts for higher than normal temperatures between March and May.
We asked Kieran Hunt, a climate scientist at the National Centre for Atmospheric Science and University of Reading, to explain how El Niño and climate change are bringing soaring temperatures to India.
Heatwaves are periods of abnormally hot weather, usually lasting several days. They pose a danger to life, disrupt infrastructure and travel, and can significantly affect employment and crop output in the agriculture sector of countries like India. The global rise in temperatures, from human-induced climate change, means that heatwaves are occurring against a warmer background and so are more frequent and more extreme.
Reports from the Intergovernmental Panel on Climate Change share compelling evidence that with every degree of additional warming to the world’s climate, the frequency and intensity of heatwaves are projected to get worse in future.
The average temperature at the Earth’s surface has risen by about 1°C since the pre-industrial period, which is a rate unprecedented in the history of human civilisation. And while that temperature change may not seem rapid, it has meant 17 of the 18 warmest years on record have occurred in the 21st century.
In the next three decades, record-shattering heatwaves could become two to seven times more frequent across the world than in the last 30 years. Beyond 2050, if global greenhouse gas emissions continue to rise, hazardous hot spells could be three to 21 times more frequent. At present warming levels, India sees about 12 days per year with extreme heat (greater than 47°C). This is expected to rise to about 18 if global warming reaches 1.5°C; and to about 30 if global temperatures reach 2°C above pre-industrial conditions.
Heatwaves need dry and clear conditions for them to prevail. Hot, dry air comes to India from the Middle East and combines with extra solar heating from the lack of clouds, leading to conditions that are apt for heatwaves. In the last few months, there has been a lack of winter storms in that part of the world – known as western disturbances – that would normally disturb any growing warm spells.
Kieran Hunt adds:
The last three years have been dominated by La Niña, a global weather phenomenon that sees cooling of the sea surface in the Pacific Ocean with knock-on effects for worldwide circulation of air and weather. In 2023, El Niño is set to return, bringing with it contrasting conditions. With persistent warming of the sea surface in the equatorial Pacific region, El Niño impacts India by causing reduced cloud cover and below-normal rains, often leading to drought and severe heatwaves, followed by a disrupted monsoon season. The highest temperature ever recorded in India was 51°C, which occurred during the strong 2016 El Niño.
Kieran follows with:
People in India suffered devastating heatwaves between March and April in 2022, with temperatures soaring 8°C higher than the average for that time of year. The country experienced five times the number of heatwave days in the early summer of 2022 than it did during the same season of 2021. It’s not known what the severity and magnitude of heatwaves in India will be during 2023, but the warning signs are here.
The weather conditions in India are not only a concern for risk to life, but also livelihoods. Heatwaves affect sowing and reaping patterns in the agricultural sector, which has significant impacts on employment rate, labour productivity, and global food supplies.
These heatwaves shorten the spring crop season. If crop output decreases, the profit margin will decrease, leading to fewer people being employed on the fields. Labour productivity is the worst impacted during heatwaves, especially as India is the country most affected by heat stress. This is why heatwaves also put additional pressure on the global food market, given India is one of the world’s biggest producers of wheat.
Scientists like Kieran Hunt at the National Centre for Atmospheric Science investigate how heatwaves, and other types of severe weather, are caused by air circulation patterns in our atmosphere and human-induced climate change. They study how these patterns develop, how to predict them, and how climate change will impact our weather.
Their approach uses a combination of computer simulations of the atmosphere, long-term measurements collected from around the world, and new tools for characterising the properties of the atmosphere.