Climate change likely raises risks of brutal heatwaves by 30 times

Heatwaves such as the brutally long one over parts of India and Pakistan this year, which has claimed 90 lives so far and resulted in crippling power shortages and reduced crop yields, are about 30 times more likely due to human-induced climate change.

This was the finding of a study released on Monday by an international team of 29 climate scientists under the World Weather Attribution (WWA) group.

Their analysis showed an event like the current heatwave is rare, with the probability of one occurring once every 100 years, but also revealed that human-induced climate change since the pre-industrial era has made it about 30 times more likely, implying it would have been "extraordinarily rare", a one-in-3,000 years event, without the impact of climate change.

To understand how climate change would impact the long-running spell of high temperatures in India and Pakistan, the scientists used data from the region and computer simulations to compare the climate as it is today, factoring in a 1.2 deg C global warming since the late 1800s, with the climate of the past.

Large parts of India and Pakistan have been experiencing an unusually long heatwave this year, which has been worsened by the lack of pre-monsoon rainfall. It began as early as March, the hottest ever since India began keeping temperature records in 1901, and intensified last month. Heatwaves occur mostly from April to June, but peak temperatures of over 45 deg C were recorded in many parts of India in April, which was the third-hottest in 122 years.

Temperatures have soared to record levels in Pakistan; on May 14, Jacobabad was one of the hottest cities on earth at 51 deg C. Minister for Climate Change Sherry Rehman described this year as a "spring-less" year for Pakistan, with reports of many people being forced to drink contaminated water because of a water shortage due to the prolonged dry period.

India's capital Delhi is also having a water shortage with the Yamuna River "almost dry".

Professor Krishna AchutaRao from the Centre for Atmospheric Sciences at the Indian Institute of Technology Delhi, who was involved in the study, told a WWA media briefing on Monday that a 2 deg C rise in temperature would make an event like this year's heatwave "anywhere between two and 20 times more probable". He added: "It would be between half a degree and 1½ degrees warmer compared to what we have seen in this 2022 event."

The study follows a report last week by Britain's national weather service that found the record-breaking heatwaves in India and Pakistan have been made 100 times more likely by the climate crisis.

Those associated with the WWA study said their findings were "probably on the conservative side" and linked their lower estimates to various factors, including the fact that they studied a different region in India and Pakistan. "The real result is probably somewhere between ours and the Met Office result," said Dr Friederike Otto, a senior lecturer in Climate Science at Imperial College London and WWA's co-lead.

Meanwhile, parts of north-east India and Bangladesh continue to reel under intense rainfall and crippling floods. Dr Roxy Mathew Koll, a climate scientist at the Indian Institute of Tropical Meteorology in Pune, said episodes of extreme rain that cause flooding in India have tripled during the last few decades along with Arabian Sea cyclones that have increased by more than 50 per cent. "The pace of warming is now so accelerated that we need urgent action at global levels. Our climate action plans should be aligned to this near-future that we are living through. Unfortunately, they are not," he said.