“What was particularly exceptional and particularly unusual was how early it started,” Friederike Otto, co-author of the study, said at a press conference on Monday.
India experienced its highest March temperatures in 122 years, and Pakistan and northwest and central India experienced their hottest April. Many historical and monthly temperature records were broken in both countries. Over the two months, extreme heat affected almost 70% of India and 30% of Pakistan.
This heat event would have been “highly, highly unlikely” in a world without climate change, said Arpita Mondal, co-author and professor at the Indian Institute of Technology Bombay.
The heat has had a huge impact on people across the region. Workers were no longer able to work full days outdoors, straining their livelihoods and the economy. India’s main farming areas are expected to see a 10-35% drop in crop yields due to the heatwave, pushing up local market prices and reducing global wheat supplies at a time when supplies are tight. already under pressure due to Russia’s invasion of Ukraine. Hundreds of wildfires have also burned across India. In Pakistan, melting snow has flooded a glacial lake and destroyed a key bridge.
In both countries, at least 90 deaths have been heat-related.
The analysis was carried out by the group Global Weather Allocation, which uses computer modeling to study the links between ongoing weather events and climate change. The team ran simulations using 20 different models with and without the effects of human-induced climate change to determine the effect of rising temperatures on the magnitude of the heat. The results, which have yet to be peer-reviewed, come from well-established methodologies that have been used in previous analyses, including one conducted on the 2021 Pacific Northwest heat wave.
Otto said the study’s estimate of the effect of climate change is conservative due to data constraints and that rising temperatures likely increased the likelihood of the event “over 30 times”.
The study was published five days after a similar analysis by the UK Met Office. He revealed that a record April and May in northwest India and Pakistan have become about 100 times more likely due to climate change. Otto said the Met Office estimate was well within the uncertainty range of the latest study.
“Both show that climate change is really a game-changer when it comes to these kinds of heat waves,” Otto said. “The main take-home message here [is] that adapting to the heat has been the absolutely essential thing to do in life in all parts of the world, really, but especially also in this part of the world.
The World Weather Attribution study also looked at the likelihood of a heat wave similar to this year’s occurring in an even warmer world. The team found that such a heat wave would become two to 20 times more likely if the planet reached 3.6 degrees (two degrees Celsius) above pre-industrial levels.
India has warmed by about 1.8 degrees (one degree Celsius) since pre-industrial times. Pakistan warmed by 2.2 degrees (1.2 degrees Celsius).
The study adds to growing research that highlights how climate change is increasing extreme weather events across the globe. According to the climate report released by the United Nations last year, evidence shows that heat waves have increased in almost all land regions due to climate change.
“We studied many heat waves, and in all but one case, climate change was clearly assessed as the main driver of the change in probability,” said Robert Vautard, director of the Pierre-Simon Laplace Institute in France. France and co-author of several studies with World Weather Attribution.
Northern India and Pakistan face another heat wave later this week. After relatively cool weather over the next few days, temperatures are expected to rise several degrees above average on Friday into the weekend.
