May 23, 2022 - Energy & Environment

Study: Climate change made India, Pakistan heat wave 30 times more likely

A villager walking through the cracked bottom of a dried-out pond on a hot summer day at Bandai village, India.

Shivaram, a villager walking through the cracked bottom of a dried-out pond on a hot summer day at Bandai village in Pali district, India, during a heat wave on May 11, 2022. Photo: Prakash Singh/AFP via Getty Images

Human-caused climate change has ratcheted up the odds and severity of the record-shattering heat wave that has gripped India and Pakistan since March, a new study finds.

Why it matters: The climate attribution study is the first to specifically examine the factors behind the 2022 heat wave. The new work also indicates that heat waves worsened by global warming are affecting human health, food security and economic output.

  • A separate study that was published earlier this month examined the odds that a heat wave would break a record set in 2010.

Driving the news: Since March, India and Pakistan have seen extraordinarily high temperatures and below average rainfall. The dry conditions have only raised temperatures further, hampering economic activity by cutting down on outdoor work. The heat wave has killed at least 90 people, the study states.

  • March was the hottest month in India since records began there 122 years ago, the study notes, and Pakistan set the highest worldwide positive temperature anomaly during for the month. The heat continued during April and into May. On April 29, the study finds, 70% of India was enveloped by the heat wave.
  • Temperatures in the hottest locations have routinely reached or exceeded 120°F.

The big picture: While extreme heat is common in India and Pakistan prior to the onset of the summer monsoon, the hot weather this year has been unusually pronounced, as well as longer-lasting than usual. It also hit earlier in the year than is typically seen.

  • The heat has dented wheat crop yields at a time when global supplies are strained due to Russia's invasion of Ukraine, prompting India to cut off exports to the global market.
  • It also produced a damaging glacial lake outburst flood in northern Pakistan.
  • "Climate change is fueling impacts that ripple across to other parts of the world, not just the face where the heatwave is occurring," said study coauthor Roop Singh from the Red Cross Red Crescent Climate Center.

Zoom in: The study was conducted by more than two-dozen scientists around the world who are affiliated with the World Weather Attribution project, which uses peer reviewed methods to conduct rapid analyses of how climate change has influenced an extreme weather event.

  • They examined the average of daily maximum high temperatures during the March through April 2022 period.
  • The researchers concluded that the heat wave has been about a 1-in-100-year event in this region, although they caution this is likely an underestimate due to a relatively short period of data in some areas.
  • The study found that human emissions of greenhouse gases made this event both about 1°C hotter and more likely to occur, with the probability of such an event increasing by a factor of 30.

Threat level: If global average temperatures reach 2°C above preindustrial levels, such a heat wave would become an additional 2% to 20% more likely, and up to 1.5°C hotter than the 2022 event, the study found. This mean such heat waves could have a typical return period of once every five years in such a warming scenario.

  • This is a noteworthy finding since currently, the world is on course for about 3°C of warming by the end of the century.

Yes, but: The researchers note that measures can be taken to help protect vulnerable populations from such events, such as heat wave early warning systems and bolstering public services such as cooling centers.

What they're saying: "[In] a world without climate change, this event was highly, highly unlikely," said Arpita Mondal, a study co-author from the Indian Institute of Technology Mumbai, on a conference call with reporters.

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