The science

The World Weather Attribution (WWA) network, a global collaboration of leading climate scientists who work on analysing whether a particular extreme weather event is linked to the climate crisis, will submit findings of their study on this year’s spring heatwave in India and Pakistan (in March and April) within the next fortnight.

WWA scientists Sarah Kew and Robert Vautard said during a recent workshop that there is only a one in a 100 chance of such a heatwave occurring every year, stressing that the event was rare because of the very large area that was affected ; the long duration of the heatwave spell; and very early onset of the heatwave during the spring season. The scientists said the spell affected all of northwest India, central India and even parts of east India. Vautard said even though the 2022 heatwave was unusual with return period of the order of 100 years, such events are occurring more often and its alright to expect unbelievable extreme weather events.

“The temperatures that formerly constituted ‘extreme’ are now just unusual. And temperatures which were previously all but impossible are the new definition of extreme. Crucially, the change of likelihood happens fastest for the most extreme temperatures…an increase of 1ºC in global temperature therefore makes heatwaves more than 1ºC hotter,” WWA said in a recent guide last week on ‘Reporting extreme weather and climate change.’ WWA cited an Intergovernmental Panel on Climate Change (IPCC) report from 2021 that said a heatwave that would have occurred once in 10 years in the pre-industrial climate will now occur 2.8 times over ten years and be 1.2°C hotter. At 2°C of global warming, it will occur 5.6 times and be 2.6°C hotter. Similarly, a heatwave that would have occurred once in 50 years in the pre-industrial climate will now occur 4.8 times over 50 years and be 1.2°C hotter. At 2°C of global warming, it will occur 13.9 times and be 2.7°C hotter.