Global heating to date of 1.2 degrees Celsius has shortened the so-called return period for the extreme heat of similar duration and intensity in South Asia to once a century, experts say in report.
The punishing heatwave that scorched India and Pakistan in March and April has been made 30 times more likely by the climate crisis, experts in quantifying the impact of global heating on extreme weather events said in a rapid-response report.
Before the onset of the human-caused climate crisis, the chances of such an event occurring would have been roughly once every 3,000 years, senior author Friederike Otto, a scientist at Imperial College London’s Grantham Institute, told the AFP news agency.
Global heating to date of 1.2 degrees Celsius has shortened the so-called return period for the extreme heat of similar duration and intensity in South Asia to once a century, she and colleagues in the World Weather Attribution (WWA) consortium found.
But as the planet continues to heat up, the interval between such killer heatwaves will shrink even further.
If Earth's average surface temperature rises another four-fifths of a degree to 2C above preindustrial levels, "a heatwave like this one would be expected as often as once every five years", they concluded.
The March-April period was the hottest on record for that time of year in Pakistan and India.
It will be months before the full toll of lives lost and economic damage can be calculated, including hospitalisations, lost wages, missed school days, and diminished working hours.
More than 90 deaths have been directly attributed to the heatwave, but earlier hot spells over the last decade suggest that number will climb far higher, perhaps into the thousands.
Agricultural disaster in India
One impact was immediate.
The withering heat combined with 60 to 70 percent less rain than usual turned what promised to be a bumper wheat crop in India into an agricultural disaster.
As a consequence, India last week blocked millions of tonnes earmarked for sale abroad, pushing up global prices already hit hard by conflict-torn Ukraine's crippled wheat exports.
The unprecedented duration of the heatwave, which saw power outages as temperatures soared into the high 40s, suggests climate-vulnerable countries are racing against the clock to prepare for a climate-addled future, the report said.
Already today, "the limits to adaptation are being breached for a large, poor population of the region," cautioned Islamabad-based climate scientist and co-author Fahad Saeed.
"One can imagine how bad it would be even for a 1.5C-warmer world," he said, referring to the aspirational Paris treaty target for capping the rise in global temperatures.
Any warming beyond 1.5C, he added, would pose an "existential threat" for vulnerable populations without access to air conditioning or other ways to keep cool.
The new report –– which calculated the average of daily maximum temperatures in March and April across a large swathe of northwestern India and southern Pakistan –– may underestimate the frequency of such heatwaves, today and in the future, the authors noted.
Indeed, an assessment by Britain's Met Office using somewhat different methods concludes that heating to date increased the likelihood of the India and Pakistan scorcher 100-fold.