A full health and economic fallout, and cascading effects from the current heat wave will take months to determine, including excess deaths, hospitalisations, lost wages, missed school days, and labour productivity.
Since the beginning of March, India, Pakistan and large parts of South Asia experienced prolonged heat. But, scientists warn of a repeat of the worst March-April summer ever experienced. They say that the same event would have been about 1C cooler in a pre-industrial climate.
The scientists are part of the World Weather Attribution group that has analysed historical weather data from India and Pakistan. According to their analysis, March was the hottest in India since records were first documented 122 years ago. Pakistan recorded the highest worldwide positive temperature anomaly during March. Many individual weather stations recorded monthly all-time highs through March.
The group suggested that early, long heat waves over the huge SouthAsian landmass are rare, once-a-century events.
“March was extremely dry, with 62 per cent less than normal rainfall reported over Pakistan and 71 per cent below normal over India, making the conditions favourable for local heating from the land surface,” the group said in its report published Monday.
“The heatwave continued over the month of April and reached its preliminary peak towards the end of the month. 70 per cent of India was affected by the heatwave by 29 April.”
Scientists from India, Pakistan, the Netherlands, France, Switzerland, New Zealand, Denmark, United States of America and the United Kingdom, collaborated to assess to what extent human-induced climate change altered the likelihood and intensity of the heatwave.
While heatwaves are not uncommon in the season preceding the monsoon, the very high temperatures so early in the year coupled with much less than average rain have led to extreme heat conditions with devastating consequences for public health and agriculture, their report says.
A complete health and economic fallout, and cascading effects from the current heat wave will however take months to determine, including the number of excess deaths, hospitalisations, lost wages, missed school days, and diminished working hours. Early reports indicate 90 deaths in India and Pakistan, and an estimated 10-35 percent reduced crop yields in Haryana, Uttar Pradesh, and Punjab due to the heatwave.
The early and prolonged heat particularly affected India’s North West South Pakistan, the so-called bread basket of the subcontinent. Towards the end of April and in May the heatwave also reached more coastal areas and the Eastern parts of India. It was however the early, prolonged and dry heat that made this event stand out as distinct from heatwaves occurring earlier this century.
Using published peer-reviewed methods, the group analysed how human-induced climate change affected the heat in the early affected region that also experienced a lot less rain than usual. To capture the duration of the event we chose the March-April average of daily maximum temperatures.
With future global warming, heatwaves like this will become even more common and hotter, their report says. “At the global mean temperature scenario of +2C such a heatwave would become an additional factor of 2-20 more likely and 0.5-1.5C hotter compared to 2022.”
“We note here that our results are likely conservative; the relatively short lengths of observed data rendered it difficult to consider statistical fits that are more ideal for extremes. In large model ensembles more accurate fits indicate a larger increase in likelihood.”
It is important to note that this early heatwave was accompanied by much below average rainfall and humidity and thus constituted a dry heatwave, rendering humidity much less important for health impacts than heatwaves occurring late in the season and in coastal areas.
30-times more likely
The 2022 heatwave triggered an extreme Glacial Lake Outburst Flood in northern Pakistan and forest fires in India. The report also refers to the shortage of coal in India that led to power outages that, in turn, limited access to cooling, compounding health impacts and forcing millions of people to use coping mechanisms such as limiting activity to the early morning and evening.
The SouthAsian heatwave also left behind a geopolitical and global trade impact as it led to a reduction of India’s wheat crop yields and led the government to reverse an earlier plan to supplement the global wheat supply impacted by the war in Ukraine.
The group’s report says, “we estimate the return period to be around 100 years in today’s climate of 1.2C global warming. We thus use 1 in 100 years, as the event definition for the attribution study.”
“Because of climate change, the probability of an event such as that in 2022 has increased by a factor of about 30,” the report warns.
In Pakistan and India, extreme heat hits hardest for people who must go outside to earn a daily wage (e.g. street vendors, construction and farm workers, traffic police), and consequently lack access to consistent electricity and cooling at home, limiting their options to cope with prolonged heat stress.
Rising temperatures from more intense and frequent heat waves will render coping mechanisms inadequate as conditions in some regions meet and exceed limits to human survivability. Mitigating further warming is essential to avoid loss of life and livelihood.
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