Climate crisis link to March-April heatwave

The March-April spring heatwave spell in India and Pakistan was about 30 times more likely to happen because of human-caused climate change, a rapid attribution analysis by an international team of leading climate scientists who are part of the World Weather Attribution network said on Monday.
 (AFP) PREMIUM
(AFP)
Updated on May 24, 2022 03:17 PM IST
Copy Link
ByJayashree Nandi, New Delhi

The March-April spring heatwave spell in India and Pakistan was about 30 times more likely to happen because of human-caused climate change, a rapid attribution analysis by an international team of leading climate scientists who are part of the World Weather Attribution network said on Monday.

The results of the rapid analysis showed that an unusually long and early onset heatwave spell like the one India and Pakistan just experienced is very rare, with a chance of occurring only once in 100 years. “But human-caused climate change has made it about 30 times more likely to happen, meaning it would have been extraordinarily rare without the effects of human-induced climate change,” the scientists said in a statement.

Large parts of India and Pakistan experienced an unusually early and long heatwave, beginning in early March, which persisted until last week. A western disturbance brought relief from extreme heat over the weekend causing thunderstorms and dust storms across northwest India.

This year’s spring heatwave is estimated to have led to at least 90 deaths across India and Pakistan, triggered an extreme Glacial Lake Outburst Flood (GLOF) in northern Pakistan and forest fires in India, particularly in the hill states of Uttarakhand and Himachal Pradesh; extreme heat also reduced India’s wheat crop yields, causing the government to stop wheat exports; shortage of coal led to power outages that limited access to cooling by affected people, the analysis said. HT also reported that the heatwave spell may have caused serious health impacts and mortality which may not have been documented.

To quantify the effect of climate change on the high spring temperatures in India and Pakistan, scientists analysed weather data and computer simulations to compare the climate as it is today (with 1.2°C of global warming compared to pre-industrial levels) with that in the pre-industrial period. The team estimated that the return period of such an unusual heat wave spell to be around 100 years in today’s climate of 1.2°C global warming. “We thus use 1 in 100 years as the event definition for the attribution study,” the analysis said. The same event would have been about 1°C cooler in a pre-industrial climate, the team added.

The analysis focused on the average maximum daily temperatures during March and April, in northwestern India and southeastern Pakistan.

“The results showed that an event like the current long-running heatwave is still rare, with a 1% chance of happening each year, but human-caused climate change has made it about 30 times more likely to happen, meaning it would have been extraordinarily rare without the effects of human-induced climate change,” scientists concluded.

Until overall greenhouse gas (GHG) emissions are halted, global temperatures will continue to rise and intense heat wave events will become more frequent. For example, if global temperature rise reaches 2°C, a heatwave like this would be expected as often as once every five years, the scientists found. “That basically means in a worst-case scenario, a once in a 100-year event can return once in 5 years,” explained Prof Arpita Mondol from the Civil Engineering, and Climate Studies department of IIT Bombay who was part of the analysis, during a press briefing on Monday.

March was the hottest in India in 122 years with Pakistan also seeing record temperatures. March was also extremely dry, with 62% less rain than normal over Pakistan and 71% below normal over India. At least 90 people have died as a result of the heatwave, a toll that will almost certainly increase substantially with more reporting, scientists said. Around 300 large forest fires occurred in India on April 28 alone, a third of those happened in Uttarakhand. By April 29, almost 70% of India was affected by the heatwave. In Pakistan, temperatures above 49°C were recorded in Jacobabad in Sindh, and 30% of the country was affected by the heatwave. Towards the end of April and in May, the heatwave extended into the coastal areas and eastern parts of India.

Adaptation to extreme heat can be effective at reducing mortality however, authors said pointing to India’s example of issuing early heat warnings.

“Heat Action Plans that include early warning and early action, awareness raising and behaviour changing messaging, and supportive public services can reduce mortality, and India’s rollout of these has been remarkable, now covering 130 cities and towns,” the analysis said. Authors of the analysis said that the Ahmedabad Heat Action Plan which has been implemented since 2013 have managed to reduce heat wave related mortality over the years and IMD’s impact-based warnings are also helping people prepare for heat wave spells.

The analysis was conducted by 29 researchers as part of the World Weather Attribution group, including scientists from universities and meteorological agencies in India, Pakistan, Denmark, France, the Netherlands, New Zealand, Switzerland, the UK and the US.

“High temperatures are common in India and Pakistan but what made this unusual was that it started so early and lasted so long. Across much of both countries, people had little relief for weeks on end, with the costs particularly high for hundreds of millions of outdoor workers. We know this will happen more often as temperatures rise and we need to be better prepared for it,” Prof Krishna AchutaRao, Centre for Atmospheric Sciences, IIT Delhi said in a statement.

“We are giving weather and climate data for the 130 cities and towns which are being monitored by us. The National Disaster Management Authority is preparing the heat action plans but the guidelines for implementation of these plans are being prepared by concerned state governments. We are taking all measures to be better prepared for heat extremes. I do not wish to comment on the other findings of this analysis,” said M Mohapatra, director general, IMD responding to the analysis.

On Saturday, IMD and IIT Delhi scientists wrote in Nature journal that the summer of 2022 unfolded in an unusual way as early as 11 March mostly over the plains of northwest, central India, Gujarat and the western Himalayan region. The ‘major’ and ‘severe’ heat waves came in six spells: March 11-23, March 27- April 12, April 17-20, April 23- May 2, May 7-16 and May 19-21. Most of these spells were over the plains of northwest and central India, Gujarat and parts of western Himalayan region, southern parts of Uttar Pradesh, Jharkhand and the national capital region of Delhi. The period of April 24-30 is the only one when it spread further east to some parts of West Bengal and Odisha.

A comparison of heat waves of the past 13 years (2010-2022) shows record highs this year. March had the highest number (93) of meteorological subdivision days (MSD). MSD is the sum of the heatwave days in different meteorological subdivisions of the country. April 2010 had the highest number (404) of MSDs of heat waves followed by 2022 at 209 MSDs.

Enjoy unlimited digital access with HT Premium

Subscribe Now to continue reading
freemium
SHARE THIS ARTICLE ON
Close Story
SHARE
Story Saved
×
Saved Articles
Following
My Reads
Sign out
New Delhi 0C
Wednesday, June 29, 2022