ClimaMeter analysis of India-Pakistan heatwave in April this year.
| Photo Credit:
www.climameter.org, david.faranda@cea.fr
Natural climate variability, notably El Nino, may have influenced severe heat wave that struck India and Pakistan in mid-April, according to ClimaMeter, a rapid experimental framework for putting weather extremes in a climate perspective.
Consequences extended beyond human health impacting essential services, education, and food production, with experts warning of growing vulnerability of both countries to such climate extremes in future, ClimaMeter analysis said.
Passive El Niño role
It added a caveat saying since current phase in equatorial Pacific is ‘neutral’ (neither El Niño nor La Niña), observed changes in heatwave are likely due to human-driven climate change, with only a minor contribution from natural variability.
ClimaMeter evolved at Laboratoire des Sciences du Climat et de l’Environnement (Institut Pierre Simon Laplace in Paris-Saclay. It said meteorological conditions similar to April event had turned up to 4°C warmer this year than in past. It interpreted this as driven by ‘very exceptional conditions whose characteristics can mostly be ascribed to human-driven climate change.’
Mid-April heat wave
During April 14 to 15, parts of Pakistan, particularly Balochistan, saw temperatures soar to up to 49°C. Early arrival of heatwave caught many off guard, with local residents experiencing power outages lasting up to 16 hours. In India, New Delhi reported temperatures surpassing 40°C on multiple occasions, up to 5°C above seasonal average. The heatwave spread across neighbouring states such as Rajasthan, where labourers and farmers struggled to work in the scorching conditions.
Meteorological patterns
Early heat and water shortages ensured agricultural sector was hit hard. Extreme temperatures also led to increased demand for electricity, worsening power shortages. Ensuing reliance on groundwater is negatively impacting aquifers of region. Past events suggest meteorological patterns associated with heatwave occur with same frequency as they did in the past. Changes in urban areas reveal that New Delhi, Jaipur, and Islamabad are experiencing warmer conditions, with Islamabad being most affected.
Pressure anomalies
Meteorological conditions were characterised by unusual pattern of surface pressure anomalies, with scattered negative (lower) pressure anomalies over Pakistan and positive (higher) pressure anomalies over Himalayas. Lower pressure meant rising air, moisture, clouds and rain, while higher pressure brought in descending air and dryness that did not allow clouds to form.
Temperature anomaliesreached up to +12°C across Afghanistan, Pakistan, and India. Precipitation data indicate dry conditions in the area affected by heat under calm (wind-less) conditions, which merely exacerbated heating and discomfort.
Becoming commonplace
Occurrence of large positive anomalies of temperature and extremely dry conditions in pre-monsoon season (March to May) is becoming commonplace in South Asia, as shown by persistent and spatially extended events in 2015, 2019, 2022 and 2024, with temperature records being shattered every few years, ClimaMeter analysis showed..
The IPCC AR6 report provides a clear relationship between heatwaves and climate change in South Asia. Climate change is significantly contributing to increase in heatwaves in India through various mechanisms: warming has led to increased frequency, intensity, and duration of heat-related events, including heatwaves in most land regions (IPCC SR OC C6 – Page 27).
Temperature spikes
Global warming and urbanisation can enhance warming in cities and their surroundings, especially during heatwaves, with a higher impact on night temperatures than day temperatures (IPCC AR6 WGII FR – Page 1058). Observed surface air temperature has been increasing since the 20th century in Asia, intensifying threat of heatwaves across the region.
In South Asia specifically, frequency and duration of heatwaves have increased, associated with Indian Ocean basin-wide warming and frequent El Ninos. Combination of global warming and population growth in already-warm cities India is a major driver for increased heat exposure, with urban heat islands elevating temperatures in cities relative to their surroundings.
Published on April 22, 2025