Extreme heatwave in India mostly exacerbated by human-driven climate change: Report

Human-driven climate change and natural climate variability both played a role in increasing the heat during the May 2024 heatwave, says the report

A new report looked into the severe heatwave that gripped major parts of central and northern India between May 26 to May 29. The report by ClimaMeter found that heatwaves similar to the May 2024 India heatwave are almost 1.5°C warmer than the warmest heatwaves previously observed in the country, even though they occur much later than the southern hemisphere summer seasons.

More than 37 cities in the country recorded temperatures over 45°C. The heatwave in India and Southern Pakistan exhibited record-high temperatures, ranging from 45.2°C to 49.1°C in different parts of New Delhi.

The report analysed how events similar to the high temperature in India during the May heatwave changed in the present (2001–2023) compared to what they would have looked like if they had occurred in the past (1979–2001) in the region.

According to the report, the temperature changes showed that similar events produced at least 1.5 °C warmer temperatures in the present climate than what they would have been in the past, over a large area of the region analysed. Temperature data indicated warm anomalies reaching up to +5°C in some parts of northwest India and southern parts of Pakistan.

Changes in urban areas revealed that New Delhi, Jalandhar and Larkana (Pakistan) are more than 1°C warmer in the present compared to the past, results that are in agreement with the adjusted readings from the India Meteorological Department (IMD), after removing the wrong reading of 53.2°C.

While the precipitation changes did not show any significant variations, windspeed changes indicated up to 4 km/h windier conditions over southern western regions. The study also noted that similar events previously mainly occurred in November and December, while in the present climate they are mostly occurring in February and May.

Finally, the report found that sources of natural climate variability, notably the Pacific Decadal Oscillation may have influenced the event. This means that the changes in the event compared to the past may be mostly due to human driven climate change.

The report interpreted the heatwave as a largely unique event whose characteristics can mostly be ascribed to human driven climate change.

Existing climate science confirmed

The Intergovernmental Panel on Climate Change (IPCC) Assessment Report 6 (AR6) report provided a clear relationship between heatwaves and climate change in India. In most land regions, there has been a high degree of confidence in the increased frequency, intensity, and duration of heat-related events, including heatwaves, as a result of climate change-related warming. The report stated that climate change is significantly contributing to the rise in heatwaves in India through various mechanisms.

IPCC reports have showed how climate change is projected to alter land conditions, affecting temperature and rainfall in regions. This could result in increased winter warming due to decreased snow cover in boreal regions and reduced warming during the growing season in tropical areas, accompanied with increased rainfall. Rising urbanisation and global warming can lead to warmer cities and surroundings, especially during heatwaves, with a higher impact on night-time temperatures than daytime temperatures.

The IPCC reports further add that observed surface air temperature has been increasing since the 20th century in Asia, intensifying the threat of heatwaves across the region. In India specifically, the frequency and duration of heatwaves have increased, associated with Indian Ocean basin-wide warming and frequent El Ninos. This has resulted in severe impacts on agriculture and human discomfort. The combination of global warming and population growth in already-warm cities in regions like India is a major driver for increased heat exposure, with urban heat islands elevating temperatures within cities relative to their surroundings.

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