Explained | How Is Climate Change Impacting India's Heatwaves

India has been battling probably the worst heatwave in its history, making global headlines.

India has been battling probably the worst heatwave in its history, with scorching day temperatures baking almost 15 states of the country during the first week of May. Series of heat waves in India and neighbouring Pakistan have made headlines globally for unprecedented temperatures.

March has been recorded as the hottest in 122 years from 1901-2022. April was not far behind, with Northwest and Central India being the hottest in the same time period. Overall, it was the fourth hottest April the country has witnessed. March recorded three days of heatwave against the normal of one day.

Meanwhile, April registered 10 days of heatwave against the average of three days. It is not only the intensity of the heatwave but also its prolonged duration this season, which has tested the limits of human survivability and our preparedness.

Several places recorded maximum day time temperatures in the range of 44-46°C for several consecutive days, while a few places even touched the 47°C mark.

Experts have already established the fact that both March and April are warming much faster than core summer months of May and June. The long persistence of heatwave has highlighted global warming’s cascading effect on the temperature profile across the country. Both the frequency and intensity have increased sharply over the last few decades.

Climate change is not only raising temperatures and making India’s heatwaves hotter, but is also changing weather patterns that further drive dangerous heat extremes.

What are Western Disturbances And How Does Climate Change Impact Them?

These can be defined as storms that originate in the Caspian or Mediterranean Sea, bringing non-monsoonal rainfall to Northwest India and adjoining areas of Central India.

In simpler words, WDs drive the weather and govern the wind pattern over the region that includes both mountains and plains. In fact, they are very crucial in the summer season as they are known to suppress heat wave conditions in the Indo-Gangetic plains.

However, climate change has led to dynamic changes in the pattern of WDs. Although the frequency of Western Disturbances has increased, those have not translated to the precipitation associated with them.

“Global warming can be held responsible up to an extent. WDs are getting lighter by virtue of increasing heat, as it decreases the moisture content."

A P Dimri, Director, Indian Institute of Geomagnetism, Mumbai.

In the last two months, the country witnessed only four WDs travelling through Western Himalayas between March and April. They were feeble in nature and thus, restricted their effect to mountains only.

What are Anti-Cyclones?

This weather phenomenon can be defined as large-scale circulation of winds around a central region of high atmospheric pressure. While a cyclone attracts the winds around it, anticyclone throws the winds in all directions as it rotates clockwise.

Formation of anticyclones was nothing abnormal as they usually develop over Northwest India during summers. However, it is the longer persistence of these anticyclones that exaggerated the heatwave conditions in India.

This is another indirect impact of changing climatic conditions.

This season, we saw anticyclones with their centre hovering around Rajasthan and adjoining Pakistan.

Arctic Heatwave Impact on in India

Arctic heat waves have been breaking records this season, with the annually averaged Arctic near-surface air temperature increasing by 3.1°C from 1971–2019, which is three times faster than the global average.

There has been an increase in extreme high temperatures and a decline in extreme cold events. Cold spells lasting more than 15 days have almost completely disappeared from the Arctic since 2000.

“Above normal temperatures across the Arctic region are a major cause of concern as it directly impacts the circulations affecting the Asia region."

Mahesh Palawat, VP- Meteorology and Climate Change, Skymet Weather.

According to scientists and meteorologists, if the Arctic heatwave continues, we might see a greater number of hotter days quite early in the season, with their potential impact on WDs.

According to a report, “Arctic Climate Change Update 2021: Key Trends and Impacts’, Arctic snow cover extent during the months of May through June declined by 21% from 1971 to 2019, with a larger decrease (25%) over Eurasia compared with North America (17%).

La Niña and its Impact on Heatwave

Last but not the least, the relation between ENSO (El Nino Southern Oscillation) and the heatwave cannot be ignored.

The IPCC Report had already warned that in the warming atmospheric conditions, the associated ENSO precipitation variability on regional scales is likely to intensify.

The La Niña pressure pattern has been splitting the hot air over the Arabian Sea south into western India and north into Pakistan and northern India.

The La Niña is usually associated with intense winters and wet Monsoon in India. While La Niña was earlier predicted to crash by the spring of 2022, but it is far away from this.

Sea Surface temperatures continue to be well below normal in the Tropical Pacific. This has aided La Nina to survive through the spring season and rather extend far into 2022 till Monsoon arrival.

The ongoing episode of La Nina had begun with Monsoon 2020 and is still holding the fort. According to latest predictions, a mild drop in the temperatures is expected during July-August 2022.

According to meteorologists, La Nina has defied its crash as cold-water layers seem to be more stable than before, therefore delaying the expected warming of the ocean.

“The north-south pressure pattern has been persisting over India, with La Nina extending its stay over the Pacific. This has definitely impacted the weather over India, which has been seen even during 1998-2000 when La Nina had persisted for three years."

Raghu Murtugudde, Professor, department of atmospheric and oceanic science, University of Maryland.

More Frequent, Harsher, Prolonged Heatwaves Await India

According to the Ministry of Earth Sciences report, ‘Assessment of Climate Change over the Indian Region’, all India averaged frequency of summer heatwaves will increase to about 2.5 events per season by the mid-21st century under the medium emission scenario.

The average total duration of summer heatwaves is projected to increase to about 15 and 18 days per season during the mid- and end-twenty-first century respectively under this future scenario.

Worse is in store for southern India, which is currently not influenced by heatwaves, and is expected to be severely affected by the end of the twenty-first century.

With all these parameters interlinked, as the recently released IPCC WG2 Report ‘Climate Change 2022: Impacts, Adaptation and Vulnerability’ warned, we are moving to tougher times ahead as heat waves will continue to become more frequent, harsher and prolonged.

In near future more frequent and long-lasting heatwave events are projected to affect the Indian sub-continent in response to the warming of the tropical Indian Ocean and the increasing frequency of extreme El Nino events.

(This story contains inputs shared by Climate Trends, India, a climate communications initiative.)