Warming atmosphere supercharges Indian monsoons

In the summer of 2018, extreme rainfall caused catastrophic flooding and triggered landslides in Kerala, India. In the end, the disaster took the lives of more than 400 and the homes of more than a million. Although India typically experiences the majority of its rainfall during monsoon season, this flooding was the worst Kerala had seen since 1924.

Many factors likely contributed to the devastation, including warming as a result of climate change, and events like these are on the rise.  

On 12 February 2025, the research paper, “Observational Evidence of Increasing Intensity and Frequency of Deep Convective Clouds During the Indian Summer Monsoon Season” was published in the American Geophysical Union’s Geophysical Research Letters. Dr Viju John from EUMETSAT, Dr Roshny Antony, Dr Ajil Kottavil, and Dr K. Satheeshan from the Cochin University of Science and Technology, and Dr Prince Xavier from the UK Met Office   analysed satellite climate data for the period 2000-2020 to identify changes to the Indian summer monsoons.

They found that deep convective cloud tops above India and the surrounding waters increased substantially over the period 2000 to 2020 and that this type of cloud appeared much more frequently near the end of the period than at the beginning.

“On colder mornings, you see dew on the grass,” said John, a climate product expert. “But you do not see that on warmer days because warmer air can hold more moisture without that water condensing.

“The same thing happens in the atmosphere. When the atmosphere is warmer, it can hold more water without condensing. So, when the air is warm and conditions favour producing convective clouds, those clouds can hold much more water, which means more rain is poured down onto the ground.”

For their investigation, the researchers relied heavily on data from EUMETSAT-operated satellites. They analysed both gridded satellite data, which includes observations from Meteosat satellites located over the Indian Ocean since 1998, and data from the fifth generation European Centre for Medium-Range Weather Forecasts reanalysis, which includes a substantial portion of data from EUMETSAT and the Satellite Application Facilities.

They discovered a significant increase in the altitude of deep convective clouds – high storm clouds – in the regions across India they studied. By using observations from satellite instruments that measure the temperature of cloud tops, they inferred that the colder cloud tops were higher, since the atmosphere decreases in temperature with increased altitude.

They also discovered that there were more convective clouds, which aligns with the increased frequency of extreme rainfall events during the summer monsoon season. Rather than the diffuse rain typical for Indian summer monsoons, the rains have become more intense.

The authors also noticed that these changes did not happen uniformly.

“Something happened around 2010 or 2015 – after that there were many more of these extreme events,” said John. “Maybe there was a paradigm shift in the nature of the formation of these clouds.”

This may point to an alarming trend.

“With a one degree increase in air temperature, the air can hold 7% more water,” said John.

“Then if the air temperature increases further, the amount of water the air can hold actually increases exponentially. So, as the Earth and its atmosphere warms, the amount of water in the atmosphere and the likelihood of all the dangers caused by these extreme events related to that is actually also increasing.”

These findings underscore the importance of maintaining satellites that deliver high quality observations. These observations, in turn, inform climate records that make studies like this possible.

“In recent years, there have been many devastating consequences of extreme rainfall such as flash flooding and villages being washed away, not just in Kerala but also at the foothills of Himalayas,” said John. “But this is not limited to India. "We all saw the consequences of the severe flooding in Valencia in 2024 and the similar situation in the Ahr Valley in Germany in 2021.

“These events happen for similar reasons everywhere, with a similar physical mechanism behind them – increasing temperatures increase the capacity of the atmosphere to hold more moisture. And unfortunately, this kind of event will continue to become more frequent and intense if the world does not do anything to tackle rising global temperatures.”

Author: 

Sarah Puschmann