The clouds that bring life-sustaining rain to our fields are changing.
As India welcomes another monsoon season, climate experts are turning their attention skyward — and with good reason. The clouds that bring life-sustaining rain to our fields are changing in ways that could have long-term implications for agriculture, weather forecasting, and climate resilience.
A recent study led by Saloni Sharma, along with researchers Piyush Kumar Ojha, Vaibhav Bangar, Chandan Sarangi, Ilan Koren, Krishan Kumar, and myself, from the School of Environmental Sciences, Jawaharlal Nehru University, in collaboration with IIT Madras and Weizmann Institute of Sciences, Israel, offers compelling observational evidence of how global warming is reshaping India’s monsoonal cloud patterns.
The research, published in Science of the Total Environment (Elsevier, July 2024), focuses on how the vertical structure and type of clouds over the Indian subcontinent have evolved during the first two decades of 21st century.
For a country like India, where nearly half the population depends on agriculture, even subtle changes in monsoon behaviour can have enormous consequences. Shifts in cloud height and types affect how, when and where rain falls — affecting everything from crop yields to groundwater recharge.
Using 20 years of radiosonde data from 16 locations across India, the researchers found that the number of cloudy days during the monsoon season has increased by around 13 per cent per decade. However, this doesn’t mean more low level, rain-heavy clouds. In fact, low-level clouds have decreased by 8 per cent, while high-level clouds — which often trap heat — have increased by about 11 per cent per decade.
This shift in cloud types is significant. Low-level clouds are typically thicker and more effective at reflecting sunlight, helping to cool the Earth’s surface. High-level clouds, by contrast, tend to trap heat. The study found that not only are these higher clouds becoming more common, but they are also forming at greater altitudes as the atmosphere warms and expands.
Also, lower clouds, which are declining, are typically associated with more consistent rainfall. High clouds, which are increasing, may not precipitate at all or could be associated with extreme weather events.
Global warming
These changes in cloud structure are largely driven by global warming, which is altering the thermodynamic state of the troposphere. The study observed the greatest temperature increases in the upper layers of the atmosphere, with the equivalent potential temperature — a key indicator of atmospheric stability — rising more sharply in higher altitudes. This indicates more moisture and heat being transported upward, leading to the formation of high clouds.
The researchers also recorded a rise in tropopause height (the upper boundary of the troposphere) by 480 meters per decade, reinforcing the idea that the atmospheric column is stretching vertically due to global warming.
To further understand the drivers of these changes, the researchers examined large-scale climate indicators such as the Global Warming Index (GWI), North Atlantic Oscillation (NAO), and ENSO (El Niño-Southern Oscillation). They found strong statistical correlations between GWI (rising temperatures) and the increase in high-level cloud frequency over India.
Their analysis revealed that cloud formation patterns are not merely a local phenomenon, but are influenced by broader, global climate systems. This reinforces the need for India to invest in climate-resilient agriculture and better forecasting models.
This research offers the clearest observational evidence yet that India’s monsoon clouds are being reshaped by climate change. It calls for urgent attention to how these changes will affect our food security, water availability, and disaster preparedness in the coming years.
As the 2025 monsoon sets in, it is a timely reminder that climate change isn’t a far-off threat— it’s already in the air around us.
(The writer is Assistant Professor, School of Environmental Sciences, Jawaharlal Nehru University, New Delhi)
