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India has continued to warm over the past two decades, but its surface temperatures have risen considerably more slowly than those across other northern tropical land areas. New research suggests that aerosols and increased cloud cover have blocked enough sunlight to temporarily mask a substantial portion of the warming.
Between 2001 and 2024, India’s average warming rate was about 0.138 degrees Celsius per decade, compared with roughly 0.280 degrees Celsius per decade across northern tropical land. The findings indicate that atmospheric particles and clouds reduced the amount of solar energy reaching India’s surface.
The study was led by Vijayakumar S. Nair of the Vikram Sarabhai Space Centre and combined satellite measurements with observations from monitoring stations across India. Researchers examined changes in aerosols, clouds, incoming sunlight and temperature from 2001 through 2024.
Aerosols are tiny particles suspended in the atmosphere. They can come from natural sources such as dust, as well as human activities including fuel combustion and industrial emissions. Depending on their composition, they can scatter or absorb sunlight and alter the amount of energy reaching the ground.
The researchers found that aerosol levels increased in parts of India, particularly central regions and the east coast. However, the composition of those particles also changed. Black carbon and dust declined at several monitoring sites, leaving a mixture that was more effective at scattering sunlight and less effective at absorbing it.
Clouds had an even larger cooling influence. Cloud cover increased particularly across central and western India, with low-level clouds playing an important role because they prevent sunlight from reaching the surface.
The study estimated that changes in aerosols reduced India’s warming trend by about 0.042 degrees Celsius per decade, while changes in clouds reduced it by approximately 0.083 degrees. Combined, the two effects amounted to about 0.125 degrees Celsius of cooling per decade, nearly matching the observed warming rate of 0.138 degrees.
Without this surface dimming, the researchers estimate India’s warming rate could have been close to 0.268 degrees Celsius per decade.
The findings do not mean pollution is protecting India from climate change. Aerosols are associated with serious health and air-quality problems, and their cooling influence can change as emissions decline.
Scientists also caution that the causes of increased cloud cover remain uncertain. Changes in atmospheric moisture, weather patterns, natural climate variability and greenhouse warming could all contribute.
The researchers say reducing uncertainty around aerosol-cloud interactions will be important for future climate projections, particularly as India improves air quality and atmospheric pollution declines.
