Efforts to improve air quality in India could inadvertently accelerate warming and intensify extreme heat if not accompanied by reductions in greenhouse gas emissions, researchers have warned.
A study published in Geophysical Research Letters in November 2024 found that regions that successfully cleaned their air in the late 20th century experienced greater increases in warming over time. The analysis also indicated that heavily polluted urban areas with lower human development indices had seen reduced warming due to the cooling effect of aerosols.
“Abruptly halting aerosol emissions can increase the rate of warming in the short term,” said Aditya Sengupta, a graduate researcher at the University of Melbourne and the study’s lead author.
Balancing Air Quality and Climate Impact
While greenhouse gases such as carbon dioxide and methane trap heat and contribute to global warming, aerosols—tiny particles from sources such as industrial emissions and vehicle exhaust—scatter solar radiation and create a cooling effect. Sulphate aerosols, a major component of India’s pollution mix, are highly reflective and significantly influence regional temperatures.
Govindasamy Bala, a professor at the Centre for Atmospheric and Oceanic Sciences at the Indian Institute of Science in Bengaluru, noted that India’s reliance on coal-based thermal power plants, which generate around 70% of its electricity, contributes heavily to sulphur dioxide emissions.
“If these emissions are reduced without a simultaneous decrease in greenhouse gases, the cooling offset from aerosols will disappear, and warming could intensify,” Bala said.
India’s Climate Trade-offs
Research has found that between 1906 and 2005, India’s warming was measured at approximately 0.54 degrees Celsius. However, greenhouse gases alone would have driven a 2-degree increase, with aerosols offsetting about 1.5 degrees of warming, said Krishna AchutaRao, a professor at the Centre for Atmospheric Sciences at IIT Delhi.
Aerosols also impact the Indian monsoon. Bala pointed to findings from the Intergovernmental Panel on Climate Change (IPCC), which showed that aerosols have contributed to reduced rainfall over India by disproportionately cooling the northern hemisphere.
However, removing aerosols could increase rainfall, although researchers warn that regional variations in the effects of aerosols make precise predictions difficult. A 2024 study in Proceedings of the National Academy of Sciences found that China’s aerosol reductions worsened extreme heatwaves along the Pacific coast of North America, indicating that changes in one region can have global consequences.
Need for Policy Adaptation
Experts emphasize that India must prepare for the consequences of reducing air pollution. While cleaner air will have immediate health benefits, vulnerable populations—especially in the Indo-Gangetic plains, where aerosol pollution is highest—could face greater heat stress.
“Achieving net-zero emissions will not be the end of the story,” Sengupta said. “Policymakers must implement long-term adaptation strategies to support at-risk communities.”
A recent report by the Delhi-based Sustainable Futures Collaborative found that heat action plans in major Indian cities such as Mumbai, Delhi, and Bengaluru lack comprehensive long-term strategies. If aerosol emissions are cut, these cities could experience even more severe heat stress.
Despite these challenges, experts agree that reducing air pollution is crucial. “While cleaning the air might accelerate warming by unmasking greenhouse gas-induced heating, the health benefits outweigh the risks,” Bala said.
