‘There is reason to believe controlling air pollution can increase temperatures’

India faces a double-edged environmental crisis: Efforts to reduce aerosol air pollution — tiny particles in the air from industrial emissions, burning fossil fuels and biomass — may accelerate atmospheric warming, leading to more frequent and intense heatwaves. This raises the risk of hotter summers and more frequent and intense heatwaves in the coming decades.

The country has warmed about half as much as other regions in the northern hemisphere, using 1951-1980 as the baseline, according to data from the United States’ National Aeronautics and Space Administration (NASA). While the precise reasons for this anomaly remain underexplored, contributing factors could include high aerosol loads and extensive irrigation, both of which suppress local temperature increases.

Down To Earth spoke with David Shumway Jones, Professor of the Culture of Medicine at Harvard University and an expert on the history of air pollution in India, to explore why India’s warming rate has slowed and how reduced aerosol pollution could affect future warming and heatwaves.

Akshit Sangomla (AS): What is the current health burden of India’s aerosol air pollution crisis?

David Shumway Jones (DSJ): The most recent estimate I’ve seen, from researchers at the Harvard School of Public Health, is that India experiences around 1.5 million excess deaths each year due to air pollution. That mortality figure is likely just the tip of the iceberg, but it would be very hard to gauge the impact of air pollution on general levels of health and well-being. It’s reasonable to assume that many people suffer from respiratory issues or have cardiac or other disease symptoms partially linked to air pollution.

AS: How and when, according to current and future policies, do you think it can be controlled?

DSJ: Air pollution can certainly be brought under control. Countries such as the United Kingdom, United States, Mexico and China have shown that concerted efforts can lead to a marked reduction in pollution. So yes, it could be controlled in India. 

But is it likely? That’s harder to say. Air pollution is caused by a variety of sources; each city has its own distinct mix of sources, necessitating a unique set of policies. I spoke to some local experts in Delhi who seemed quite pessimistic. They feel that air pollution is receiving far less attention now than it did five years ago. There’s a sense that people in Indian cities are becoming resigned to shortened lifespans.

AS: If aerosol pollution is reduced, surface warming may accelerate. This could worsen health risks from extreme heat. How can India navigate this paradox?

DSJ: There is reason to believe that control of air pollution can increase temperatures. This is based on research that suggests that lowering the sulphur content of diesel fuels used in maritime shipping has contributed to the recent hot years. This is based on intuition: Cloud layers reflect sunlight, so if there is a layer of air pollution, it will also reflect sunlight back into space. So, controlling pollution might make India hotter.

But that remains a possibility, not a certainty. Many countries — such as the US, UK and China — have curbed air pollution. Have they become hotter as a result? The US is hotter now than it was in the more polluted early 20th century; is this due to air pollution control, rising carbon dioxide levels, or something else?I assume that could be sorted out, but I don’t know if anyone has tried. 

Similarly, has air pollution control in eastern China resulted in hotter temperatures? I discovered an article reporting such a link in China while researching this.I have not seen any similar claims that air pollution control in the US has contributed to warming.

Given that far more people at present die from air pollution than from heat, even if air pollution control increased warming, I believe the net health benefit would be positive.

AS: Do you think the Indian government is doing enough to counter the crisis?

DSJ: I assume people will disagree on whether the government is doing enough. It depends on whether you are looking at the city, state, or national government and the answer will most likely differ by city. Some cities, like Ahmedabad, seem to have robust plans for both heat and air pollution. One speaker at a conference reported that heat mortality rates in Ahmedabad have declined over the past decade, following implementation of its heat action plan.

Delhi has surely benefitted from phasing out diesel buses, a campaign led by the Delhi-based think tank Centre for Science and Environment in the 1990s. But on the whole, the picture is more pessimistic. Other perspectives are more pessimistic. 

For example, air pollution in China first received international attention in 2008 (during the Summer Olympics). Since then, government action has resulted in dramatic improvements in air quality, particularly in major eastern cities like Beijing, Shanghai and Guangzhou.

Meanwhile, air pollution in India gained international attention in 2010 during the Commonwealth Games in Delhi or 2016 at the start of annual international media attention for Diwali air pollution crises. But, as far as I can tell, air pollution in India is now worse than it was 10-15 years ago; levels reported in November-December 2024 were remarkably high. This suggests that the Indian government isn’t doing enough. 

I think there has been progress, such as more CNG autorickshaws on Delhi’s streets in 2025 than when I first visited in 2013, but not enough progress. Electric vehicles, for example, appear to be pretty rare in Delhi, in stark contrast to cities in China, Europe and the US.