How air pollution is stealing India’s sunshine

India is losing sunlight.

A a new study by six Indian scientists found that over the past three decades, sunshine hours — the time it takes for direct sunlight to reach the Earth’s surface — have steadily declined over much of India, driven by clouds, aerosols and local weather.

Data from 20 weather stations from 1988 to 2018 show a steady decline in sunshine hours across the country, with only the Northeast region experiencing a slight seasonal slowdown, according to the article published in Scientific Reports, a peer-reviewed journal published by Nature Portfolio.

Scientists from Banaras Hindu University, the Indian Institute of Tropical Meteorology and the India Meteorological Department report that the steepest annual declines have occurred in the northern interior region – particularly Amritsar and Kolkata – as well as the Himalayan belt and the west coast, particularly Mumbai.

All nine geographically diverse regions of India showed an overall annual decline in sunshine hours, although the rate of decline varied across India. The monthly analysis reveals significant increases from October to May, followed by sharp declines from June to July in six of the nine regions.

This seasonal pattern of sunshine intersects with a deeper, long-standing problem: India’s severe air pollution crisis — now among the world’s 10 most polluted countries — that scientists trace back to the 1990s. Rapid urbanization, industrial growth, and land-use changes have driven fossil fuel use, vehicle emissions, and biomass burning, sending aerosols into the atmosphere and dimming the sun’s rays.

In winter, high air pollution from smog, temperature inversions, and crop burning in the Indo-Gangetic plains produces light-scattering aerosols that reduce sunshine hours.

These aerosols—small solid or liquid particles from dust, vehicle exhaust, crop burning, and other sources—stay in the air long enough to affect sunlight, climate, and health.

In June-July, monsoon clouds cover much of India, sharply reducing sunlight, although aerosol levels are lower than in winter.

Scientists note that higher sunshine hours from October to May do not mean cleaner air; rather, they reflect more cloud-free days. Dull winter sunlight can be scattered or diffused, reducing the intensity without completely blocking the sunshine, which the instruments still record as sunshine hours.

“Our study found that the decrease in sunshine hours is associated with clouds that hang around longer without releasing rain, blocking more sunlight. These longer-lasting clouds form indirectly due to aerosols that change the weather and climate,” said Manoj Kumar Srivastava, professor of geophysics at Banaras Hindu University and one of the authors of the study.

Aerosols reduced the amount of sunlight reaching the ground in India by about 13%, while clouds accounted for an additional 31-44% drop in surface solar radiation between 1993 and 2022, according to Sachchida Nand Tripathi, an atmospheric scientist at the Indian Institute of Technology (IIT) Kanpur.

These patterns raise concerns about agriculture, daily life and India’s solar energy ambitions, while highlighting where solar panels can be most effective.

Solar power now accounts for 47% of India’s renewable energy capacity. The government says it is on track for 500 GW of renewables by 2030, with more than 100 GW of solar installed since early 2025. But dwindling sunlight could cast a shadow over the country’s solar ambitions.

According to Prof. Tripathi, air pollution is compounding the problem. It reduces solar panel production by 12-41% depending on the type of photovoltaic system – the technology that converts sunlight into electricity – and costs about $245-835 million in lost electricity production.

Studies also show that cleaner air could increase India’s annual solar energy production by 6-28 terawatt hours of electricity – enough to power millions of homes for a year.

But the impact of pollution doesn’t stop at solar energy. It also has a heavy impact on agriculture, causing about 36-50% loss in crop yields – mainly rice and wheat – in the most polluted regions of the country, according to Prof. Tripathi.

India is not alone in losing sunshine; around the world, increasing air pollution and changing weather patterns have darkened the skies.

A study published in Atmospheric Chemistry and Physics, notes that Europe likely had reduced sunlight reaching the ground due to air pollution between 1970-2009 in Germany, sunshine hours decreased by approximately 11% from 1951 to 1980 attributed to industrial gas emissions and associated cloud formation.

Research also shows that stricter clean air laws in the 1990s led to a bounce in sunny hours throughout Europe.

China also experienced a a significant decline in sunshine hours from the 1960s to the 2000s, mainly due to increased aerosol emissions from rapid industrialization. Sunshine duration varies in Chinese cities, with some areas seeing more significant declines due to factors such as air pollution.

The good news: Scientists say Earth’s surface has been gradually getting more sunlight since the 1980s, a trend known as global brightening, after decades of dimming.

A new analysis of satellite data from 1984 to 2018 appears to confirm this, showing that the effect is strongest over land and in the Northern Hemisphere, driven mainly by falling aerosols in the 1980s and 1990s and changes in cloud patterns.

The bad news: heavily polluted countries like India miss out. If the Sun continues to hide behind the smog, India risks running on fumes instead of full power.