How air pollution is stealing India’s sunshine

India is losing sunshine.

A new research Six Indian scientists have found that over the past three decades, sunshine hours (when direct sunlight reaches the Earth's surface) have been steadily declining across much of India due to clouds, aerosols and local weather.

According to a paper published in Scientific Reports, a peer-reviewed journal published by Nature Portfolio, data from 20 weather stations from 1988 to 2018 show a steady decline in sunshine hours across the country, with only the northeastern region experiencing a moderate seasonal respite.

Scientists from Banaras Hindu University, the Indian Institute of Tropical Meteorology and the India Meteorological Department report that the sharpest annual decline occurred in the northern interior region, especially Amritsar and Kolkata, and along the Himalayan belt and the west coast, especially Mumbai.

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

This seasonal pattern of sunlight intersects with a deeper, longer-standing problem: India's severe air pollution crisis (now one of the world's 10 most polluted countries), which scientists date back to the 1990s. Rapid urbanization, industrial growth and land use changes have led to increased use of fossil fuels, vehicle emissions and biomass burning, releasing aerosols into the atmosphere and dimming the sun's rays.

During winter, severe air pollution due to smog, temperature inversions, and crop burning in the Indo-Gangetic plains produces light-scattering aerosols that reduce sunshine hours.

These aerosols—tiny solid or liquid particles from dust, vehicle exhaust, crop burning and other sources—linger 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 more hours of sunshine from October to May does not mean cleaner air; rather, they reflect more cloudless days. Hazy winter sunlight can diffuse or disperse, reducing intensity without completely blocking the sunlight that instruments still register as sundials.

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

Aerosols have reduced the amount of sunlight reaching the ground in India by about 13%, while clouds have been responsible for an additional 31-44% decline in ground-level 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, everyday life and India's solar energy ambitions, while highlighting where solar panels can be most effective.

Solar power currently accounts for 47% of India's renewable energy capacity. The government says it will reach 500 GW of renewable energy by 2030, with more than 100 GW of solar installed by early 2025. But dwindling sunlight could cast a shadow over the country's solar ambitions.

According to Prof. Tripathi, air pollution is exacerbating the problem. This reduces solar panel output by 12% to 41% depending on the type of photovoltaic system (the technology that converts sunlight into electricity) and costs an estimated $245 million to $835 million in lost power generation.

Research also shows that cleaner air could increase India's annual solar energy production by 6 to 28 terawatt-hours of electricity—enough to power millions of homes for a year.

But the impact of pollution is not limited to solar energy. It is also taking a heavy toll on agriculture, causing an estimated 36-50% loss in crop yields (mainly rice and wheat) in the most polluted regions of the country, Prof Tripathi said.

It's not just India that's losing sunshine; Around the world, rising air pollution and changing weather patterns have darkened the skies.

A study published in the journal Atmospheric Chemistry and Physics, note that between 1970 and 2009, Europe likely saw a decrease in the amount of sunlight reaching the ground due to air pollution. In Germany, sunshine hours decreased by approximately 11% from 1951 to 1980, which is associated with emissions of industrial gases and associated cloud formation.

Research has also shown that stricter clean air laws in the 1990s have led to rebound in the sun hours throughout Europe.

China also experienced significant reduction during sunny hours from the 1960s to the 2000s, primarily due to increased aerosol emissions resulting from rapid industrialization. Sunlight duration varies in Chinese cities, with some areas seeing larger declines due to factors such as air pollution.

Good news: Scientists say that since the 1980s, the Earth's surface has gradually begun to receive more sunlight, a trend known as global brightening, after decades of darkness.

New analysis satellite data the period from 1984 to 2018 appears to confirm this, showing that the effect is strongest over land and in the northern hemisphere, driven mainly by aerosol deposition in the 1980s and 1990s and changes in cloud structure.

The bad news is that highly polluted countries like India are missing out on this opportunity. If the Sun continues to hide behind smog, India risks running on smoke instead of full power.