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India is grappling with a dire air pollution crisis that is not only suffocating its skies but also dramatically diminishing the amount of sunlight reaching the ground. A compelling new study conducted by a team of six Indian scientists reveals that over the past thirty years, the nation has witnessed a steady decline in sunshine hours, primarily due to an alarming increase in atmospheric pollutants and changing weather patterns. This decline poses significant ramifications for agriculture, energy production, and public health.
A Study in Decline
The research, published in *Scientific Reports*, utilises data from 20 weather stations across the country, covering the period from 1988 to 2018. The findings indicate a consistent reduction in sunshine hours throughout most of India, with only the northeastern region experiencing a slight seasonal respite. The steepest declines were particularly evident in the northern inland areas, such as Amritsar and Kolkata, as well as along the Himalayan region and the west coast, including Mumbai.
The study, conducted by experts from Banaras Hindu University, the Indian Institute of Tropical Meteorology, and the India Meteorological Department, underscores a troubling trend that intersects with the country’s ongoing pollution crisis. With India now ranking among the world’s top ten most polluted nations, researchers trace this deterioration back to the 1990s, attributing it to rapid urbanisation, industrial expansion, and increased fossil fuel consumption.
The Role of Aerosols and Clouds
The winter months exacerbate the situation as smog, temperature inversions, and crop burning create a cocktail of light-scattering aerosols that further obscure sunlight. These aerosols—minute particles resulting from various sources such as vehicle emissions and agricultural activities—linger in the atmosphere long enough to significantly impact solar radiation and, consequently, health and climate.
During the monsoon period, from June to July, dense cloud cover also greatly diminishes the sunlight reaching the Earth despite a reduction in aerosol concentration. Interestingly, while more sunshine hours are recorded from October to May, this does not necessarily signify cleaner air; rather, it reflects a higher number of cloud-free days. Manoj Kumar Srivastava, a geophysics professor at Banaras Hindu University and a lead author of the study, notes that these persistent clouds are formed as a result of the very aerosols that impede sunlight.
The data indicates that aerosols have reduced sunlight at the ground level in India by approximately 13%, while cloud cover has contributed to an additional 31-44% decrease in solar radiation from 1993 to 2022, according to atmospheric scientist Sachchida Nand Tripathi from the Indian Institute of Technology Kanpur.
Implications for Energy and Agriculture
The implications of diminishing sunlight extend beyond mere aesthetics; they threaten India’s agricultural output and renewable energy ambitions. Solar energy currently accounts for 47% of the country’s renewable energy capacity, and the government aims for a staggering 500GW of renewable energy by 2030, with over 100GW of solar capacity already installed as of early 2025. However, the decline in sunshine hours could hinder these solar aspirations significantly.
Prof. Tripathi highlights that air pollution not only leads to reduced solar panel efficiency—by 12-41% depending on the photovoltaic technology—but also results in an estimated loss of $245-835 million in power generation. Moreover, cleaner air could potentially increase India’s annual solar energy production by an additional 6-28 terawatt hours, enough to power millions of homes for an entire year.
The toll on agriculture is equally concerning, with crop yields, particularly for rice and wheat, suffering an estimated loss of 36–50% in the country’s most polluted regions.
A Global Perspective
India is not alone in this struggle; the global landscape is similarly marred by rising air pollution and shifting weather patterns that obscure sunlight. Data from Europe indicates that air pollution reduced sunlight exposure between 1970 and 2009, with Germany experiencing an 11% decrease in sunshine hours from 1951 to 1980. Conversely, stricter clean-air regulations in the 1990s led to a resurgence of sunshine hours across the continent.
The good news is that worldwide, there has been a gradual increase in sunlight since the 1980s—a phenomenon termed “global brightening.” However, this trend is not universally experienced, as heavily polluted nations like India continue to suffer under a veil of smog, missing out on the sunlight that could empower their renewable energy initiatives.
Why it Matters
The ongoing decline in sunshine due to air pollution in India is not merely an environmental issue; it poses serious threats to the nation’s food security, energy independence, and public health. As the country strives for ambitious renewable energy goals and works to combat climate change, addressing air quality and the factors contributing to reduced sunlight will be crucial. Without concerted efforts to clear the air, India risks not only its solar future but also the well-being of its citizens and the sustainability of its agricultural systems.
