India’s skies have been quietly dimming. This year’s unbroken grey monsoon made many feel the sun had gone into hiding. Now a new scientific study confirms the worry: measured sunshine hours across almost all of India have been steadily falling over the past 30 years.
Researchers from Banaras Hindu University, the Indian Institute of Tropical Meteorology, and the Meteorological Department analysed data from 1988 to 2018. They found that every region except the far northeast saw declines in the annual “sunshine hours”, the hours when sunlight is strong enough to register on instruments.
In practical terms, India is losing many hours of bright daylight each year, a trend the scientists call a long-term “solar dimming”.
Fewer Sunlit Hours Across India
Data from 20 weather stations spanning nine regions make the picture clear: sunshine hours are dropping almost everywhere. On average, the west coast of India loses about 8.6 hours of sunshine per year, while the northern plains lose around 13.1 hours per year, the steepest decline of all.
Other parts of India also see losses: the east coast about 4.9 hours per year, the Deccan plateau 3.1 hours, and the central inland region 4.7 hours. Only the northeast showed a very minor change, a slight “levelling off” in monsoon sunlight.
Over the decades, these losses add up. For example, a drop of 13 hours per year in the northern plains means roughly two weeks less bright sun every decade.
Sunlight has also shifted with the seasons. The researchers found sunshine hours climbed during the dry winter-spring months (October to May) but fell sharply in the summer monsoon (June to September). In other words, India’s already cloudy monsoon is now even cloudier.
As one scientist noted, days without rain were often overcast this year, especially on the west coast, central India, and the Deccan plateau. Even when it wasn’t raining, haze and humidity kept the sky a uniform grey.
This reinforces that the long-term trend is no fluke; the same haze and moisture patterns seen today already existed in the data and appear to be intensifying.
Winners And Losers In The Sky
The dimming is not uniform. Some areas saw steeper sunshine losses than others. The north Indian plains, Punjab, Haryana, Uttar Pradesh, and Delhi, bore the worst decline, over 13 hours per year. In these densely farmed and industrialised regions, polluted air often traps moisture, leading to foggy winter mornings.
On the west coast, Mumbai, Goa, and Kerala, the drop was around 8.6 hours per year, likely reflecting heavy shipping pollution and coastal cloudiness. The Bay of Bengal coast lost about six hours per year, the Himalayan foothills about nine, and even India’s island locations saw five to six hours lost annually.
In contrast, the northeast of India shows only a tiny annual decline and even a seasonal “levelling off” in monsoon sunshine.
The takeaway is that no major region in India is getting more sun, and many are getting noticeably less. This has knock-on effects: for example, places famed for sunshine and solar panels are now seeing more shade.
It also helps explain why people across the country, from farmers in central India to office workers in Delhi, have commented on gloomier skies.
The Science Of Solar Dimming
Why is this happening? The answer lies in pollution and clouds. Tiny airborne particles known as aerosols, soot, dust, smoke, and chemicals from factories, vehicles, burning crops, and other sources have increased over India during rapid economic growth. These particles change how clouds behave.
As meteorologist Manoj Srivastava explains, “These aerosols act as condensation nuclei, creating smaller and longer-lived cloud droplets that keep skies overcast for extended periods.”
In simple terms, more aerosols seed clouds with millions of tiny droplets instead of fewer big drops. Those small droplets don’t coalesce into rain as quickly, so clouds linger longer and reflect sunlight away from the ground. The result is a whiter, thicker cloud cover that shades the land for more hours.
This “Twomey effect” of aerosols is well known in atmospheric science. For India, decades of forest fires, crop burning, and rising industry mean aerosol levels have stayed high, unlike countries such as Japan or China after 2010 that cleaned up their air and saw skies brighten.
In fact, researchers point out that since the 1990s, India’s economic boom has sent up soot and pollution, reducing the amount of sunlight reaching Earth. This scientific picture fits the observed trend: as aerosols grew, sunlight hours fell. It also matches this year’s experience, when air quality was poor during the monsoon, the clouds hung persistently overhead even on dry days.
Energy Implications
India has one of the world’s fastest-growing solar power sectors, but dimming sun could undercut those gains. Every photovoltaic panel needs a certain amount of strong sunlight to reach peak output.
With fewer sunny hours, actual energy generation can fall short of expectations. The study’s authors warn that reduced solar incidence could affect power output and long-term planning for renewable infrastructure. In practical terms, a solar farm forecast to produce a gigawatt-hour might lose several per cent of its generation each year if the sun is frequently blocked.
Investors and grid planners are taking note. They now see that the rules of the game are shifting: models and yield forecasts must factor in India’s dimming trend. When mapping out future projects and supply targets, engineers can no longer assume as many sunny days as in the 1990s.
There may also be technical responses, installing panels at higher altitudes (above smog), using dual-axis trackers, or mixing solar with wind or storage to hedge against cloudy periods. At the very least, this study suggests that policy-makers should push even harder on cleaning the air, something that would brighten the sky and boost solar output simultaneously.
Also Read: Plaster Of Paris Ganesh Idols: Vishakhapatnam’s Environmental Destruction
Farming And Climate Modelling
The loss of sunlight touches agriculture, too. Farmers rely on ample sunlight for crops to grow, especially in the cooler seasons outside the monsoon. If daylight weakens, some crops could yield less or require longer to ripen.
Although heavy monsoon rains are welcome, scientists caution that too many grey days in a row can slow plant growth. In broad terms, sunlight fuels photosynthesis, so a sustained dip in sunshine hours could tighten the energy available to crops.
Moreover, climate and weather forecasters use sunlight data in their models. A steady drop in sun exposure means model inputs must be updated. Rainfall and evaporation patterns are sensitive to the amount of solar heating.
If models assume normal sun levels but the air stays hazy, they may mispredict local temperatures or drought risk. The researchers explicitly note that the declining sun hours have major implications for climate modelling.
This implies that agricultural planning, from sowing dates to irrigation schedules, might need revision. Governments and farmers may eventually adapt by shifting crop calendars, using shade-tolerant varieties, or improving greenhouse designs.
Human And Health Impacts
Less sunshine also affects people’s well-being. Psychologists note that prolonged cloudy weather can disrupt our mood and health. For example, reduced sunlight in winter months is linked to seasonal affective disorder, a type of depression caused by disturbed circadian rhythms.
During periods of low sun exposure, the body keeps producing melatonin (the sleep hormone) and lowers serotonin, which can trigger lethargy or sadness. In India, where monsoon clouds already bring a “monsoon blues” for some, an intensifying overcast trend could make those mood swings more common.
Vitamin D is another concern. Dubbed the “sunshine vitamin,” it is produced in our skin via ultraviolet rays. Doctors warn that less sun means more risk of vitamin D deficiency.
Even before the dimming trend, many Indians had low vitamin D levels despite living in a sunny country; now the problem could worsen. This has knock-on health effects, from weaker bones to poorer immune function.
Public health experts may need to encourage alternative vitamin D sources, diet, supplements, or artificial UV lamps, especially for children and indoor workers during extended cloudy spells.
Every day life also loses some brightness. Tourism, architecture, and even mood are subtly shaped by sunlight, and its loss could make our cities feel gloomier in more ways than one.
What To Do About The Dimming Sun
The study’s findings make it clear: India’s sun is indeed “missing” a bit each year, stolen by thicker clouds and pollution. But there are solutions. Experts point out that the most straightforward fix is cleaning up the air.
Past experience shows that cutting aerosol emissions lets the sun shine through. China and Japan saw their skies brighten once they enforced strong air quality laws. In India, this means stricter controls on industrial smoke, traffic fumes, and crop burning.
Beyond that, policy-makers and planners have work to do. Renewable energy forecasts and infrastructure plans should be updated to reflect lower solar input. Farming policies might promote crops that can tolerate less light, or adjust water and fertiliser use. Public-health campaigns can raise awareness about vitamin D and mental health during long monsoons.
In short, this dimming trend is a call to action for students, citizens, and analysts alike. It touches energy security, agriculture, climate strategy, and wellbeing. On a hopeful note, the trend is reversible.
If India curbs its pollution and continues improving forecast models, the sun could yet regain its place in the sky, proving that even a disappearing act is something people can correct when science illuminates the problem.
Images: Google Images
Sources: Firstpost, The Times of India, Hindustan Times
Find the blogger: Katyayani Joshi
This post is tagged under: solar dimming, india climate change, sunshine hours decline, bhU study, iitm research, imd findings, air pollution india, aerosol pollution, solar energy india, renewable energy, clean air initiative, sustainable development, monsoon clouds, indian environment, solar power future, agriculture impact, climate policy india, mental health awareness, vitamin d deficiency, urban living india, public health india, environmental research, climate action, green india, energy transition, global warming effects, indian monsoon, weather patterns, atmospheric science, science communication
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