Sun has not been shining much on India for nearly 40 years. Blame the government

India is losing sunshine hours, and this trend has greatly increased in the past three decades. A study done by Indian scientists shows that since 1988, the Sun's date with India has been on a downward trend, thanks to the cloud cover and the increasing number of aerosols in the air. The Banaras Hindu University, Pune-based Indian Institute of Tropical Meteorology (IITM) and the India Meteorological Department (IMD) collaborated on a study that studied data from 1988 to 2018. The monthly sunshine hours (SSH) analysis from 20 meteorological stations and from nine regions showed that the annual sunshine hours in India have been consistently declining. The research was published in the journal Nature on October 2.

The study noted that there was a "persistent decline of SSH in the Indian subcontinent on all temporal scales, excluding the north eastern region, where mild seasonal levelling off was found." Meanwhile, there was a "significant increment from October to May followed by significant drops from June to July in six regions, except the northern inland and Himalayan region that showed comparatively opposite monthly trends." Previous studies have found decreasing trends in solar radiation across India and a persistent solar dimming in the 21st century. The researchers blame this on the rising aerosol levels, which went up because of urbanisation in the early 1990s.

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India did not take timely steps to control aerosols in environment

The study notes that during the 1990s, "India’s economic growth drove urbanisation, land-use changes, and industrialisation, leading to increased fossil fuel consumption, vehicular emissions, and biomass burning." As a result, aerosol concentrations in the atmosphere rose, consequently reducing solar radiation. India was not the only country to undergo changes in the early 90s, with China and Japan also witnessing similar changes. However, the two countries implemented policies to control aerosol pollution. Beijing cracked down with the Clean Air Action Plan, while Japan successfully implemented clean technologies and emission controls. This lowered aerosol levels and caused a brightening trend, the study authors wrote.

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Cloud cover increasing because of aerosols

They added that weather conditions have also driven this change, with clouds obstructing sunlight and reducing solar radiation and sunshine hours. Aerosols are responsible for the increasing cloud cover, the study states. "As per the theory of condensation for warm cloud systems, bigger cloud droplets are formed when the natural balance of aerosols and humidity persists, and formation of perceptible clouds is achieved." However, when the number of aerosols goes up in the same amount of humidity, "a greater number of smaller-sized cloud droplets are developed and the cloud lifetime is prolonged." As a result, the hours during which the solar radiation can reach the surface would also be impacted.