Study Finds Sharp Decline in India’s Sunshine Hours Over Three Decades

A new study published in Nature’s Scientific Reports reveals that India’s sunshine hours have been consistently declining over the past 30 years. The research was conducted by scientists from Banaras Hindu University (BHU), the Indian Institute of Tropical Meteorology (IITM), and the India Meteorological Department (IMD).

Sunshine Decline Across Regions

• North Indian Plains: Steepest decline, with sunshine hours dropping by 13.1 hours per year.
• West Coast: Average reduction of 8.6 hours per year.
• Northeast India: Only region showing a marginal seasonal ‘levelling off’ in decline.
• Monsoon Months (June–September): Sharpest reduction in sunshine hours.
• Dry Months (October–May): Slight increase observed.

Causes of ‘Solar Dimming’

• Scientists attribute the trend to rising aerosol concentrations and increased cloud cover.
• Aerosols — tiny particles from industrial emissions, biomass burning, and vehicular pollution — act as condensation nuclei, forming smaller and longer-lived cloud droplets.
• This leads to more persistent cloudiness, reducing the amount of sunlight reaching the Earth’s surface.

Implications

• The decline in sunshine hours has significant impacts on:
  • Solar energy generation, reducing potential output.
  • Agricultural productivity, affecting crop growth dependent on sunlight.
  • Climate modelling, as reduced solar radiation alters local temperature and weather patterns.