Abdul Wahab Khan Panaji
Goa’s sunshine is quietly losing ground, with a study indicating that the amount of sunlight reaching the Earth’s surface over the west coast, including Goa, has been declining for three decades.
The research, published in Scientific Reports (Nature Portfolio) in October 2025, analysed sunshine hour trends from 1988 to 2018 across 20 stations in nine geographically diverse regions of India, and claimed “solar dimming” across the subcontinent.
The findings indicate that the west coast region, which includes Goa, Thiruvananthapuram and Mumbai, showed an annual decline of 8.62 hours per year – among the highest rates recorded nationally. For Goa specifically, the study documented maximum sunshine of approximately 290 hours per month and a minimum of about 57 hours per month, with seasonal variations influenced by monsoon patterns.
Although the study does not isolate Goa as a standalone station, it analyses the west coast region, which includes coastal stations climatically representative of Goa.
Annual trend analysis using Mann–Kendall statistics and Sen’s slope estimator shows a significant decline of -8.62 sunshine hours per year along the west coast between 1988 and 2018. For the west coast specifically, the study found maximum sunshine during winter season at 727 hours, followed by pre-monsoon at 712 hours, with minimum values during post-monsoon at 398 hours.
This translates into a cumulative loss of more than 250 sunshine hours over three decades, even in regions traditionally considered solar-rich.
The intra-annual anomaly plots further reveal that the highest sunshine magnitudes occurred before 2005, after which negative anomalies became more frequent. “A steady and consistent negative anomaly… was observed,” the authors note, adding that recent positive years still fall short of earlier averages.
Comparing Goa’s situation with other regions reveals varying patterns of decline across India’s diverse geography.
The authors caution that the decline is not driven by cloud cover alone. The study highlights the role of aerosol-cloud interactions, noting that “hygroscopic aerosols, acting as cloud condensation nuclei, prolong cloud lifetime,” thereby reducing the duration for which solar radiation reaches the ground. This aerosol indirect (Twomey) effect is particularly relevant for coastal belts such as the west coast, where humidity levels amplify aerosol impact on cloud microphysics.
According to the researchers, the study underscores the critical role of weather conditions in assessing solar energy potential.
The study has been conducted by researchers Arti Choudhary, Bharat Ji Mehrotra and Manoj K Srivastava from Banaras Hindu University’s Institute of Science, alongside Atul K Srivastava from the Indian Institute of Tropical Meteorology, V K Soni from the India Meteorological Department and Pradeep Kumar from Manipal University, Jaipur.
