Effect of Climate Change on Solar Radiation Over a Tropical Region

This study investigates the contribution of climate change to solar radiation variability over a tropical region taking the four climate regions in Nigeria as a case study. Three solar radiation components (diffuse, direct, and global solar radiation) were obtained from the database of Modern-Era Retrospective Analysis for Research and Applications, Version 2 (MERRA-2) spanning the periods of 40 years (1980 – 2020) were used for the study. The seasonal trend and change-point analyses were quantified using the Mann-Kendall test, Pettitt test, and linear regression Panalysis. Mann-Kendall trend test revealed that there were increasing trends in diffuse radiation (DF) with a maximum strength of 3.63 per year in Rainforest and Coastal regions. Meanwhile, absolute decreasing trends were detected in direct (DR) and global solar radiation (GSR) respectively across the four regions in Nigeria. Also, based on the Pettitt test, DF had a predominant change point in 1999, DR in 2005, and GSR in 2001. The maximum observable changes of 0.701 W/m
²
for DF, -3.076 W/m
²
for DR, and -1.487 W/m
²
for GSR annually over Nigeria using the slopes of linear regression. Finally, the climate was observed to contribute a maximum of 50.30% to increase in DF, 67.80% to decrease in DR, and 65.00% to decrease in GSR using the coefficient of determination. It can be inferred from this study that the current variability in solar radiation across the climate regions in Nigeria is largely caused by climate change.