Solar activity, rainfall variability and climate resilience over Bengaluru, India: A multi-timescale observational analysis

Abstract

Solar variability is a natural component of the Earth–Sun system and provides a measurable external source of atmospheric variability. Its contribution to regional climate, however, is difficult to distinguish from internal atmospheric variability and anthropogenic forcing. The present study examines the temporal relationship among solar activity, rainfall and temperature over Bengaluru, India,usingthe2005–2020periodfortheprincipalregionalanalysisandlonger records for climatic context. Solar-flux observations from 2004–2024 show the characteristic approximately 11-year solar-cycle modulation, including the weak maximum of Solar Cycle 24 and the subsequent rise of Solar Cycle 25. Annual solar-flux values for 2005–2020 peak around 2014, whereas rainfall exhibits substantial inter annual variability without a statistically significant monotonic trend (Z =0.4809, p =0.6306). Temperature shows a contrasting statistically significant increasing trend (Z =4.0963, p < 0.001), while solar flux has no significant monotonic trend (Z = 0.0550, p = 0.6778). The contrasting temporal behaviour indicates that the observed regional warming can not be attributed simply to a secular increase in solar activity. The rainfall record shows periods of enhanced and reduced variability occurring across different phases of the solar cycle, providing scope for further investigation of possible lagged solar–rainfall coupling. The results emphasise the need to distinguish solar-cycle variability from regional hydroclimatic variability and longer-term warming. The findings have broader relevance to climate resilience, particularly in relation to water security, resilient urban development and climate action under SDGs 6, 11 and 13.