Projected changes and implications of surface ozone pollution in India under changing climate and emission scenarios

Surface ozone (SurfO₃) pollution poses significant challenges to air quality, public health and agriculture worldwide. In a scenario of rising anthropogenic emissions, increasing temperature and altered atmospheric compositions exacerbate SurfO₃ production in hotspots of pollution, leading to an ozone-climate penalty that could offset gains from emission reduction measures. This study explores projected changes in SurfO₃ under the Aerosol and Chemistry Model Intercomparison Project (AerChemMIP) simulations of the Coupled Model Intercomparison Project phase-six (CMIP6), focusing on their implications for agriculture in India. We analyse the simulations from the United Kingdom Earth System Model version1 at low (-LL) resolution (UKESM 1-0-LL) and Geophysical Fluid Dynamics Laboratory Earth System Model version 4 (GFDL-ESM 4) models, following the anthropogenic emission trajectory of the shared socio-economic pathway (SSP)3–7.0 high emission scenario with pre-defined climate (SSP370pdSST) and changing climate (SSP370SST). Climate-induced increases in SurfO₃ is observed in the rabi (December–February) and late-kharif (October–November) seasons, whereas early to mid-kharif (June–September) season show a reduction in SurfO₃ in India. Increasing trend in climate change-induced SurfO₃(0.03–0.08 ppbv yr^-1) is evident in the Indo-Gangetic Plain (IGP), the ‛breadbasket of India’, during most seasons, and in central India during post-kharif and rabi seasons. This suggests that, even if the precursor emission remains at the current level, climate change alone could contribute to the increase in SurfO₃ in the highly polluted regions of south Asia by 2050. Furthermore, the IGP region, one of the most fertile agricultural regions in South Asia, is likely to face significant challenges due to increasing SurfO₃, which exacerbates crop yield losses, particularly for rabi wheat. This situation is concerning, as IGP comprises of about 27% of the total cultivated area and contributes significantly (about 50% of the total food consumed in the country) to the national agricultural production in India. Therefore, the study emphasise the need for targeted mitigation strategies, particularly for CH₄, VOCs and NO_x, to mitigate the dual challenges of climate change and SurfO₃ pollution.

Keywords: Surface ozone, Climate change, AerChemMIP, Ozone-climate penalty, Agriculture, IGP