Temperature and rainfall extremes change under current, 1.5°C, 2.0°C and 3.0°C global warming across Indian climate zones

Abstract Global mean surface temperature is projected to rise by about 4°C by end of century compared to pre-industrial levels when following the most extreme scenario of greenhouse gas emissions pathway. With this rise in global temperature there is a lot of uncertainty on how weather and climate extremes would unfold, especially for various climatic zones of India. It is therefore essential that the potential changes in terms of both magnitude and direction of weather and climate extremes at regional level when global temperature reaches to different warming levels from 1°C to 3°C be established to allow for informed policy formulation. The present study explores the potential changes in the Expert Team on Climate Change Detection and Indices of rainfall and temperature estimated from the CMIP5 multi-model ensemble over different climatic zones of India at 1°C, 1.5°C, 2°C, 2.5°C and 3°C global temperature rise relative to pre-industrial levels under two Representative Concentration Pathways, RCP-4.5 and RCP-8.5. Projected changes in temperature extremes are showing significant changes at all warming levels across the nine climatic zones of India. For India country average at 3°C warming under the RCP-8.5 scenario, ensemble median shows that Warm Spell Duration Index will increase by 131 days; hot days and warm nights increase by 44% and 52% respectively; cold days and cold nights decrease by 10% and 13% relative to pre-industrial levels. The greatest changes in temperature based indices are projected in the colder northern parts of the country followed by the arid zone. Ensemble median for rainfall indices show an increase in high precipitation indices with large model spread indicating the large uncertainties in the projections. Annual total precipitation and heavy rainfall related extreme indices show statistically significant increases in tropical, temperate and semi-arid regions of India, moving from 1°C to 3°C warming level under RCP8.5 scenario whereas there is generally no significant change in the maximum number of consecutive dry and wet days. Moreover, the potential changes in climate extremes at regional level are expected to have far reaching impacts on social and economic statuses of the respective climate zones. This information at regional scale also calls attention to the national and state action plan on climate change and adaptation to be more responsive in order to take coherent and integrated policy decisions.