The centrality of projected climate variables to the discourse of studying, attributing and planning for climate change

Abstract:

The centrality of projected climate variables to the discourse of studying, attributing and planning for climate change is well established. It is reported widely that the uncertainty in climate model data and the scarce availability of quality observed data constrains the analysis of climate variables. Consequently, the ambiguity in effect of climate change on precipitation is well reported. In this work we address this gap by studying the behaviour of projected (2016-2099, RCP 4.5 and 8.5) precipitation across India from high resolution (0.5⁰ x 0.5⁰) Coupled Model Intercomparison Project 5 (CMIP -5) ensemble dataset. A basic analysis of projected annual precipitation shows that under the RCP 8.5 scenario the volume of rainfall increases across most parts of India (central and western India). 53% grids show increasing trend in RCP 4.5 scenario while this goes up to 77% grids for RCP 8.5 scenario. 64% grids show an increase between 0-16% while another 23% grids show an increase in the range of 16-22% in RCP 8.5 scenario. Further the seasonal variation in precipitation was also studied. While pre monsoon precipitation shows selective decrease post monsoon precipitation shows ubiquitous increase. The monsoon precipitation expectedly reflected the trends in annual precipitation. The winter rainfall shows both increasing and decreasing trends. In conformity to international standards the precipitation indices (Simple Daily Intensity Index (SDII), Consecutive Dry Days (CDD) , Consecutive Wet Days (CWD)) were also studied. CDD show decreasing trends in the western, southern and some north-western parts of the country under both the scenarios. 39% grids and 32% showed statistically significant decreasing trend in RCP 4.5 and RCP 8.5 respectively. For CWD around 15% grids show increasing trends in RCP 4.5 scenario while 28% grids show increasing trend in RCP 8.5 scenario. For SDII while 21% of grids show an increasing trend in SDII under the RCP 4.5 scenario, 61% grids show increasing trend under the RCP 8.5 scenario. This study establishes the overall increasing trend in volume and intensity (increasing SDII in RCP 8.5) of projected precipitation in India while capturing increasing temporal homogeneity (decreasing CDD) and spatial variability.