Precipitation variability over India during the 20th and 21st centuries: investigating natural and anthropogenic drivers

Changes in precipitation pattern can lead to widespread impacts across natural and human systems. This study assesses precipitation variability as well as anthropogenic and natural factors responsible for the precipitation variability over India in the twentieth and twenty-first centuries using the Coupled Model Intercomparison Project (CMIP5) and observational data sets. We specifically quantify the impact of natural (volcanic and solar radiation) (NAT), greenhouse gas (GHG), anthropogenic aerosol (AA), and land use (LU) forcings on precipitation changes over India. In the observational record, a decrease in precipitation is observed during monsoon and winter seasons, whereas an increase is noticed in pre- and post-monsoon seasons. These observed changes are likely dominated by changes to GHGs and a reduction in AA during the twentieth century compared to those of the LU and NAT forcings. Anthropogenic aerosol plays a dominant role in reducing rainfall in the summer monsoon, leading to drying trends over the second half of the twentieth century in India. The projected simulations indicate an increasing trend during the twenty-first century. The temporal and spatial variability of precipitation displays substantial changes over India during different seasons at different periods under the Representative Concentration Pathway (RCP) 2.6 and 8.5 emission scenarios. Overall, model simulations based on RCP 8.5 show increases in future precipitation throughout the twenty-first century over India.