Ensemble projection of global isoprene emissions by the end of 21st century using CMIP6 models

Abstract Isoprene is a key biogenic volatile organic compound of vital importance for global climate change and air quality. Previous studies projecting future changes of isoprene emissions showed a wide range of uncertainties due to the discrepancies in emission schemes, climate models, and future scenarios. Here, we use an ensemble of models from the Coupled Model Intercomparison Project version 6 (CMIP6) to explore the spatiotemporal variations of global isoprene emissions at present day and their changes by the end of 21st century. At present day, most models predict similar emission rates of 400 Tg C yr-1 but with large differences in the long-term trends. For models using the scheme of Model of Emissions of Gases and Aerosols from Nature, isoprene emissions show limited changes during historical period but significant enhancements after the year 2000. However, for models using another scheme with strong CO2 inhibition effects, isoprene emissions show decreasing trends during historical period and moderate increasing trends after the year 2000. By the end of 21st century, the ensemble projection shows increases of 21-57% in isoprene emissions with the largest enhancement for the strongest warming scenario. Attribution shows that temperature is the dominant driver for the increase of isoprene emissions, no matter whether the CO2 inhibition effects are considered or not. The enhanced isoprene emissions increase the risks of ozone pollution in a warmer climate.