On the present and future teleconnection to the Indian summer monsoon in CMIP6 models

In a continuing warming climate, it is necessary to understand how the Indian summer monsoon (ISM) will respond to El Nino Southern Oscillation (ENSO) and other dominant Non-ENSO climate patterns. Using several coupled climate models participated in the CMIP6 simulations, we show that the frequency of droughts and floods is similar in these models either in the historical or future scenarios (ssp126, ssp245, ssp370, ssp585). This symmetry is unlike the observation where droughts are more frequent and vigorous than floods. We show that while the number of ENSO years is projected to increase with raised CO2 forcings, the fraction of ENSO and Non-ENSO years experiencing extremes of ISM remain relatively constant. However, the future scenarios indicate more frequent La Nina-related floods than the historical period. We show that most models do not capture the observed spatial maps of vertically integrated moisture flux during Non-ENSO ISM extreme years. While in the observation, a stronger role is played by the climate of the Arabian Sea and West Asia, most models are driven by the climate of the western North Pacific Ocean during non-ENSO ISM extremes. Our results indicate changes in the future teleconnection pattern during Non-ENSO related ISM extremes. These results call for special attention for model diagnosis and development for a better seasonal prediction.