Near-term Projection of the Indian Summer Monsoon Circulation Using CESM 1.5C, 2.0C, RCP4.5 and RCP8.5 Scenarios

The NCAR CESM low-warming simulations (1.5⁰C, 2.0⁰C), RCP4.5 and RCP8.5 scenarios are used to assess the near term (2021–2050) changes of the Indian Summer Monsoon (ISM) variability. It is demonstrated that with the increase in warming and radiative forcing likely to cause an enhanced monsoon precipitation over east Asia. In 1.5⁰C forced climate, a weak ISM circulation is projected, while for 2.0⁰C warming monsoon circulation is likely to strengthen over the north Indian Ocean and intense easterlies from the equatorial Pacific are projected. Projection from the RCP4.5 scenario is associated with strong southwesterly monsoon wind over the entire Indian Ocean to the South China Sea and an intense easterly wind from the North Pacific to east Asia. The monsoon circulation over the north Indian Ocean is likely to weaken in the RCP8.5 forced climate. In all the scenarios, SLP variability over the far North Pacific is likely to play a dominant role as an internal variability to be able to influence the ISM circulation. It is found that an increasing standard deviation of internal Variability in SLP over the far North Pacific with increasing warming. Therefore, the importance of internal climate variability in SLP over the far North Pacific is clearly seen to influence the ISM projection pattern in the warming climate. Although model systematic biases in simulation still cause great concern for climate modelers, it is recognized that climate projections are inherently uncertain because a model can never fully describe the system that it attempts to specify. It is anticipated that this analysis based on the CESM ensemble will inspire probabilistic thinking and inform planning for the summer monsoon community and related stakeholders.