Interdecadal Climate Regime Transition and Its Interaction With Climate Change in CMIP5 Simulations

Large-amplitude interdecadal shifts of atmospheric and ocean states from one climate regime to another have been observed several times in the 20th century. They include the 1976 transition from cool tropical Pacific SST to warm tropical SST and the post-1998 reversal back to a cooler state that is emerging to be potentially important for the climate outlook of the coming decades. The transition events affect not only atmospheric circulation but also global water cycle. Because on decadal-to-interdecadal time scale the amplitude of the climate shift is comparable to the trend induced by anthropogenic greenhouse gas forcing, understanding the structure, statistics, and predictability of those events is critical for near-term climate projection. Due to the small number of interdecadal transition events that are available from instrumental records, this study will deduce the statistics and predictability of the transition events by analyzing the new CMIP5 climate model simulations. The core analysis of this work will unravel the interconnection of sea surface temperature, atmospheric circulation, and global water cycle associated with the climate shift events in the CMIP5 centennial runs for the past, present, and future climate. The CMIP5 Decadal Runs for the 20th century will be analyzed to determine the predictability of the transition events using fully coupled climate models. Idealized atmospheric GCM simulations will be performed to aid the interpretation of the results from CMIP5. The results of this study will contribute to integrating decadal natural variability, climate regime transition, and anthropogenic GHG-induced climate change into a single framework for projecting multidecadal climate change.

Project Term: 
2010 to 2013
Project Type: 
University Project