Identifying Climate Model Biases in the Pattern of Ocean Warming and their Influence on Regional Climate Change

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Surface temperature observations in the tropical Pacific Ocean show a higher rate of warming over the last 50 years in the West Pacific than in the East Pacific. However, most state-of-the-art climate models show the opposite. It is uncertain if the observed trend will continue or if the ocean warming pattern will eventually revert to something more like climate model projections. The difference between these scenarios is a primary source of uncertainty in projected future changes in regional climate because unusual temperature patterns in the tropical oceans generate large-scale atmospheric wave disturbances that influence regional climate throughout the globe. This project will use climate modeling and analysis of climate model data to understand the causes of the discrepancy between climate models and observations in the recent pattern of ocean warming, to understand the processes that lead different climate models to project different future changes in the ocean temperature pattern, to identify regions worldwide where atmospheric circulation and precipitation projections could be affected by climate model biases in the tropical Pacific, and to understand the processes linking changes in these regions to the tropical Pacific. By combining an understanding of how the tropical Pacific Ocean changes in the future in different climate models with an understanding of how and why individual climate models are biased compared to the observational record, this research has the potential to constrain future projections of ocean warming patterns. Improved constraints on future climate change in the tropical Pacific will in turn improve constraints on future changes in atmospheric circulation and regional climate in regions such as North America that are strongly influenced by wave disturbances emanating from the tropical Pacific. The work will support the career development of an early-career researcher and a graduate student as well as include public outreach activities through the University of Washington Program on Climate Change and the Pacific Science Center in Seattle.This project bridges the gap between fundamental science questions on how and why the tropical Pacific responds to anthropogenic forcing on different timescales with the practical need for better projections of how water resources will change in the coming decades in the U.S. Southwest and other regions that are strongly influenced by El Niño. This research will also identify and investigate the causes of climate model biases, in their simulation of the current climate and their simulation of climate trends. This work will provide valuable information for climate model developers, who are working to address these biases and improve climate models, and for the large community of scientists using climate models to understand and plan for the regional impacts of climate change. This project will help train the next generation of climate scientists. The results of this project will be disseminated widely through publications, conference presentations, press releases, and outreach to the public.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.