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The Mechanisms of Natural Variability and its Interaction With Anthropogenic Climate Change

Funding Program Area(s)
Project Type
University Grant
Project Term
to
Project Team

Principal Investigator

The objectives of this project are to come to a better understanding of certain aspects of natural variability in the climate system, and how such natural variability interacts with and/or may be differentiated from structural changes in the climate system that might arise with global warming. We propose to address whether and how the North Atlantic Oscillation, and its relatives, the zonal index and the annular modes, might undergo a secular change as a consequence of global warming. Relatedly, we shall address how such a change might be distinguished from natural variability on the decadal to multi-decadal timescale, and what processes do robustly give rise to variability on those timescales. These processes may originate in the ocean, and here we propose to investigate the mechanisms underlying this variability, and in particular if mesoscale eddies in the ocean affect or enhance the variability on decadal and longer timescales. Finally, and linking the above phenomena, we will investigate whether and how such oceanic variability will affect the atmospheric phenomena mentioned above on long timescales. Better understanding of these fundamental issues is a necessary step in understanding whether comprehensive climate models are simulating the phenomena properly and whether their results and predictions are robust. To perform this research we shall use comprehensive coupled climate models in combination with simpler, more idealized models of the climate system. Simpler models may be used to expose and analyze mechanisms, and hence to aid understanding at a fundamental level. However, their idealizations mean that they cannot easily be compared to observations and they sometimes may have unrealistic behavior. Comprehensive models have a complementary set of advantages and disadvantages: they give the most complete and realistic simulations of the climate system, and the most reliable quantitative predictions of global warming. However, their complexity often obscures the underlying processes and hinders understanding, and these models too can sometimes behave unrealistically. Thus, we propose to use the two classes of models to try to understand the phenomena and to translate that understanding into possible improvements of the comprehensive models. The benefits of the project would be an improved understanding of the mechanisms of climate variability and its interaction with global warming, as well as a better sense of whether our predictions with comprehensive models are robust and of what is needed to improve our comprehensive models. The PI on this project is Geoffrey K. Vallis of Princeton University. The PI will collaborate with Dr. Tom Delworth of NOAA’s Geophysical Fluid Dynamics Laboratory, the leader of Climate Change and Variability Group where comprehensive model simulations are performed. A single proposal is submitted through Princeton University.