P2C2: Constraining the Physics that Regulate Equilibrium Climate Sensitivity through Simulation of Last Glacial Maximum (LGM) and Eocene Paleoclimates

This project seeks to investigate the causes and magnitude of Earth’s equilibrium climate sensitivity (ECS). The goal of the proposed project is twofold: (1) to use paleoclimate reconstructions of past cold and warm climates, the Last Glacial Maximum (LGM) and Early Eocene, to constrain ECS and its state dependence in the Community Earth System Model (CESM) series including the latest CESM2, and (2) to provide a comprehensive mechanistic understanding of the physics that govern past and future ECS. The proposed work will include development of new LGM and Eocene simulations using CESM2 and comparison of ECS in CESM2 simulations with existing LGM and Eocene simulations performed with earlier versions of the model (CESM1.2. and CCSM4) that have very different physics packages. Each simulation will be judged against a synthesis of proxy data and a new paleoclimate reanalysis product in order to evaluate the performance of the CESM versions and to identify the best estimate of ECS. The researchers will analyze this suite of simulations using climate feedback decomposition and radiative locking techniques to investigate the physical processes that regulate ECS under LGM, present, and Eocene conditions. The potential Broader Impacts include model simulations of the LGM and Eocene that would be made publicly available for the broad paleoclimate community for further investigation and model-data comparisons. Other Broader Impacts include outreach activities planned in collaboration with the Earth Camp Program (University of Michigan) to develop a hands-on climate learning module at Camp Davies Field station with the aim to broaden participation of underrepresented minority students in the Earth Sciences. In addition, the project will support the training of an early career scientist (Post-doctoral researcher). 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.