Terrestrial processes influence the atmosphere by controlling land surface fluxes of energy, water, and carbon. Prior research has demonstrated that parameter uncertainty drives uncertainty in land surface fluxes. However, the influence of land process uncertainty on the climate system remains underexplored. Here, we quantify how assumptions about land processes impact climate using a perturbed parameter ensemble for 18 land parameters in the Community Earth System Model (CESM2) under preindustrial conditions. We find that an observationally informed range of land parameters generate biophysical feedbacks that significantly influence the mean climate state, largely by modifying evapotranspiration. Global mean land surface temperature ranges by 2.2°C across our ensemble, and drives spatially variable changes in precipitation. Notably these spatial patterns differ from those driven by radiative warming through increases in atmospheric CO2. Our analysis demonstrates that land parameter uncertainty propagates to the entire Earth system, and provides insights into where and how land process uncertainty influences climate.
Authors: Claire M. Zarakas1, Daniel Kennedy2, Katherine Dagon2, David Lawrence2, Amy Liu1, Gordon Bonan2, Charles Koven3, Danica Lombardozzi2, Abigail L. S. Swann1,4
1Department of Atmospheric Science, University of Washington, USA 2National Center for Atmospheric Research, USA 3Lawrence Berkeley National Laboratory, USA 4Department of Biology, University of Washington, USA