Coupled PPE model output - land parameter impacts on the mean climate state

Terrestrial processes influence the atmosphere by controlling
land-to-atmosphere 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 biogeophysical 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
(standard deviation = 0.5°C) and precipitation changes were significant
and spatially variable. Our analysis demonstrates that the impacts of land
parameter uncertainty on surface fluxes propagates to the entire Earth
system, and provides insights into where and how land process uncertainty
influences climate.