Sensitivity of extreme climate events to CO2-induced biophysical atmosphere-vegetation feedbacks in the western United States -: art. no. L07702

We have tested the sensitivity of extreme temperature and precipitation events to CO2-induced atmosphere-vegetation feedbacks (AVFs) in the western United States using an equilibrium vegetation model coupled to a regional climate model. Biophysical AVFs resulted in positive anomalies in the frequency and magnitude of extreme temperature events over much of the western United States, with the notable exception of key high elevation areas, where there were strong negative anomalies. Anomalies in extreme temperature events were largely associated with changes in surface albedo, LAI, upper layer water extracted and root zone depth. Negative anomalies in extreme precipitation along the Pacific coast were associated with reductions in low-level specific humidity, zonal wind speeds and eddy kinetic energy. These results suggest that AVFs could strongly influence the response of extreme climate regimes to anthropogenic greenhouse forcing, with the sign of that influence varying on horizontal scales of 10(1) to 10(2) km.