Role of plant physiology and dynamic vegetation feedbacks in the climate response to low GHG concentrations typical of late stages of previous interglacials

[1] Using a version of NCAR's Community Climate System Model (CCSM3), we apply lowered greenhouse gas (GHG) concentrations (240 ppm CO2 and 450 ppb CH4) based on typical values reached during the latter stages of previous interglacials, which are not influenced by anthropogenic GHG emissions. Using these lowered GHG levels and including feedbacks both from vegetation changes produced by the dynamic vegetation model and from the plant physiological response to lowered CO2, the climate is 3.14 K cooler than in the modern control simulation. The plant physiology response alone is a small component of the total cooling globally (0.16 K), but it contributes an additional cooling of about half that caused by changes in vegetation distribution alone (0.29 K). The inclusion of plant physiology also amplifies the loss of high-latitude boreal and tropical vegetation and enhances permanent snow cover area.