Simulated responses of potential vegetation to doubled-CO2 climate change and feedbacks on near-surface temperature

Increases in the atmospheric concentration of carbon dioxide and associated changes in climate may exert large impacts on plant physiology and the den sity of vegetation cover. These may in turn provide feedbacks on climate th rough a modification of surface-atmosphere fluxes of energy and moisture. T his paper uses asynchronously coupled models of global vegetation and clima te to examine the responses of potential vegetation to different aspects of a doubled-CO2 environmental change, and compares the feedbacks on near-sur face temperature arising from physiological and structural components of th e vegetation response. Stomatal conductance reduces in response to the high er CO2 concentration, but rising temperatures and a redistribution of preci pitation also exert significant impacts on this property as well as leading to major changes in potential vegetation structure. Overall, physiological responses act to enhance the warming near the surface, but in many areas t his is offset by increases in leaf area resulting from greater precipitatio n and higher temperatures. Interactions with seasonal snow cover result in a positive feedback on winter warming in the boreal forest regions.