Global vegetation and climate: Self-beneficial effects, climate forcings and climate feedbacks

Abstract
Vegetation strongly affects climate by influencing the exchanges of energy and moisture between the land and atmosphere. This paper uses climate modelling studies to discuss four perspectives on the influence of vegetation on climate through biophysical properties of the land surface; (i) the extent to which present-day patterns of climate are modified by the presence of vegetation, and the importance of this for the vegetation itself; (ii) anthropogenic vegetation change as a driver (forcing) of climate change; (iii) the physiological impact of elevated CO₂ on vegetation as a forcing of climate change through the surface energy budget; and (iv) the responses of vegetation to radiatively-forced climate change and resulting feedbacks on the climate change itself. Contemporary vegetation increases continental precipitation while generally reducing temperature extremes, and this is crucial for maintaining present-day global vegetation patterns. Mid-latitude deforestation has acted to cool the climate by increasing surface albedo, while continued tropical deforestation may exert a warming and reduce precipitation. Elevated CO₂ may cause a warming through reduced transpiration by plants in addition to the greenhouse warming. Forest die-back may accelerate a projected precipitation reduction in Amazonia, while expansion of the boreal forests may provide a positive feedback on local warming.