Biogeophysical effects from land-cover changes in Europe in a regional climate model

Changes in vegetation are known to have an impact on climate via biogeophysical effects such as changes in albedo and heat fluxes. The magnitude and extent of these effects is however uncertain. Here the effects of maximum afforestation and deforestation are studied over Europe. This is done by comparing three regional climate model simulations: one with present day vegetation, one with maximum afforestation and one with maximum deforestation. In general afforestation leads to more evapotranspiration (ET) which leads to decreased temperature, while deforestation leads to less ET which leads to increased temperature. There are exceptions, mainly in regions with little water available for evapotranspiration. In such regions ET will not change even if vegetation changes. In such regions changes in albedo are relatively more important for temperature. The biogeophysical effect on seasonal mean temperature is 0.5-3 °C, which is comparable to greenhouse gas forcing. The effect on seasonal extreme temperature (minimum and maximum) is larger than on mean temperature. Increased (decreased) mean temperature leads to an even larger increase (decrease) in maximum (minimum) temperature. The effect on precipitation is found to be small. Two additional simulations where vegetation is only changed in half of the domain were also performed. These simulations show that the climatic effects from changed vegetation are local. The results imply that vegetation changes have had and will have a significant impact on local climate, therefore these effects from vegetation change should be taken into account when simulating past, present and future climate. The results also imply that vegetation changes could be used to mitigate local climate change.