Influence of the temperate and boreal forests on the Northern Hemisphere climate in the Meteo-France climate model

A temperate and boreal deforestation experiment has been performed at Meteo-France using the ARPEGE climate model. A first simulation was performed as a control with a present-day vegetation map, and another one with all forests north of 45 degrees N replaced by meadows. Prescribed monthly mean climatological SSTs were used in both integrations. The ARPEGE climate model includes a physically based land surface scheme, which has been tested both on snow-free and snow-covered sites, and has a relatively high horizontal resolution. Results of the 4-year integrations suggest that forests exert a strong influence on the surface climate of the temperate and boreal regions. Deforestation induces a significant cooling which modifies the atmospheric circulation simulated in the high latitudes, and also in the tropics. The most important impact is observed during the melting season which is delayed by the forest removal. This result is consistent with preliminary stand-alone experiments showing that the atmospheric boundary layer can be heated by the forest, even if the ground is covered by snow. The study confirms that vegetation feedbacks should be included when performing future climate studies such as doubled CO2 experiments, even though many uncertainties still remain with regard to other physical aspects of the climate models.