More than the carbon cycle
The interactions between forest ecosystems and climate comprise the biophysical effects such as the energy balance, the water cycle and the physical interactions between the forest cover and the atmosphere (the surface roughness).
The forest vegetation influences the albedo of the forest (the share of radiation reflected by the forest). Forests have a low albedo meaning that they absorb radiation. The extensive and continuous coniferous forest cover in northern Europe lowers the albedo and has a warming effect.
The evapotranspiration from the forest vegetation has a cooling effect. In the growing season of forests, it is higher for broadleaved than coniferous forests.
Impacts of forest cover on climate
Forests also emit biogenic volatile organic compounds (BVOCs). These are rapidly oxidised in the atmosphere to produce the pollutant O3.
Secondary organic aerosols may lead to cloud formation, reflect the radiation, and lead to cooling. Stress factors can cause a higher emission of BVOCs by trees.
Nevertheless, the net outcome of these biophysical processes is highly uncertain and depends on the season, cloudiness, and forest management. The significant uncertainty is why these processes are not reported nor accounted for.