Anthropogenic and natural perturbations of the carbon cycle

A summary is given of recent results and unsolved problems regarding the carbon cycle. There is a lack of knowledge concerning the amounts of CO2 released by deforestation and land use, the response of terrestrial vegetation to increasing CO2, gas exchange air-sea and the water exchange between surface and deep ocean. Analyses of polar ice cores have demonstrated that atmospheric CO2 was lower during glacial than during interglacial times. These natural variations must be due to a change in operation of the oceans, but the precise mechanism is not yet known. Specific recommendations for experimental and modelling research regarding the global carbon cycle are given