AN EMPIRICAL-ANALYSIS OF THE STRENGTH OF THE PHYTOPLANKTON-DIMETHYLSULFIDE-CLOUD-CLIMATE FEEDBACK CYCLE

The possible influence of the marine biogeochemical sulfur cycle on th e global climate has been a topic of much recent research. Based on th e hypothesis that phytoplankton could affect cloud albedo by producing dimethylsulfide, which is a precursor to aerosols and cloud condensat ion nuclei, and that cloud albedo could in turn affect the productivit y of the phytoplankton, the presence of such a feedback cycle would ha ve significant implications for models of global climate change. By co nsidering available data on the relationships between individual compo nents of the proposed feedback, an empirical model is developed of the cycle as a whole, allowing an assessment to be made of the degree to which the cycle could thermostatically regulate the climate. It is est imated that the feedback strength is about 20% (10% - 50%) of that whi ch would be necessary to completely counteract a perturbation to the g lobal climate, such as is anticipated due to accumulation of anthropog enic greenhouse gases.