A GEOPHYSIOLOGISTS THOUGHTS ON THE NATURAL SULFUR CYCLE

The climate depends on the atmospheric abundance of sulphur aerosols a t all levels up to the stratopause. Volcanoes, combustion and biologic al emissions all contribute and usually result in cooling. The history of this topic is lively and goes back at least to the eighteenth cent ury with Benjamin Franklin's comments on the cooling effects of the su lphuric acid aerosol from the Icelandic volcano, Laki. Mitchell first drew attention to the potential cooling effects of combustion aerosols . Charlson and his colleagues proposed that emissions of dimethyl sulp hide (DMS) from ocean algae might also be important. More recently, Lo velock & Kump drew attention to the decline of biological sulphur emis sions with global warming and the possible consequence of a positive f eedback on climate change. The geophysiological aspects, which arose f rom the Gaia hypothesis in the early 1970s, form an important part of the account that follows.