ACSOE was a Natural Environment Research Council (NERC) Thematic Research Programme to investigate the chemistry of the lower atmosphere (0-12 km) over the oceans to understand the natural processes occurring in this layer and the effects of pollutants originating from the continents on them. The project was run by scientists from UK institutes and universities between 1995 and 2000, with fieldwork carried out between 1996 and 1998 over the North Atlantic from the south of Iceland to the Canary Islands. BADC holds the atmospheric data collected during the programme, while the marine data is stored in the British Oceanic Data Centre (BODC).