Determining tropospheric concentrations of trace gases from space

It is now possible to determine the concentrations of atmospheric constituents in the troposphere from satellite data, a development that heralds a new era in tropospheric chemistry Some of the methods for retrieving tropospheric trace gases are described here, together with some of the latest results obtained from ESA Earth Observation (EO) measurements. The likely consequences for environmental monitoring and policy are outlined, as is the new Troposat project, the aim of which is to exploit these results, together with the requirements for future instrumentation, to build on the present situation.