The FTIR-spectrometry has been established as a powerful tool to study the composition of the atmosphere remotely. Using the sun as light source, the analysis of ground-based absorption spectra allows retrieving the concentrations of up to 20 atmospheric trace gases. Analysing the line shape of isolated spectral lines allows retrieving the vertical concentrations of about 10 different trace gases. We perform such observations at several stations in the Arctic, at midlatitudes, and in the tropics.

Greenhouse gases have been studied using in situ measurements since more than 50 years, but remote sensing of measurements only became available within the last couple of years. The remote sensing measurements measure the total column, which is a different quantity than measured by the in-situ measurements. It is expected that column measurements will become abundant and largely independent constraints on carbon cycle processes. The remote sensing measurements will help to improve the currently inadequate understanding of the location, nature and magnitude of the sources and sinks of greenhouse gases. A better characterisation of the sources and sinks of greenhouse gases is currently the most important topic in atmospheric research. An important constraint on the sources and sinks is the observed latitudinal gradient in atmospheric greenhouse gas concentrations.