Global column-averaged methane mixing ratios from 2003 to 2009 as derived from SCIAMACHY: Trends and variability

After a decade of stable or slightly decreasing global methane concentrations, -based in situ data show that CH4 began increasing again in 2007 and that increase continued through 2009. So far, space-based retrievals sensitive to the troposphere in the time period under consideration have not been available. we report a long-term data set of column-averaged methane mixing ratios retrieved spectra of the Scanning Imaging Absorption Spectrometer for Atmospheric (SCIAMACHY) instrument onboard Envisat. The retrieval quality after2005 was severely affected by degrading detector pixels within the methane 2v3 absorption. We identified the most crucial problems in SCIAMACHY detector degradation overcame the problem by applying a strict pixel mask as well as a new dark current. Even though retrieval precision after the end of 2005 is invariably, consistent methane retrievals from 2003 through 2009 are now possible. time series in the Sahara, Australia, tropical Africa, South America, and Asia the methane increase in 2007¿2009, but we cannot yet draw a firm conclusion the origin of the increase. Tropical Africa even seems to exhibit a negative in 2006, but an impact from changes in SCIAMACHY detector degradation be excluded yet. Over Assakrem, Algeria, we observed strong similarities between measurements and ground-based data in deseasonalized time series. further show long-term SCIAMACHY xCH4 averages at high spatial resolution provide further insight into methane variations on regional scales. The Red Basin in exhibits, on average, the highest methane abundance worldwide, while other features such as the Sudd wetlands in southern Sudan can also be identified SCIAMACHY xCH4 averages.