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This paper describes the global height-resolved methane(CH<sub>4</sub>) retrieval scheme for the Infrared AtmosphericSounding Interferometer (IASI) on MetOp, developed at the RutherfordAppleton Laboratory (RAL). The scheme precisely fits measuredspectra in the 7.9 micron  region to allow information to beretrieved on two independent layers centred in the upper and lowertroposphere. It also uses nitrous oxide (N<sub>2</sub>O) spectralfeatures in the same spectral interval to directly retrieveeffective cloud parameters to mitigate errors in retrieved methanedue to residual cloud and other geophysical variables. The schemehas been applied to analyse IASI measurements between 2007 and2015. Results are compared to model fields from the MACC greenhousegas inversion and independent measurements from satellite (GOSAT),airborne (HIPPO) and ground (TCCON) sensors. The estimated error onmethane mixing ratio in the lower- and upper-tropospheric layersranges from 20 to 100 and from 30 to 40 ppbv, respectively, and erroron the derived column-average ranges from20 to 40 ppbv. Vertical sensitivity extends through the lowertroposphere, though it decreases near to the surface. Systematicdifferences with the other datasets are typically  < 10 ppbv regionally and  < 5 ppbv globally. In theSouthern Hemisphere, a bias of around 20 ppbv is found withrespect to MACC, which is not explained by vertical sensitivity orfound in comparison of IASI to TCCON. Comparisons to HIPPO and MACCsupport the assertion that two layers can be independently retrievedand provide confirmation that the estimated random errors on thecolumn- and layer-averaged amounts are realistic. The data have beenmade publically available via the Centre for Environmental Data Analysis (CEDA) data archive (Siddans, 2016)

Global height-resolved methane retrievals from the Infrared Atmospheric Sounding Interferometer (IASI) on MetOp