At the Izaña Atmospheric Research Center, high-resolution mid-infrared solar absorption spectra have been recorded for more than 12 yr using Fourier Transform InfraRed (FTIR) spectrometers. We use the spectral fitting algorithm PROFFIT to retrieve long-term time series of methane (CH<sub>4</sub>) from the measured spectra. We investigate the total column-averaged dry air mole fractions of methane (totXCH<sub>4</sub>) obtained from a profile scaling and a profile retrieval, and apply two approaches for deriving the tropospheric column-averaged dry air mole fractions: firstly, we use the FTIR hydrogen fluoride (HF) total column amounts as an estimator for the stratospheric CH<sub>4</sub> contribution and a posteriori correct the totXCH<sub>4</sub> data of a profile scaling retrieval accordingly (troXCH<sub>4<sub>post</sub></sub>); secondly, we directly determine the tropospheric column-averaged dry air mole fractions of methane (troXCH<sub>4<sub>retr</sub></sub>) from retrieved CH<sub>4</sub> profiles. Our theoretical estimation indicates that the scaling retrieval leads to totXCH<sub>4</sub> amounts that are subject to a large smoothing error, which can be widely avoided by applying a profile retrieval (for the latter we estimate an overall precision of 0.41%). <br><br> We compare the different FTIR CH<sub>4</sub> data to Izaña's Global Atmospheric Watch (GAW) surface in-situ CH<sub>4</sub> data (CH<sub>4<sub>GAW</sub></sub>), which in the case of the Izaña Atmospheric Research Center high mountain observatory are very representative for the free tropospheric CH<sub>4</sub> amounts. Concerning totXCH<sub>4</sub>, the agreement between the FTIR data product and the in-situ measurement is rather poor documenting that totXCH<sub>4</sub> is not a valid free tropospheric CH<sub>4</sub> proxy, as it is significantly affected by the varying stratospheric CH<sub>4</sub> contribution and it rather follows the variation in the tropopause altitude. The a posteriori correction method as applied here only removes a part of this stratospheric CH<sub>4</sub> contribution. In contrast the profile retrieval allows for a direct estimation of the tropospheric column-averaged CH<sub>4</sub> amounts. Results of the profile retrieval analysis correlate well with the CH<sub>4<sub>GAW</sub></sub> data (correlation coefficient of 0.60, FTIR-GAW scatter of 0.97%), and both data sets show very similar annual cycles and trend behaviour for the 2001–2010 time period. Furthermore, we find a very good absolute agreement between the troXCH<sub>4<sub>retr</sub></sub> and CH<sub>4<sub>GAW</sub></sub> (mid-infrared FTIR/GAW scaling factor of 0.9987) suggesting that mid-infrared FTIR data can be well combined with the surface in-situ GAW data. <br><br> Our study strongly supports the value of mid-infrared ground-based FTIR CH<sub>4</sub> profile retrievals as well as the robustness of the approach for achieving total and tropospheric column-averaged XCH<sub>4</sub> data of high quality.