This dataset for historic ambient CH4 mole fractions is an important outcome of the FP7 InGOS project (http://www.ingos-infrastructure.eu, Grant Agreement Number 284274). Data from 20 stations have been reprocessed for the period 2000-2013; in many cases involving re-integration of chromatograms and recalibrating the time series using updated assigned values for standard gases and target gases, All data have been brought to the same concentration scale (NOAA 2004). Data have been flagged for identified periods with instrumental or sampling problems. Next to added estimations for measurement uncertainty based on repeatibility of the working standards also error estimates are added that represent uncertainty due to lab internal scale consistency, monthly reproducibility, scale transfer and where available comparison with concurrent flask sampling. More documentation can be found on https://ingos-atm.lsce.ipsl.fr/doc