Final file of data selection with n=30214 entries. Revised version: 2017-06-08. The data with event label "WDC_continuous" are used here as published on the NOAA data base (hdl:10013/epic.51034.d001). They contain WDC CH4 data measured during continuous flow analysis which have already been post-processed to a spline with constant temporal resolution of 2 years, including the support from some discrete WDC data points to improve the data set, whenever larger gaps in the continuous record appeared.The data with the event label "WDC_discrete_OSU" contain WDC CH4 data which have been measured from discrete samples on the Oregon State University (OSU). The data with the event label "WDC_discrete_PSU_adjusted" contain WDC CH4 data which have been measured from discrete samples on the Pennsylvania State University (PSU), which have been adjusted by +9.9 ppb to account for interlab offsets between OSU and PSU as described in the paper.