Abstract: This data set includes records of the delta carbon-13 (δ<sup>13</sup>C) of methane (CH<sub>4</sub>) in firn air from the South Pole and trapped in bubbles in a short ice core from Siple Dome, Antarctica. Using two firn air samples, one from January 1995 and the other from January 2001, investigators reconstructed records of the isotopic composition of paleoatmospheric methane covering the last 2 centuries, from 1820 to 2001. Data are in Microsoft Excel and Microsoft Word formats and are available via FTP.