The abundance of CH4 in the earth’s atmosphere was determined by assuming an effective temperature for the atmosphere of 250°K. The linesR(0) and P(2) of the 2v3 band were used since they are sensibly single and are easily broadened so that the total integrated intensity can be determined. The result of 1.11±0.16 cm.atm (NTP) is in good agreement with previously published results obtained by using less realistic effective temperatures.
UWE FINK, D. H. RANK, and AND T. A. WIGGINS, "Abundance of Methane in the Earth’s Atmosphere," J. Opt. Soc. Am. 54, 472-473 (1964)