Concentration of methane in the troposphere deduced from 1951 infrared solar spectra

The 1-2 percent increase in tropospheric methane determined from gas chromatographic measurements since 1977 has important implications for atmospheric photochemistry and climate. To extend the measurement baseline, solar absorption spectra have been analyzed and mean troposphere CH4 mixing ratios for the years 1951 and 1981, and an average rate of CH4 increase of 1.1 + or - 0.2 percent per year is found for this period.