LONG-TERM TREND AND SEASONAL CYCLE OF ATMOSPHERIC METHANE

Ⅰ. INTRODUCTIONMethane is one of the most abundant trace gases in the earth’s atmosphere with the current concentration of 1.7 ppm. It appears to be primarily of biogenic origins, and has long been regarded as one natural component unchanging in concentration. However, the observations corroborated by our recent work have indicated that the concentration of at-