Abstract
The concentration of methane has been measured in tropospheric air samples collected in remote locations between 55°N and 53°S during six collection periods between November 1977 and November 1980. The observed concentrations of CH4 have increased in each of six latitude locations by an average of 0.052±0.005 ppmv between January 1978 and January 1980.This (1.4±0.2)×1014 gram increase in the total atmospheric burden of CH4 corresponds to 35±12% of the yearly flux of (4.0±1.3)×1014 grams needed to maintain the CH4 concentration in steady‐state at its recent level of about 1.6 ppmv. The 1978‐1980 excess of about 0.7×1014 grams per year of sources over sinks for CH4 could arise from either an increase in biogenic releases or from a decrease in the average OH radical concentration in the lower troposphere, or from both.
Highlights
The presenceof CH4 in the atmospherewas established more than 30 years ago by infrared spectroscopy{Migeotte, 1948} and its concentration was measured sporadieally over the 20 years {Junge, 1963; Ehhalt, 1974; Dianov-Klokov et al, 1975}
Thesemeasurementsprior to 1970 demonstrated that CH4 concentrations showedsome variability with geographic location, but generally had neither frequency nor precision sufficient to permit conclusions concerning the existence of trends with latitude, season or year
Evidencheas appeared that the concentrations of CH4 in particular locations have varied with season and increased with time, and has led to suggestions that the increase is a general worldwide phenomenon{RasmusseanndKhalil, 1981a,b; Fraser e__t al., 1981;Rowlanedt al., 1981}
Summary
The presenceof CH4 in the atmospherewas established more than 30 years ago by infrared spectroscopy{Migeotte, 1948} and its concentration was measured sporadieally over the 20 years {Junge, 1963; Ehhalt, 1974; Dianov-Klokov et al, 1975}. Thesemeasurementsprior to 1970 demonstrated that CH4 concentrations showedsome variability with geographic location, but generally had neither frequency nor precision sufficient to permit conclusions concerning the existence of trends with latitude, season or year. The precision of the successive measurements from any particular sample wasi0.005 ppmv,while the absolute reproducibility of the comparisonstandardis 0.010 ppmv over a period of more than two years. Repetitive measurements of a series of aliquots from the same sample made over a three-year period have shown no change relative to the comparison standard beyond these limits. Our data taken at seven different latitudes for six collection periods are given in Tables 1 and 2 and Figure 1. At each of these seven latitudes the CH4 levels increasedfrom 1978to 1979to.
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