"Atmospheric methane" refers to the methane gas that is present in the Earth's atmosphere. Methane is a powerful greenhouse gas that contributes to global warming. Its presence in the atmosphere can impact our climate and environment.
Direct records of atmospheric methane concentrations only go back about 800,000 years. (eos.org)
A combination of historical ice core data and air monitoring instruments reveals a consistent trend: global atmospheric methane concentrations have risen sharply in the past 2000 years. (earthobservatory.nasa.gov)
That just proves that human use of natural gas has nothing measurable to do with atmospheric methane levels. (wattsupwiththat.com)