Atmospheric methane is the methane present in Earths atmosphere. The concentration of atmospheric methane is increasing due to methane emissions, and is causing climate change. Methane is one of the most potent greenhouse gases. Methanes radiative forcing (RF) of climate is direct, and it is the second largest contributor to human-caused climate forcing in the historical period. Methane is a major source of water vapour in the stratosphere through oxidation; and water vapour adds about 15% to methane's radiative forcing effect. The global warming potential (GWP) for methane is about 84 in terms of its impact over a 20-year timeframe, and 28 in terms of its impact over a 100-year timeframe. 
Since the beginning of the Industrial Revolution (around 1750) the methane concentration in the atmosphere has increased by about 160%, and this increase is almost entirely caused by human activities. Since 1750 methane has contributed 3% of greenhouse gas (GHG) emissions in terms of mass but is responsible for approximately 23% of radiative or climate forcing. By 2019, global methane concentrations had risen from 722 parts per billion (ppb) in pre-industrial times to 1866 ppb. This is an increase by a factor of 2.6 and the highest value in at least 800,000 years.
Methane increases the amount of ozone (O) in the troposphere ( to  from the Earths surface) and also in the stratosphere (from the troposphere to  above the Earths surface). Both water vapour and ozone are GHGs, which in turn add to climate warming.