This is the average amount of methane (CH4) that is in the atmosphere in a given month. The monthly average highlights the seasonal variation. The graph shows the last 3 years to highlight the seasonal variation.
Methane has a large warming effect, considering its much higher Global Warming Potential (GWP) than CO2, but it acts for a relatively brief period compared to CO2. Methane breaks down quickly in the atmosphere, and a reduction in emissions can cause a rapid decline in its levels and impact.
The primary unit here is parts per billion (ppb), which describes the average concentration of atmospheric methane per year. The secondary unit here is megatonnes, which describes the average weight of atmospheric methane per year. We show this to be able to relate to emissions, which are commonly expressed in megatonnes.Wikipedia: Parts-per notation
We see a seasonal cycle with peaks around April and November and lows around February and July. A combination of the following causes drives these seasonal differences:
The data is from NOAA’s Global Monitoring Laboratory. We are specifically using the monthly average instead of the deseasonalized trend.
Globally averaged marine surface monthly mean dataCredits: Ed Dlugokencky, NOAA/GML (gml.noaa.gov/ccgg/trends/trends_ch4/)Update cycle: monthlyDelay: ~ 3 months