Methane is the number two greenhouse gas in the atmosphere in terms of effect (quantity x potency)
Annual Average Methane levels (parts per billion) by Year
Average Methane Levels by Year
Information obtained from the NOAA Earth System Research Laboratory
Measurements taken at Mauna Loa Hawaii. Annual numbers derived by averaging daily measurements for each year.
Starting 2015 I am excluding 1987 data from this chart as that year's records began in April
I thank Ed at NOAA for kindly keeping me informed about the latest dataset activity
Note: Missing days from the source data file are filled by propagating previous readings or averaging nearby data to obtain the average figure.
The overall data image presented here should be very close to reality.
This chart is updated once a year, after the data is posted by NOAA - usually by the end of February, sometimes in March
Zoom out 420,000 years and you get this:
This chart showing Methane, Carbon Dioxide and Temperature Variation was created by Reg Morrison and published at http://regmorrison.edublogs.org/files/2012/03/Climate-Debate4-1if6jnl.pdf
© Reg Morrison
The increase in Methane has been generally ongoing since records have been kept starting in 1987 except for a lull in the early 2000's. Current levels are unprecedented going back over 400 thousand years.
March 5, 2019: The 2018 charts are up. Methane levels increased for the 12th year in a row although the amount of increase has decreased for the third year in a row.
See data credits for the first chart for source data
While the annual CO2 equivalence of Methane emissions is currently about a quarter of CO2, the fear is as oceans continue to warm and tundras melt a feedback loop will be triggered which will cause run-away massive levels of trapped Methane to escape into the atmosphere causing huge ecological changes which could bring about mass extinctions, including our own. So far, the worrisome uptrend in Methane levels which resumed in 2007 has been linear. Rather than wait for tipping point acceleration in the trend line, increased world wide action is required at an extraordinary level to turn these graphs of CO2 and Methane levels to the down side.
According to the EPA (http://epa.gov/climatechange/ghgemissions/gases/ch4.html), the sources of Methane emissions in the United States are:
29% - Natural Gas and Petroleum Systems (e.g. leaks in pipelines, gases escaping during fracking)
25% - Enteric Fermentation (e.g. gases from digestion released by cow belching and farting)
18% - Landfills
10% - Coal Mining
9% - Manure Management
9% - Other
Sam Carana at http://arctic-news.blogspot.com looks at the global method emissions and suggest large quantities are also being emitted via nature sources, some accelerated by global warming
28.1% - Wetlands
25.9% - Ruminants, Rice growing, Landfills and Waste
17% - Fossil Fuels and Biomass Burning (includes Biofuels)
16% - Other natural sources (Geological, lakes, wildfires, termites, etc.)
13% - Hydrates and Permafrost
Special Note for the 2017 data (edited March 31, 2018 to reflect final data):
For the preliminary data bar chart for 2017, shown earlier in the year, I assumed that the extreme outlier datum for November 20, 2017 was a preliminary-data error and for that value used the average value of the day before and after when computing the year's average figure, trimming the annual figure by about 0.30. The day figure was 2006.73. Upon inquiry about this outlier, the early indication is that this datum is real, that a "really strong, fast transport from Asia, up to Alaska, then down to MLO" (Mauna Loa Observatory) brought in "strong Asian emissions combined with the effect of the N/S latitude gradient". The intensity of this event was a very rare event as there nothing else in the full daily record which comes close to this (there are a couple dozen days or so when the values have been within the 1900-1920 range, all in the past two years). In the final bar chart this value was included when figuring the annual average.
NASA provided me with an air flow trace-back diagram illustrating the origins of the air sampled many times during the day before, the day and the day after the 2006.73 reading of November 20. Very cool!!
Methane sampling air mass trace back - November 19-21, 2017
Green Star is the location of the Mauna Loa Observatory in Hawaii
Image provided by NASA (scaled and text added here)