Atmospheric Carbon Dioxide (CO₂) and Methane (CH₄) levels, 1800–present

All CO₂ and CH₄ values are annual averages, except that 2025 values are preliminary projected estimates, based on partial-year data.

To see precise values, hover your mouse cursor over the red and blue graph traces. (However, all values are shown with about one more significant digit than is warranted by the precision of the measurements, and the ice core values are less accurate than the Mauna Loa measurements.)

Click here for a downloadable, bookmarkable image (or take a screenshot with PrtScn or the Windows Snipping Tool).

Note: We also have individual graphs of carbon dioxide (CO₂) and methane (CH₄) levels.

The relative scaling of the CO₂ and CH₄ axes was chosen so that the relative visual magnitude of changes in the two traces would very roughly approximate the relative warming effect of changes in the levels of the two gases. A 0.1 ppmv increase in atmospheric CH₄ level has 40× to 50× as much warming effect (radiative forcing) as a 0.1 ppmv increase in atmospheric CO₂ level. We used 50:1 so that the grid lines would line up nicely in the graph. ↑

(Aside: in the literature you'll often see CH₄ and CO₂ compared by so-called “global warming potential” [GWP], which is an attempt to combine the effects of both the radiative forcing and lifetimes. That is irrelevant to this graph, which depicts atmospheric concentrations, not emissions. The effective atmospheric lifetime [“adjustment time”] of CH₄ is only about 10-12 years, compared to about fifty years for CO₂. So, while the immediate warming effect of added CH4 is 40× to 50× greater than the same amount of added CO₂, the warming effect of added CH₄ diminishes much more quickly over subsequent years. Here are some references to [mostly unrealistic!] GWP estimates and discussions: [1a&b],[2],[3],[4],[5],[6].)

Sources:

1958-present CO₂ data is from https://gml.noaa.gov/webdata/ccgg/trends/co2/co2_annmean_mlo.txt. For monthly data see https://gml.noaa.gov/webdata/ccgg/trends/co2/co2_mm_mlo.txt (measurements at Mauna Loa Observatory, HI).
1850-1958 CO₂ data is from http://data.giss.nasa.gov/modelforce/ghgases/Fig1A.ext.txt (ice cores).
1800-1850 CO₂ data is from https://www1.ncdc.noaa.gov/pub/data/paleo/icecore/antarctica/law/law_co2.txt (Law Dome ice cores, 75 year smoothed).
1984-present CH₄ data is from https://gml.noaa.gov/webdata/ccgg/trends/ch4/ch4_annmean_gl.txt except that the 2024 figure is preliminary, projected from NOAA's July seasonally-adjusted monthly Mauna Loa measurements.
1800-1992 CH₄ data is from https://cdiac.ess-dive.lbl.gov/ftp/trends/atm_meth/EthCH498B.txt (ice cores), interpolated.

 

 

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Last modified: 23-Dec-2025 (version 65)