Born in 1925: CO2 then and now

In 1925 the air held 305.20 parts per million of CO₂, an estimate from Antarctic ice cores (Bereiter et al. 2015), interpolated between the samples either side of the middle of that year.

In 2025, the latest complete year, the annual mean at Mauna Loa was 427.35 ppm: 40% more CO₂ in the air. Figures from the data files retrieved 16 October 2026.

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<a href="https://co2stats.com/co2/born-in/1925"><img src="https://co2stats.com/graphics/born-in-1925.svg" width="1200" height="630" alt="Born in 1925: 305 ppm of CO2 then (ice-core estimate), 427 ppm in 2025 (annual mean), 40% more." style="max-width:100%;height:auto"></a>
<p>Graphic: <a href="https://co2stats.com/co2/born-in/1925">CO2Stats</a>, <a href="https://creativecommons.org/licenses/by/4.0/">CC BY 4.0</a>. Source: Bereiter, B.; Eggleston, S.; Schmitt, J.; Nehrbass-Ahles, C.; Stocker, T.F.; Fischer, H.; Kipfstuhl, S.; Chappellaz, J.A. (2015-02-04): NOAA/WDS Paleoclimatology - Antarctic Ice Cores Revised 800KYr CO2 Data. NOAA National Centers for Environmental Information. https://doi.org/10.25921/n8y4-bp27. Accessed 2026-10-15. Publication: Bereiter, B. et al. (2015), Revision of the EPICA Dome C CO2 record from 800 to 600 kyr before present, Geophysical Research Letters, https://doi.org/10.1002/2014GL061957. Dr. Xin Lan, NOAA/GML (gml.noaa.gov/ccgg/trends/) and Dr. Ralph Keeling, Scripps Institution of Oceanography (scrippsco2.ucsd.edu/). Data used under their sources' terms; no endorsement implied.</p>

Sources

Antarctic Ice Cores Revised 800KYr CO2 Data (Bereiter et al. 2015 composite): age and CO2. Bereiter, B.; Eggleston, S.; Schmitt, J.; Nehrbass-Ahles, C.; Stocker, T.F.; Fischer, H.; Kipfstuhl, S.; Chappellaz, J.A. (2015-02-04): NOAA/WDS Paleoclimatology - Antarctic Ice Cores Revised 800KYr CO2 Data. NOAA National Centers for Environmental Information. https://doi.org/10.25921/n8y4-bp27. Accessed 2026-10-15. Publication: Bereiter, B. et al. (2015), Revision of the EPICA Dome C CO2 record from 800 to 600 kyr before present, Geophysical Research Letters, https://doi.org/10.1002/2014GL061957. Retrieved 15 October 2026. Terms. Trimmed from the published file.
Annual mean CO2, Mauna Loa Observatory, Hawaii. Dr. Xin Lan, NOAA/GML (gml.noaa.gov/ccgg/trends/) and Dr. Ralph Keeling, Scripps Institution of Oceanography (scrippsco2.ucsd.edu/). Retrieved 16 October 2026. Terms.

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Another year · CO₂ in the air today