analysis · Scaffold reference reports · 17 August 2026

Atmospheric CO₂ at Mauna Loa

A reference analysis of the NOAA Global Monitoring Laboratory record, 1958–2026 — the scaffold's demonstration report

  • CSDR Platform TeamCentre for Sustainable Development ReformAnalysis and production
Version
1.0
Licence
CC BY 4.0

This short analysis reads the public NOAA Global Monitoring Laboratory record of atmospheric carbon dioxide at Mauna Loa Observatory directly from a versioned data bundle and renders it through the CSDR report template. It exists to exercise every part of the template — data loaders, build-time charts with data tables and downloads, numbered figures and tables, callouts, footnotes, citations, and the citable-publication metadata — against real, well-provenanced data.

Self-contained copy of Atmospheric CO₂ at Mauna Loa (version 1.0), exported 2026-08-18. The online version carries the data downloads, the PDF and any later versions.

Key messages

  • The monthly mean CO₂ mole fraction at Mauna Loa was 429.12 ppm in July 2026; the 2025 annual mean was 427.35 ppm, 111.4 ppm above the first full year of the record (1959).
  • The rate of increase has itself increased: the mean annual increment was about 0.86 ppm per year in the 1960s and about 2.42 ppm per year in the 2010s.
  • The seasonal cycle — a spring maximum and an early-autumn minimum driven by Northern-Hemisphere vegetation — rides on top of the trend and is visible in every year of the record.

Monthly mean, July 2026

429.12ppm

NOAA GML, Mauna Loa

Annual mean, 2025

427.35ppm

+111.4 ppm since 1959

Growth rate, 2025

2.23ppm/yr

± 0.11

Annual mean increase

Why this record

The Mauna Loa series is the longest continuous direct record of atmospheric CO₂, begun by Charles David Keeling in March 1958 (Keeling et al., 1976) and continued by NOAA since 1974 (Thoning et al., 1989); the current files are published by NOAA GML (Lan et al., 2026). It is the canonical example of a data product with clear provenance, a stable schema and a citation request from its publisher — exactly the kind of source a CSDR report should be able to consume without ceremony. The values on this page are read at build time from the noaa-mlo-co2 bundle described under Data, and every figure offers the data it was drawn from.

The long-term trend

Line chart of annual mean atmospheric CO₂ at Mauna Loa rising from 316 ppm in 1959 to 427 ppm in 2025, with the slope steepening over time.
View data
yearAnnual mean (ppm)
1959315.98
1960316.91
1961317.64
1962318.45
1963318.99
1964319.62
1965320.04
1966321.37
1967322.18
1968323.05
1969324.62
1970325.68
1971326.32
1972327.46
1973329.68
1974330.19
1975331.13
1976332.03
1977333.84
1978335.41
1979336.84
1980338.76
1981340.12
1982341.48
1983343.15
1984344.87
1985346.35
1986347.61
1987349.31
1988351.69
1989353.2
1990354.45
1991355.7
1992356.54
1993357.21
1994358.96
1995360.97
1996362.74
1997363.88
1998366.84
1999368.54
2000369.71
2001371.32
2002373.45
2003375.98
2004377.7
2005379.98
2006382.09
2007384.02
2008385.83
2009387.64
2010390.1
2011391.85
2012394.06
2013396.74
2014398.81
2015401.01
2016404.41
2017406.76
2018408.72
2019411.65
2020414.21
2021416.41
2022418.53
2023421.08
2024424.61
2025427.35
Figure 1.Annual mean atmospheric CO₂ at Mauna Loa Observatory, dry-air mole fraction.Source: NOAA GML (Lan, Tans & Thoning, 2026); Scripps Institution of Oceanography for 1958–1974.

Figure 1 shows the annual mean since 1959. The curve is not a straight line: the increment added each year has grown from under one part per million in the early 1960s to two-to-three parts per million in most recent years (Figure 2). Decadal averages make the acceleration plain (Figure 3, Table 1).1

Bar chart of the annual increase in atmospheric CO₂ at Mauna Loa, 1959–2025: under 1 ppm per year in the early 1960s, mostly 2–3 ppm per year since 2010, with year-to-year variability.
View data
yearAnnual increase (ppm/yr)
19590.94
19600.5
19610.96
19620.65
19630.71
19640.31
19651.06
19661.28
19670.69
19681.06
19691.35
19701
19710.8
19721.74
19731.18
19740.96
19751.09
19760.79
19772.15
19781.3
19791.83
19801.68
19811.43
19820.86
19832.36
19841.51
19851.21
19861.47
19872.06
19882.24
19891.24
19901.2
19911.05
19920.49
19931.36
19941.95
19952.01
19961.24
19971.91
19982.97
19990.92
20001.62
20011.62
20022.51
20032.26
20041.59
20052.57
20061.69
20072.31
20081.54
20092
20102.3
20111.92
20122.65
20131.99
20142.17
20152.95
20163.03
20171.9
20182.85
20192.49
20202.3
20212.35
20221.84
20233.32
20243.33
20252.23
Figure 2.Annual increase in atmospheric CO₂ at Mauna Loa (difference between successive annual means).Source: NOAA GML.
Bar chart of the mean annual CO₂ increase by decade at Mauna Loa: rising from about 0.94 ppm per year in the 1950s to about 2.42 ppm per year in the 2010s.
View data
decadeMean annual increase (ppm/yr)
1950s0.94
1960s0.86
1970s1.28
1980s1.61
1990s1.51
2000s1.97
2010s2.42
2020s2.56
Figure 3.Mean annual increase by decade. The final, partial decade is shown for completeness.Source: NOAA GML; CSDR calculation.
Table 1.The last ten annual means and their year-on-year increases.(ppm)
YearAnnual mean (ppm)Increase on previous year (ppm)
2016404.413.03
2017406.761.90
2018408.722.85
2019411.652.49
2020414.212.30
2021416.412.35
2022418.531.84
2023421.083.32
2024424.613.33
2025427.352.23

Source: NOAA GML.

The seasonal cycle

Line chart of monthly mean CO₂ for each of the last five years, 2022–2026, showing the annual cycle peaking around May and troughing around September–October, with each year's curve above the last.
View data
month2022 (ppm)2023 (ppm)2024 (ppm)2025 (ppm)2026 (ppm)
Jan418.13419.47422.8426.65428.62
Feb419.24420.31424.55427.09429.35
Mar418.76421425.38428.15430.15
Apr420.19423.3426.51429.64431.12
May420.97424.01426.9430.51432.34
Jun420.94423.68426.91429.61431.44
Jul418.85421.83425.55427.87429.12
Aug417.15419.68422.99425.48
Sep415.91418.5422.03424.37
Oct415.74418.82422.38424.87
Nov417.47420.46423.85426.46
Dec418.99421.86425.4427.49
Figure 4.Monthly mean CO₂ for each of the last five years. An interactive version is online.Source: NOAA GML.

Within each year, CO₂ at Mauna Loa peaks in May and reaches its minimum in September or October (Figure 4), as Northern-Hemisphere plants draw down carbon through the growing season and release it in autumn and winter. The amplitude is a few parts per million — small against the trend, but a useful reminder that a single month’s reading is not a year’s mean, which is why the headline figures above quote both.

What this means for accounts

For SEEA (System of Environmental-Economic Accounting)-style work the point is not the number itself but its lineage. A carbon or ecosystem account that cites an atmospheric baseline needs to know which file, which version and which publisher’s citation applies (United Nations et al., 2021). The scaffold’s bundle contract carries that lineage next to the data, and the report’s citation block carries the report’s own. Physical-science context for the trend is given by the IPCC’s Sixth Assessment Report (IPCC, 2021).

Data

References

IPCC. (2021). Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change (V. Masson-Delmotte, P. Zhai, A. Pirani, S. L. Connors, C. Péan, S. Berger, N. Caud, Y. Chen, L. Goldfarb, M. I. Gomis, M. Huang, K. Leitzell, E. Lonnoy, J. B. R. Matthews, T. K. Maycock, T. Waterfield, O. Yelekçi, R. Yu, & B. Zhou, Eds.). Cambridge University Press. https://doi.org/10.1017/9781009157896
Keeling, C. D., Bacastow, R. B., Bainbridge, A. E., Ekdahl, C. A., Guenther, P. R., Waterman, L. S., & Chin, J. F. S. (1976). Atmospheric carbon dioxide variations at Mauna Loa Observatory, Hawaii. Tellus, 28(6), 538–551. https://doi.org/10.3402/tellusa.v28i6.11322
Lan, X., Tans, P., & Thoning, K. W. (2026). Trends in globally-averaged CO2 determined from NOAA Global Monitoring Laboratory measurements. NOAA Global Monitoring Laboratory. https://doi.org/10.15138/9N0H-ZH07
Thoning, K. W., Tans, P. P., & Komhyr, W. D. (1989). Atmospheric carbon dioxide at Mauna Loa Observatory: 2. Analysis of the NOAA GMCC data, 1974–1985. Journal of Geophysical Research: Atmospheres, 94(D6), 8549–8565. https://doi.org/10.1029/JD094iD06p08549
United Nations, European Commission, FAO, IMF, OECD, & World Bank. (2021). System of Environmental-Economic Accounting—Ecosystem Accounting (SEEA EA) [Techreport]. United Nations.

Footnotes

  1. The annual increase for a year is the difference between that year’s mean and the previous year’s, as published in NOAA’s co2_gr_mlo.csv; NOAA’s uncertainty on each annual increment is about 0.1 ppm. ↩

Cite this report

CSDR Platform Team (2026). Atmospheric CO₂ at Mauna Loa: A reference analysis of the NOAA Global Monitoring Laboratory record, 1958–2026 — the scaffold's demonstration report (v1.0). Centre for Sustainable Development Reform. https://test.csdr.global/reports/atmospheric-co2-2026/

BibTeX
@techreport{csdr_atmospheric_co2_2026_2026,
  title = {Atmospheric CO₂ at Mauna Loa: A reference analysis of the NOAA Global Monitoring Laboratory record, 1958–2026 — the scaffold's demonstration report},
  author = {CSDR Platform Team},
  institution = {Centre for Sustainable Development Reform},
  year = {2026},
  version = {1.0},
  url = {https://test.csdr.global/reports/atmospheric-co2-2026/}
}

Changelog

  • v1.0 (2026-08-17) — First release, built from the NOAA GML files dated 5 August 2026.

© 2026 Centre for Sustainable Development Reform. Licensed under CC BY 4.0.