report · Scaffold reference reports · 18 August 2026

The Mauna Loa CO₂ record as a reference dataset

How a sixty-year atmospheric series is published, versioned and cited — and what environmental-economic accounts can borrow from it

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

This report is the scaffold's long-form demonstration: a `type: report` document with a cover page, a contents page and running headers in its PDF. It re-uses the atmospheric CO₂ analysis cells built for the Mauna Loa reference analysis, but frames them the way an institutional report would — background, data and methods, results, implications — so that every part of the report template that only matters at length (section hierarchy, pagination, cross-references across pages, print furniture) is exercised against real data.

Key messages

  • Atmospheric CO₂ at Mauna Loa reached 429.12 ppm in July 2026; the 2025 annual mean of 427.35 ppm is 111.4 ppm above the first full year of the record (1959).
  • The record is a model of how a long-lived dataset should be published: stable files, explicit provenance, a documented method, and a citation request from the publisher.
  • Environmental-economic accounts that cite an atmospheric baseline should carry the same lineage — file, version, publisher — next to the number, which is what the scaffold’s data-bundle contract does.

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

Summary

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

Background

The measurement programme

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’s Global Monitoring Laboratory (Lan et al., 2026). Its longevity is the point: a measurement that has been made the same way, at the same place, for more than sixty years, with every change of instrument or procedure documented.

Why an accounting scaffold cares

For SEEA (System of Environmental-Economic Accounting)-style work the value of a series like this is not any single number but its lineage. An account that cites an atmospheric baseline needs to know which file, which version and which publisher’s citation applies (United Nations et al., 2021). This report follows the data from NOAA’s files, through a versioned bundle, to the figures below.

Data and methods

The bundle

The values on this page are read at build time from the noaa-mlo-co2 bundle described under Data: monthly means, annual means and annual growth rates, with NOAA’s flags for interpolated months carried through. Nothing in the text is typed by hand — change the bundle, rebuild, and the numbers update.

Treatment of gaps

Results

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).

The rate of increase

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.

Decadal averages make the acceleration plain (Figure 3, Table 1): about 0.86 ppm per year in the 1960s against about 2.42 ppm per year in the 2010s.1

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.

Implications for accounts

Three practices transfer directly from the NOAA record to accounting work. First, publish the file, not just the figure: a reader must be able to reach the rows a number came from. Second, version the release and say what changed — NOAA’s files carry creation dates and the bundle carries a changelog. Third, ask to be cited in a specific form, and make that form easy to copy; the citation block at the end of this report does the same for the report itself. 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). The Mauna Loa CO₂ record as a reference dataset: How a sixty-year atmospheric series is published, versioned and cited — and what environmental-economic accounts can borrow from it (v1.0). Centre for Sustainable Development Reform. https://test.csdr.global/reports/mauna-loa-reference-2026/

BibTeX
@techreport{csdr_mauna_loa_reference_2026_2026,
  title = {The Mauna Loa CO₂ record as a reference dataset: How a sixty-year atmospheric series is published, versioned and cited — and what environmental-economic accounts can borrow from it},
  author = {CSDR Platform Team},
  institution = {Centre for Sustainable Development Reform},
  year = {2026},
  version = {1.0},
  url = {https://test.csdr.global/reports/mauna-loa-reference-2026/}
}

Changelog

  • v1.0 (2026-08-18) — First release, built from the NOAA GML files dated 5 August 2026.

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