Centre for Sustainable Development Reform · Scaffold reference reports · Report
How a sixty-year atmospheric series is published, versioned and cited — and what environmental-economic accounts can borrow from it
Summary
Summary
Section 1
1 · Background
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.
1 · Background
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.
Section 2
2 · Data and methods
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.
2 · Data and methods
Rows are loaded from the bundle’s Parquet and CSV files by build-time loaders (data/loaders); derived quantities (annual means, decadal growth, the last five seasonal cycles) are computed in one memoised analysis cell; each chart is rendered to SVG at build with a data table and CSV/SVG downloads. The PDF and the HTML export are produced from the same build.
2 · Data and methods
Measurements from Mauna Loa Observatory were suspended after the November 2022 eruption and resumed in July 2023; December 2022 – early July 2023 values come from Maunakea, about 21 miles north. Interpolated months in the NOAA files carry negative standard deviation and uncertainty flags, and are excluded from the monthly series used here.
2 · Data and methods
The rules below say what each treatment does to the series a reader sees (Table 1). They are prose, not numbers, so they are written here rather than computed; the table is kept out of the presentation deck and printed as records rather than as a grid, because each row is a paragraph.
Section 3
3 · Results · Figure 1
Source NOAA GML (Lan, Tans & Thoning, 2026); Scripps Institution of Oceanography for 1958–1974.
3 · Results
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).
3 · Results · Figure 2
Source NOAA GML.
3 · Results
Decadal averages make the acceleration plain (Figure 3, Table 2): about 0.86 ppm per year in the 1960s against about 2.42 ppm per year in the 2010s.
3 · Results · Figure 3
Source NOAA GML; CSDR calculation.
3 · Results · Table 2
| Year | Annual mean (ppm) | Increase on previous year (ppm) |
|---|---|---|
| 2016 | 404.41 | 3.03 |
| 2017 | 406.76 | 1.90 |
| 2018 | 408.72 | 2.85 |
| 2019 | 411.65 | 2.49 |
| 2020 | 414.21 | 2.30 |
| 2021 | 416.41 | 2.35 |
| 2022 | 418.53 | 1.84 |
| 2023 | 421.08 | 3.32 |
| 2024 | 424.61 | 3.33 |
| 2025 | 427.35 | 2.23 |
Source NOAA GML.
3 · Results · Figure 4
Source NOAA GML.
3 · Results
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.
3 · Results
The same five cycles as a table (Table 3): the May peak and the autumn trough are visible in every column, and reading down any month shows the trend running through the seasons. In print the table takes a landscape page of its own — six columns of tabular numbers are a comparison, not a list — with the report’s running furniture and the table’s title repeated on every page it occupies.
3 · Results · Table 3
| Month | 2022 | 2023 | 2024 | 2025 | 2026 |
|---|---|---|---|---|---|
| Jan | 418.13 | 419.47 | 422.80 | 426.65 | 428.62 |
| Feb | 419.24 | 420.31 | 424.55 | 427.09 | 429.35 |
| Mar | 418.76 | 421.00 | 425.38 | 428.15 | 430.15 |
| Apr | 420.19 | 423.30 | 426.51 | 429.64 | 431.12 |
| May | 420.97 | 424.01 | 426.90 | 430.51 | 432.34 |
| Jun | 420.94 | 423.68 | 426.91 | 429.61 | 431.44 |
| Jul | 418.85 | 421.83 | 425.55 | 427.87 | 429.12 |
| Aug | 417.15 | 419.68 | 422.99 | 425.48 | — |
| Sep | 415.91 | 418.50 | 422.03 | 424.37 | — |
| Oct | 415.74 | 418.82 | 422.38 | 424.87 | — |
| Nov | 417.47 | 420.46 | 423.85 | 426.46 | — |
| Dec | 418.99 | 421.86 | 425.40 | 427.49 | — |
Source NOAA GML.
Section 4
Three practices transfer directly from the NOAA record to accounting work.
4 · 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).
References
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/
test.csdr.global/reports/mauna-loa-reference-2026
© 2026 Centre for Sustainable Development Reform · CC BY 4.0 · Data: Atmospheric CO₂ at Mauna Loa Observatory (NOAA GML) · The report, its PDF and this deck are built from the same source.
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