Outline: The Keeling Curve
The skeleton this story was built from — argument, order, key numbers, and the chart plan. Committed on purpose (see issue
Outline — The Keeling Curve
The skeleton. Prose is a rendering of this; if the prose drifts from the argument here, the prose is wrong. See #10 for why this is a committed artefact.
What this story is about
The Keeling Curve — the measured rise of atmospheric CO₂. Not a story about data wrangling. The wrangling gets a short "how this was made" section at the end and nothing more.
Argument, in order
- The chart, first. Annual mean CO₂ at Mauna Loa, 1959–2025. Show it before any prose beyond a one-line caption.
- What it is. The longest continuous direct measurement of atmospheric CO₂. Started by Charles David Keeling at Mauna Loa in 1958; continued by NOAA and Scripps after his death in 2005.
- What it says.
- 316 ppm in 1959 → 427 ppm in 2025.
- Up every single year — the annual mean has never fallen.
- Getting steeper: ~0.9 ppm/yr in the 1960s, ~2.6 ppm/yr in the last decade.
- Passed 350 ppm around 1988, 400 ppm in 2015.
- The sawtooth. Zoom to monthly data: a ~6 ppm annual oscillation — CO₂ falls each northern-hemisphere summer as plants grow, rises again in winter. Keeling was first to measure this seasonal breathing. Second chart here.
- How this was made. Brief. The NOAA source is a text file with ~40 comment
lines and negative "no data" codes;
build.tsturns it into a clean typed table. One paragraph + a link to the dataset. Mention the community-dataset column-drift bug in one sentence, link out for detail. - Friction notes (keep — useful for the skill work): charting was hand-rolled SVG because the chart syntax isn't decided; that's the next decision.
Chart plan
| # | Chart | Data | Purpose |
|---|---|---|---|
| 1 | Line, annual mean, 1959–2025, with 350 & 400 ppm reference lines | co2-annual-mlo.csv | The headline. Monotonic rise, accelerating. Above the fold. |
| 2 | Line, monthly value + deseasonalized trend, 2010–present | co2-monthly-mlo.csv | Show the seasonal sawtooth riding a rising trend. |
Both rendered by make-charts.mjs (hand-rolled SVG) — fine for now; the standard
chart mechanism is a later question (#11).
Voice
Plain and factual. No "most important line in climate science", no "the planet's breathing", no "relentless". Let the numbers carry it. A "sounds like me" pass is a separate step the author runs.
