Keeling Curve — Atmospheric CO₂ Breathing

Keeling Curve

Time speed 6 yr/s

Year

1958

CO₂

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Since 1958

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NH phase

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How it works

Every year the atmosphere's CO₂ level "breathes": as Northern Hemisphere spring arrives, the vast boreal forests and croplands leaf out and pull carbon down through photosynthesis, so the global average dips toward a September low. Through autumn and winter, that same vegetation sheds leaves and decomposes, releasing the carbon back and driving the level up to a May high. The Northern Hemisphere dominates this seasonal swing simply because it holds far more land — and therefore far more seasonal vegetation — than the mostly-ocean Southern Hemisphere. CO₂ is well-mixed globally within about a year, which is why a single monitoring station can track the whole planet's breath.

trend(t)    = 315 + 0.85·t + 0.0126·t²   (t = years since 1958)
seasonal(t) = amp · cos(2π·(frac(t) − 0.29))
CO₂(t)      = trend(t) + seasonal(t)

Sawtooth shape — the fast seasonal dip-and-rise riding on top of the slow, steady climb is the signature of the real Keeling Curve, recorded continuously at Mauna Loa Observatory since 1958.
Long-term trend — the rise from ~315 ppm to over 420 ppm is not seasonal at all: it is the accumulating signature of fossil-fuel combustion and deforestation, faster now than in the 1960s.
Time speed — how many simulated years pass per real second; slow it down to watch a single seasonal cycle, or speed it up to see six decades of accumulation.

Real-world relevance: the Keeling Curve is one of the most important graphs in climate science — the first direct, continuous proof that human emissions were accumulating in the atmosphere rather than being fully absorbed by land and ocean.

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Absorbing (spring/summer) Releasing (autumn/winter)

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Atmospheric CO₂ (ppm)Mauna Loa-style record, 1958 → present