Keeling Curve 2D — Atmospheric CO₂ Breathing (Sawtooth Model)

This 2D companion to the Keeling Curve globe keeps the same underlying model — a slow, quadratic long-term trend from 315 ppm in 1958 toward and past 420 ppm today, with a seasonal cosine riding on top of it — but reads it the way climate scientists actually publish the Mauna Loa record: as a scrolling ppm-versus-year chart rather than a rotating shell. A seasonal-amplitude slider lets you set how large the Northern Hemisphere's growing/dormant swing is, from a flatter, more ocean-dominated hemisphere near 1 ppm up to a heavily-vegetated 6 ppm, while a small breath dial and a live "trend rate of rise" readout (the derivative of the long-term curve) show how both the yearly wiggle and the underlying acceleration have changed since 1958.