Greenhouse Gas Effect Cross-Section (2D)

Atmosphere Composition

CO₂ concentration 420 ppm

Radiative Balance

Radiative forcing ΔF

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Equilibrium warming ΔT

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Surface temperature

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IR trapped

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IR escaped to space

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How it works

Visible sunlight passes almost freely through the atmosphere and warms the ground. The ground re-radiates that energy as infrared heat — a longer wavelength that CO₂, methane and water-vapour molecules absorb and re-emit in random directions, sending roughly half of it back down to reheat the surface instead of letting it escape to space.

The radiative forcing from a CO₂ change follows the standard logarithmic relationship used in climate science (Myhre et al. 1998):

ΔF = 5.35 · ln(C / C₀)  [W/m²]
C₀ = 280 ppm (pre-industrial baseline)
ΔT = λ · ΔF, with climate sensitivity λ ≈ 0.8 K/(W/m²)

This is why forcing is logarithmic, not linear: each doubling of CO₂ (280→560→1120 ppm…) adds roughly the same ~3.7 W/m² of forcing and ~3 °C of equilibrium warming, regardless of the starting concentration — the first few hundred ppm already absorb most of the infrared band CO₂ can reach, so extra molecules have diminishing (but never zero) effect.

CO₂ slider — sets atmospheric concentration in parts per million; the dot density in the gas band above the ground scales with it.
Radiative forcing ΔF — the extra energy (W/m²) trapped compared to the pre-industrial baseline.
Equilibrium warming ΔT — the steady-state surface temperature rise implied by that forcing.

Sunlight (visible) Infrared — trapped Infrared — escaped