427.21
CO₂ at Mauna Loa (ppm)
CO₂ → Temperature Impact
Interactive real-time comparison of three major climate sensitivity models
Classic IPCC
(Myhre 1998 → AR5)
ΔF = 5.35 × ln(C/C₀) → 3.0 K per doubling
CO₂: 635 ppm | Forcing: 0.00 W/m²
ΔT = +0.00 K
ECS ≈ 3.0 K (IPCC best estimate)
CMIP6 Models
(2020–present)
Ensemble mean → ~3.9 K per doubling
CO₂: 635 ppm | ERF: 0.00 W/m²
ΔT = +0.00 K
CMIP6 mean ECS ≈ 3.9 K
Happer–van Wijngaarden
(2020–2023)
HITRAN, no WV feedback → 1.4–1.5 K per doubling
CO₂: 635 ppm | Forcing: 0.00 W/m²
ΔT = +0.00 K
Planck only (~2.2 K with WV feedback)