Different climate regimes as a function of time and planetary distance a. Planets in the white region are globally glaciated, those in the green area are ice free and habitable, and those in the orange region are undergoing a runaway greenhouse. Both glaciated and ice-free equilibrium states exist in the cyan region, and neither equilibrium exists in the gray area. The brown region contains planets that have habitable temperatures but CO₂ pressures <10⁻⁵ bar. Model parameters are W_L0 = W_S0 = 1/6, β_L = β_S = 0.3, and θ_L = θ_S = 10 K.