Probability plot showing the effect of different melt production regimes for Earth-like and Venus-like instellations. All model runs assume surface-dependent ingassing. Higher probabilities imply that the model is more likely to reach temperatures above 400 K. Earth-like models are in shades of blue, and Venus-like models are in shades of orange, similar to Figure 7. Dotted lines and the lightest shade indicate a constant melt production of 40 km³ yr⁻¹. Medium shades represent a constant melt production of 20 km³ yr⁻¹. The darkest shades of each color represent the decreasing melt production associated with secular cooling used in all Monte Carlo calculations presented in the main text. Higher constant melt productions require more surface water to maintain habitable surface temperatures.