>Here's what I think the flaw is: the more a planet heats up, the more it can radiate into space as infrared radiation. What do you mean by that? The planet ra

>Here's what I think the flaw is: the more a planet heats up, the more it can radiate into space as infrared radiation. What do you mean by that? The planet radiates exactly as much heat out as it absorbs from incoming starlight. The only thing that change this parameter is the planet's albedo. Darker planets radiate away more heat because they absorb more heat. Even radiant forcing (from CO2 et al) doesn't change the equilibrium amount of infrared radiation escaping, just the surface temperature required to achieve radiant balance. Note that increasing the surface temperature reduces the amount of thermodynamically useful energy (exergy) available to the biosphere, because it's like increasing the heatsink temperature of a Carnot engine.