Originally Posted by wogoga
It doesn't matter
if it heated the surface from a lower temperature or just keeps it from cooling down further: the sun still provides the surface with heat. If the sun stopped shining, the surface would cool, and if the surface was magically made cooler, it would heat up.
it would. A 0°C surface temperature would drastically reduce both radiative and
convective heat loss, but it would still receive the same amount of incoming heat. So there would no longer be any balance between heat in and heat out, and net heat flow in = rising temperature. Your million-year lifespan for a frozen surface is an absurdity.
completely mistaken in your thermodynamic evaluation. And what you haven't figured out is that the reasons you're wrong have nothing to do with Sagan being right, or with runaway greenhouse effects. You have made claims which don't withstand basic scrutiny.
That's correct. But that tiny heat flow comes from the fact that the surface receives some heating from solar radiation. Thermal conduction from below the surface is pretty much irrelevant. The crust itself is a FAR better insulator than the atmosphere ever could be.