Ken Rice, an Edinburgh University academic who selectively censors dissenting comments at his pro-AGW “and Then There’s Physics” propaganda blog, has another of mine in moderation:

tallbloke says:

OK, I’ll drop that subject and deal directly with the subject of your blog post.
You state that:

“If the Earth’s atmospheric pressure is to contribute to the enhanced surface temperature, then that would mean that the atmosphere would need to continually provide energy to the surface. It could only do this through the conversion of gravitational potential energy to thermal energy. This would then require the continual contraction of the Earth’s atmosphere.”

This quote demonstrates that you’ve fundamentally misunderstood Ned Nikolov’s hypothesis. He’s not positing a raised surface T due to an ongoing gravitational collapse producing a compression, generating heat which is then lost to space.

Atmospheric pressure produces a density gradient; i.e. it forces there to be more air molecules per unit volume at lower altitude than at higher altitude. Denser air intercepts and absorbs more of the sunlight passing through it than less dense air, producing more molecular collisions and excitation. It therefore holds more kinetic energy.The more kinetic energy it holds the higher its temperature will be.

Now, a gas at a higher temperature will expand, thus reducing density, but note well that this is a much smaller secondary effect than the increase in density caused by gravitational compression. Thus the effect of the gravitational force on atmospheric mass is to create a gradient not only in pressure and density, but temperature too.

Since 70% of Earth’s surface is covered in a medium that Ray Pierrehumbert correctly points out has great difficulty in losing energy via IR, it has to lose energy via evaporation and conduction instead. However, as a triple whammy, increased pressure suppresses the rate of evaporation because it reduces wind velocities as well as increasing the BP and raising the surface temperature. The ocean has to rise in temperature to the point where it can lose energy as quickly from its 2D surface as quickly as it gains it from solar radiation in 3D. A higher surface air pressure makes that equilibrium temperature higher than it would be with a lower surface air pressure.