and the earth could retain more or less of that output,
And what causes the Earth to 'retain' heat or 'lose' it?
Plug in an electric blanket. That's the sun. It radiates heat.
Now, lie on top of the electric blanket. You are the Earth. By lying in close proximity to the heat source, you become comfortable. You like your temperature.
Now, put a big down comforter on top of your body. This (the Left would say) represents Greenhouse gases. Suddenly, your temperature is increasing as more heat is retained. If you were comfortable 5 minutes ago, now you are uncomfortably warm.
The whole question is: Can humans put a blanket on the Earth? Do we produce CO2 is sufficient quantities so as to significantly cause the planet to retain heat better and therefore raise our base temperature a few degrees?
That's the whole question of AGW. And I still don't see where the Second Law of Thermodynamics fits in.
“And what causes the Earth to ‘retain’ heat or ‘lose’ it? “
Beats me. But is there a theoretical reason why NOTHING could cause the earth to retain more heat? And if there is, what does that have to do with the Second Law of Thermodynamics?
I am not a believer in global warming. I think the idea that we knew what the average earth temperature was in 1867 to within a couple of degrees is ridiculous. The idea that we know the average temperature of the earth with precision in 29,846 BC is even more ludicrous. But I do not see how the laws of thermodynamics affect the situation...