“There is no controversy that there is a natural greenhouse effect, because otherwise the Earth would be a frozen snowball at this radius from the Sun.”
Of course not. Without the greenhouse effect, the earth would be -18 C (by one estimate), too cold for life to evolve. Don’t oversimplify my assertions here. The crux of this debate is whether man-made CO2 is causing the sea-level to rise, polar bears to die, and all kinds of other problems. There is ample evidence that CO2 *cannot* cause the kind of temperature changes that are claimed by IPCC.
“Consider that the surface temperature of Venus is hotter than that of Mercury despite the fact that it’s farther away and hence the solar flux is lower.”
Venus’ surface is hot due to atmospheric pressure (rather than greenhouse effect, which was once supposed). The Earth is the same way: something like 1 deg C for every 100 m? You can’t argue any clean relationship between AU distance and temperature without taking the composition of atmospheres in account.
