He would like to convince you that because the sun gives out broader bands of IR than the ones that CO2 accepts, somehow CO2 does not cause warming.

But all this about IR from the sun is waay beside the point. The energy we receive from the sun is overwhelmingly in the visible spectrum. This part does the lion’s share of the heating. It’s also part of the reason greenhouse gases matter so much. They don’t much filter the incoming radiation, because most of it is at wavelengths to which those gases are transparent. So the energy from the sun gets in without too much loss. [Yes, clouds do reflect a lot.] It’s when the heated daytime surface reradiates to the sky that the greenhouse effect really kicks in.

Imagine you’re in a boat, bailing. But of every bucket you throw overboard, a substantial fraction splashes right back in. Your boat will be wetter than if you didn’t have that splashback. In the same way, the earth cools off slower at night than if it didn’t have CO2 in the atmosphere. And so what if the splashback isn’t 100 percent. Something is still more than nothing.

Common experience can be instructive. The nights grow cool faster in the desert. Why? Because there’s little water vapor between the ground and space. Water vapor is a potent greenhouse gas, and guess what? Humid nights stay hot, arid nights cool faster.

A less common folk observation, but one that millions can testify to, is that at high altitudes, the nights grow cool faster. Fifty degree temperature swing territory once you get to 5000 meters or so. Why? Because when you’re high enough that half the atmosphere is below you, half the CO2 and more than half the water vapor is below you. Less CO2, less greenhouse effect, and sure enough, the heat escapes faster. Less “splashback.”

Here’s one point on which I had to educate myself. There’s enough CO2 in the atmosphere to utterly block transmission of a beam of IR light at a frequency in its absorption frequency. So how does anything get out? It’s a matter of layers. The top layer, the one above which there’s too little CO2 to capture much of anything, is at some temperature or other and it radiates some amount or other. How much it radiates depends on how much it gets from the next lower layer. And so on. The thing becomes a calculus problem. A 19th century physicist named Tyndall worked out the details.