There are so many errors and misstatements in Larry V. Ridlen Jr.’s letter that one hardly knows where to start. But in the first place, CO2 is a tri-atomic molecule, and it absorbs infrared radiation from the Earth’s surface by vibrating and rotating. This means that rather than being transparent, as it is to sunlight, the atmosphere absorbs infrared radiation from the Earth’s surface, primarily because of atmospheric CO2 but also other gases such as methane, thus, in some sense, “trapping” it. In short, everything in Ridlen’s first two paragraphs is dead wrong.

On the matter of condensation of CO2, this happens when thermal energy is extracted from the gaseous state, say, so that solid CO2, or dry ice, can be formed. Heat it up, and dry ice becomes gaseous CO2, but in this case, most of the energy goes into thermal motion of the molecules, while some goes into rotations and vibrations, depending on the frequencies involved.

With regard to Venus, it receives nearly twice as much solar energy as the Earth, not 243 times! And its CO2 atmosphere, 100 times as dense as Earth’s, traps the infrared radiation from the surface, resulting a “runaway greenhouse effect.” The trapped heat eventually heats Venus’ atmosphere until it radiates into space as much energy as it receives from the sun. Venus is, indeed, a good model for what it happening on Earth, if an extreme one.

The idea that my attic heats up as a result of direct infrared radiation from the sun is completely wrong. Visible light from the sun heats the roof structure to some 100 degrees or so, which results in it radiating infrared energy into the attic.

As for the arctic, of course, it is still cold, but the point is that it is not as cold as it once was, and this additional heat has disturbed the ice-ocean-atmosphere equilibrium. What is worse, less polar ice means less reflected sunlight and more absorbed radiation, hence more warming. This is an example of a “positive feedback” mechanism.

Finally, on clear nights, the Earth does radiate energy into the atmosphere but only colloquially “into space.” That energy is mostly absorbed (trapped) by the upper atmosphere and reradiated down to the surface.

It may be uncharitable to point out that everything in the letter is wrong, but I encourage Mr. Ridlen to do a better job of trying to understand the science behind climate change, which might, in the end, change his own mind.

Dan Purrington

physicist

New Orleans