There’s been a rather lengthy Twitter thread about the greenhouse effect. In particular, focusing on claims that there is no such thing. Of course, engaging in such discussions so as to actually change anyone’s minds is pointless. However, I think there is still merit in pointing out the errors in what some are suggesting (if only for the benefit of some onlookers) and it can be moderately enjoyable (in the sense that you’re forced to think about how to present your arguments, and that can be challenging).
There are, however, a couple of things that I found quite remarkable. One is how comfortable some are in being compared to great scientists of the past who have been instrumental in over-throwing paradigms. They certainly don’t let humility get in the way of progress. The other is how quickly it becomes clear that they’re really arguing against a simplistic caricature of the greenhouse effect. I’ve certainly encountered this on a number of occasions before.
There are many ways to explain the greenhouse effect, but in a simple sense it is simply that the atmosphere is mostly transparent to incoming solar radiation, while being opaque to the outgoing longwavelength radiation coming from the surface. This causes the surface to be warmer than it would otherwise be.
There are a number of basic consequences of the greenhouse effect. One, for example, is that thespectrum we would observe from space has various features associated with the absorption of outgoing radiation. Also, we would expect to see downwelling longwavelength flux at the surface.
What’s remarkable is that these all seem to be things that those who dispute the greenhouse effect accept. However, they don’t seem to regard these as indications of a greenhouse effect. The problem, though, is that if there is no atmospheric greenhouse effect, then the atmosphere should be radiatively inactive and we should not observe any atmospheric absorption in the outgoing spectrum, or any downwelling longwavelength flux. Accepting these observations, while disputing the greenhouse effect, is therefore rather inconsistent.
So, it seems that at least some who dispute the greenhouse effect accept most of the observations that would be regarded as confirming it. I would like to think that this is simply because they’re confused, but I suspect it is strongly influenced by what accepting the greenhouse effect would imply.