Today I introduce someone. This is someone in general, not in particular. This is someone you can find a lot, especially on the internet. He (yes, it can be she, but I simplify with just "he") believes his knowledge and understanding surpasses that of the trained experts in a field. He thinks he knows better. Thinksee Nosebetter.
The one thing you can generally say about Thinksee Nosebetter when he shows up in discussions about climate is that he is at least trying to use logic. The logic is flawed, warped, incorrect, irrelevant... but the attempt gives one hope he can be taught reality and have that replace his misconceptions. He is actually exceedingly unlikely to accept being corrected, but it at least gives one hope.
Typically a Thinksee Nosebetter tosses out very simple things that on the surface may sound reasonable but that supposedly unravel an entire well-established field of science. He knows just enough to be dangerous and wrong. The phenomenon of people lacking skills or knowledge but believing they a much higher level of that skill or knowledge has been labelled the Dunning-Kruger effect, and it is quite common in the climate "debate".
The Thinksee Nosebetter appearance I want to highlight and correct involves what I saw in the comments of a Minneapolis-St. Paul Star-Tribune article discussing how public planners are looking at ideas for adaptation to a warming world. That is worthy of discussion, but here I focus just on the Thinksee Nosebetter who thought he was overturning climate science and proving it all a hoax at least partially by talking about how relatively little carbon dioxide (CO2) there is in the atmosphere.
Indeed, while the atmosphere is about 99% nitrogen and oxygen, current CO2 concentration is around 390 parts per million (ppm). In other words on average only about one molecule out of every 2500 in the atmosphere is CO2. Human activities have so far increased CO2 concentration by about 40%. So previously CO2 was about 1 in every 3500 molecules.
Granted, that may sound at first like a trivial change. But it is very wrong to assert that since the change looks like a very small amount that it cannot have a significant impact on climate as that Thinksee Nosebetter did. The first flaw is in assuming that small numbers necessarily mean insignificance, but there is also misunderstanding about how small the relevant numbers really are.
It is quite simple to point out the fallacy in dismissing small numbers. Arsenic is toxic at a level of only about 1 part per million by mass. For some reason I doubt that the Thinksee Nosebetter who dismisses a one part per 2500 concentration of CO2 would willingly ingest a comparable amount of arsenic (about an ounce). Likewise, I suppose he would not want 1 out of every 2500 cells in his body to be replaced by cancer cells. Small numbers do not necessarily mean small impact.
But the numbers when it comes to CO2 are not really that small. I mentioned that about 99% of the atmosphere is nitrogen and oxygen. About 90% of the remainder is inert argon. What this overwhelming majority of the atmosphere have in common is that unlike CO2, the molecules of nitrogen, oxygen, and argon have no role in the atmospheric greenhouse effect. It is not hard to find an explanation of the greenhouse effect online at the level you would like. Basically, only certain molecules including CO2 and methane can absorb the energy that warms the planet above what it would be without them - these are the greenhouse gases.
All of the non-greenhouse gases are irrelevant in this context. Suppose there are thousands of choices at the bottle shop (to those not from around here, that is a local term), but only a few that you actually purchase. If all the others stayed the same price, but the price on just that handful you purchase went up, then your bill will be higher. It would be wrong to say that almost all prices stayed the same so your cost must not change much. All those others are irrelevant to you, and so it is with the non-greenhouse gases and the greenhouse effect.