[tkluck]

Are you making the claim that small numbers are always irrelevant? In that case it's worth reading up on the greenhouse effect. It's unfortunately very true that water vapour and CO2 have an outsize effect on the planet's heat balance.

You mix that claim with an implication about people who don't know that number off the top of their heads, but: - work on sustainability for feelgood - are independently wealthy otherwise.

I don't understand exactly what you're implying but it doesn't seem very generalizable. Society can face arbitrarily complicated threats, to counter which we can create incentives even for those who don't know the details.

How to get political agreement on the important threats and the best (effective / fair / ...) incentives is an open problem.

[moominpapa]

That wasn't my point entirely but admittedly it was a part of it. I have not heard a good reason for why a trace gas has such an effect. Bearing in mind that 0.04% is total CO2 and human produced CO2 is a tiny fraction of that - can't seem to find an agreed on percentage on that one but happy to be enlightened. The other point I was making is that when I have asked that basic question to people who are seemingly frightened of the effects of CO2 I have got massively inflated guesstimates e.g. 50%. I just think if you are going to be scared and try and scare others you should know at least that.

[tkluck]

Gotcha, I see. You're not wrong that a combination of scientific illiteracy and political orthodoxy can give terrible outcomes. So some default skepticism is quite wise.

If you want to understand the effect of the trace gases from first principles, you can read more about it under "Effective temperature of the Earth" at https://en.m.wikipedia.org/wiki/Stefan%E2%80%93Boltzmann_law . It also links to the Wikipedia page about the greenhouse effect, which you'll appreciate more after reading about the Stefan Boltzmann law first.

[moominpapa]

OK, will read, much appreciated. Just have to deal with my fence that blew down in the high winds we had in the UK yesterday - climate change no doubt (joke). Thank you.