Yes, but people in Europe and US are among the last to be affected by Climate Change. This means they will only cooperate if you manage to not piss them off. Telling people they should not have a second child is very potent at pissing them off. If you're curious how a pissed off person looks like, see a case of Trump, a person who totally declines to cooperate with you.

This is unless you have an army to extort measures from unwilling people in the Europe and US. I think you really don't have one. So please consider how you can avoid annoying the very people who could help you.

It's more important to not lose points in the eyes of 2/3 of population (people from, or with, families of more than 1 child), than scoring points with 1% Climate Change fanatics who. A person being told their second child is a sin against planet, a Trump voter next season.

There is also a case of not understanding geometric progression. At fertility of 1.5, 80 mln germans are 60 mln in a generation and 45 mln in two generations. At fertility of 3.9, 140 mln nigerians are 270 mln in a generation and 530 mln in two generations. Who would produce more CO2, 45 mln germans or 530 mln nigerians? This without consideration that germans will move to green tec, while nigerians will prop up their consumption standards.