Note that China has no ability to impact global CO2 emissions either.

Let’s split China population in k Denmark-sized groups, plus one smaller-than-Denmark reminder.

None of the k groups has any ability to impact global CO2 emissions (same as Denmark).

We can reasonably assume that a smaller group has even less ability to impact global CO2 emissions than a bigger group. Hence the smaller-than-Denmark reminder has no ability to impact global CO2 emissions either.

Thus China is made of groups that have no ability to impact global CO2 emissions either. And therefore China as a whole has no ability to impact global CO2 emissions. (Otherwise at least one group within China would have to impact global emissions and we just saw that it isn’t possible).

This is known as the CO2 impossibility theorem, loosely based on Arrow’s concept of “(in)decisive” set.

Your logic is wrong - a Denmark sized group of Chinese people is probably all it takes to operate their solar panel producing factories.

The reason Denmark can't do anything isn't because there are few of them, it is because Denmark isn't a significant industrial cluster for energy technology and innovation. For example, India has more people than China and they aren't in a position to do much unless there is some sort of tech breakthrough that hasn't made it to my notice.

Certainly you are just demonstrating the opposite. Everyone has the ability to impact global CO2 emmissions.

We certainly need international coordination or actors with a minimal set of morals to achieve it.