Developed nations still have a lot of levers for meddling around with the behavior of developing nations. E.g. subsidizing clean technology, but also, sanctions and a level of political interference (which to be realistic hasn't gone very well in the past).

In the more extreme slivers of speculation, climate change might be the thing that undoes the very concept of nation state sovereignty, when the model of absolute freedom to do whatever runs into the reality that we have the technology to affect the entire earth. On the other hand this model wasn't all that old to begin with: https://en.wikipedia.org/wiki/Westphalian_sovereignty