Do the voters matter?
A third of CO₂ emissions come from a country that is not a democracy.
A third of CO₂ emissions come from a country that is not a democracy.
That will not work because it means people just move high emitting activities to those countries.
For example the evisceration of the British steel industry means we import steel from China: dirtier energy mix, plus transport of a very heavy commodity.
You are right that they don't have a democracy because the people are unable to truly organize without the powers that be at the top putting an end to any movements, but the people in the remaining 2/3s of the world never bother to take time to organize either, so the democracy they do have is really only a belief, something theoretical, and they if they ever decided to exercise it in the future may find out that they weren't actually under democracy after all.
If you want to compare democracies to non-democracies then you have to add all the other non-democracies too which would give you more than half.