I don’t think any world government really believes in catastrophic global warming.  There are some governments, such as our current Liberal government, that want to prove to the world that they are Progressive and good citizens of the world.  Climate change has become the new world religion and if you want to appear Politically Correct you need to follow the rules of this new religion.  It doesn’t matter that the climate models that this is all based on have failed.  It doesn’t matter that Carbon Taxes haven’t reduced emissions by much anywhere in the world.  It doesn’t even matter that Canada has no hope of meeting its targets.  All that matters is that you are seen as playing the game.  If you play the game well you are allowed to sell your oil and participate in trade deals.  World governments don’t believe in Climate Change but they seem to all feel it is best to be seen as playing the game.  Or in the case of Russia and China, appear to be playing the game.