It’s true that we’ve stopped some especially bad things - the anti-CFC campaign should get more attention – but part of the problem is that we haven’t improved in aggregate. If Californians drive cars which get 50+ mpg with low emissions, but a hundred million people in India start driving new cars with less strict emissions controls, the planet is in aggregate worse off. Something over half of the CO2 in the atmosphere was emitted after 1990, which is a general proxy for the rest of the world industrializing.