As comments to your first comment have already pointed out, pollution per unit of primary energy produced in power plants can vary wildly among different parts of the world. Yes, we know that China is putting up a lot of buildings. We know that China has huge amounts of air pollution. We don't know if China would be doing either of those things to the same degree if China had a freer market and more effective rule of law. That's why observers like me think that China could still stagnate at its current level of economic development, and lose the growth magic that it (undeniably) has enjoyed during most of our adult lives.