China has 3 times the population of the US, yet just passed the US in overall pollution, meaning that if they get up to the US' technological level, they'll pump out 3 times more pollution, even without a population increase. Why is there too much pollution in the world? Over-population. Less people=less pollution. Even you can grasp that simple concept.
Oh brother...
You seem to assume that clean technology will not continue to improve the way that all other technology has over time...
You also don't seem to understand that China's industrial output is at present dedicated mostly to exports. If China's population were cut in half overnight their need for industrial production would not be.
China faces some unique challenges relating to its population, but within the next several decades those will shift decidedly toward the problem of having too rapidly shrinking a populace, with all the attendant issues that brings (and which almost all nations will 'soon' face).
All in all, you're just an idiot.