

Because humans just existing produces far less pollution than humans producing a lot of stuff.
It’s trivial to say that a bunch of hunter-gatherers don’t pollute much but we’re not generally willing to relegate people to living in the stone age.
Our economic choices have a much larger impact on pollution than our personal choices do. Ideally we’d have a measure of pollution per consumption. Everyone would have a score that calculates the total pollution created by the entire supply chain that supports their choices. So if a mine in Africa is polluting so a Chinese guy can have a nice air condition, that should be counted for China; and if a factory in China pollutes so that a guy in the US can have a new Iphone, that should be counted for the US.
I’m not aware of any such data set. The closest proxy would be GDP or GNP. That essentially provides a measure of how much pollution the total lifestyle of that population produces.
It’s a better measure but not a perfect one. The big problem with the US-China GDP comparison is that the US has much more of a service economy while China has a much more manufacturing based economy.
Manufacturing pollutes much more than services do but services don’t exist without the manufacturing.
That’s why I was saying a better measure would be pollution per GNP. That would cut out services and basically just count manufacturing output. That would make sense because it’s the biggest source of pollution and it’s the source you can do the most about (ie there’s a lot of room to make many parts of the manufacturing chain cleaner).
Nobody is as green as their marketing suggests and China is no exception. China is making huge investments in green tech and there’s still a long way to go.