per capita isn't a useful metric. Imagine if you are China and your population is declining, but your GDP is still going up so your per-capita CO2 is going up. That's not fair for them.
So you look at emissions per dollar of GDP to measure how efficiently you are producing. This is why China's own CO2 commitments are expressed as Kg per GDP. This is what they are targeting to decline, it's what they set policy around, and it's how they publicly measure their own progress. So let's use their own preferred metric:
