CO2 is NOT the only metric being captured by global agencies, it's just what was said in the comment above and is usually the target to showcase how responsible the use is basically. I am not saying that the metric in itself is bad but it is easy to mislead. China is not trustworthy when it comes to capturing data like this because their companies are basically required to make greater China look good. This is a separate beast.
If you look into how a body like the EPA calculates their emissions they reference the greenhouse protocol. In an ideal world, all use and all waste goes through a method like this protocol and individuals calculate their emissions. Governing bodies and academics alike would be using software to track each ounce of output based on raw materials. If you purchased or created a good, you should be able to track and show end of life for each individual component. This is just not the case. People don't know what is in the stuff they buy. There is a flurry of life cycle analyses cradle to gate or gate to gate or cradle to grave being produced currently to bridge this gap but it currently is not the standard for identifying output.
How does a company like Walmart track all of the emissions produced (by their farmers, their logistics, the raw material manufacturing, etc.) if it's difficult? The answer is they give ballpark numbers based on how much was purchased. Companies now have decided to use a number that was calculated based on various spends and convert that to output.
How does a country like the US measure then? In the US there are regulatory bodies that check if what we say is true but it's a complete joke. There waaaaaayyy too much data for these bodies to go through so they usually report whatever the company reports.
Circling back to China and why I say not to trust the CO2 calculations is that these companies are not trustworthy. I'll be honest I don't know if there are similar regulatory bodies in China for emissions but I doubt it. It's what allows companies to do illegal dumping into rivers and let's many claim net zero. I'm assuming based on the time you responded to me that you are in China so maybe you can elucidate me on how I get this wrong.