"The USA has emitted the most to date: around a quarter of all historical CO2: twice that of China which is the second largest contributor. "

https://ourworldindata.org/co2-emissions#:~:text=The%20USA%20has%20emitted%20the,of%20all%20emissions%20since%201750.

"Of course, this leads to much lower greenhouse gas emissions as well. Burning coal is responsible for 70% to 75% of China’s greenhouse gas emissions. Right now China’s coal emissions are in the range of 9.4 billion tons of carbon dioxide annually. Assuming this trajectory is close — and I’ll restate what I always say, that I don’t claim to be right, just less wrong than most — they’ll be roughly 3.5 billion tons in 2040. The rest of their economy will have continued to decarbonize at the current accelerated rate, so their total emissions will likely be in the range of 4 billion tons of carbon dioxide. This is nothing to write home about, still a very large number, but the trajectory indicates that very low greenhouse gas emissions by China are likely in 2050."

https://cleantechnica.com/2024/09/30/china-likely-to-have-lower-ghg-emissions-than-usa-by-2035/