Han wrote:

And another issue is that somebody has to figure out how to do
something about China. Even if the entire rest of the world stops
producing CO2 at all, the Chinese will still be producing nearly as
much as the rest of the world combined was when China signed Kyoto.

I fully agree. But should that absolve us of the responsibility to do
what we reasonably can do??

Yes. It's called "futility."

Your efforts could be put to better use than being part of the bucket
brigade trying to bail the Titanic.