"in what age has what China said or promised been reliable". All due respect. The Chinese government, for good or bad, has been pretty consistent in its foreign policy and promises. Certainly much more than the current US administration. Sadly, if I had to trust one vs the other at their word it would be China.

I suspect China's adoption of the Paris accord has more to do with domestic concerns than international. Chinese measure weather by the number of "blue sky" days (with limited pollution). Besides they have the world's large green energy industry adoption of green energy will be good for business.