These statements have been made before, however the Chinese president has reaffirmed them over video-link to the UN general assembly. Currently responsible for around 28% of world emissions this is highly encouraging.
In the past China has agreed to its peak emissions point, but not to its carbon neutral point.
It has to be said that this may be a case of high politics, as the speech followed Donald Trump who has injected much hesitancy into the conversation. Joe Biden the new president has already made many positive moves, mainly by undoing the moves made by the previous administration.
Might this be the start of a fight between the two biggest economies (they are also the worlds biggest carbon emitters) as to who is going to lead the fight against climate change? While it would be a funny thing to see them competing on, it may well accelerate both towards cutting their emissions faster. Given that the 2 countries have combined emissions of 43% of the worlds emissions this can only be good.
A race to net zero emissions would be fantastic for the world, as a world our emissions must fall by 60% by 2050, a race between these two countries could see us get 2/3 of the way there without the efforts from everyone else.