China's not a member of Answerbank, though, at least as far as I'm aware.
Also, while the point you are making is technically correct -- I of course accept that the UK alone can do little or nothing about this -- it's also a question of leadership. The most recent moves from the US to generally step backwards, for example, need to be combatted and resisted, but it would be harder to do that if we were not also trying ourselves to tackle the problem.
The criticism of China is also an interesting point. Absent leadership from the US recently, it's actually China that has stepped up to become the main driver of the Paris Treaty, and frankly that's a travesty. They are, to be sure, some of the biggest investors in various renewable energy sources, but that's for cynical reasons. In that sense, then, the lack of leadership shown by the US, and with only a limited role the UK can play, has left a nasty vacuum at the top that deserves to be tackled.
The main problem is that everyone seems happy enough to blame everybody else. As long as that continues, nobody will actually tackle anything, and the risk posed by climate change will then only continue to grow.