Since the failure to agree binding international carbon emissions targets in Copenhagen three and a half years ago, the best to be said for global climate negotiations is that they have at least kept alive – just – the aspiration to strike a deal. Any prospect of actual success, however, remains shackled by Beijing’s unwillingness to commit to legally binding emissions caps, and the refusal of important rich country polluters, above all the US, to accept limits that are not also binding on China.

Pointing the finger at China is in part self-serving – Washington has more than its fair share of isolationists and climate sceptics who do not want the US to curb its emissions in any circumstances. But blaming Beijing is justified, whatever the motives. China now pumps more CO2 into the atmosphere than any other country. A deal without Beijing will fail not only diplomatically, but also in terms of the world’s ability to bring emissions under control.

The possibility that China might drop its opposition to binding carbon caps is therefore momentous – if it materialises. That is a big “if”. The country’s economic planning policy is reportedly considering a carbon cap for its 2016-20 five-year plan. But such a policy remains at the drawing board for now. Even if it gains champions within the government, it will encounter strong resistance, in particular from interests in heavy industry. And deciding on self-imposed domestic caps is not the same as signing up to legally binding international commitments.