George Monbiot sheets home the blame from Copenhagen:
The British and US governments have blamed the Chinese government for the failure of the talks. It's true that the Chinese worked hard to mess them up, but Obama also put Beijing in an impossible position. He demanded concessions while offering nothing. He must have known the importance of not losing face in Chinese politics: his unilateral diplomacy amounted to a demand for self-abasement. My guess is that this was a calculated manoeuvre guaranteed to produce instransigence, whereupon China could be blamed for the outcome the US wanted.