But even though the mood was optimistic and the words were full of purpose, the attention of the 40,000 assembled officials and media drifted a bit when each leader got down to the details of exactly what their country was actually doing – even at the beginning when there were still plenty of them watching.

And that’s the danger.

The pledges made so far will still result in global warming of at least 2.7 degrees, even if they are all met – much better than the 5C rise we might expect without action but still short of the 2C goal. Experience suggests there is a very big “if”, and negotiators have virtually given up on the idea that the pledges should be legally binding. Shirkers will face no real sanction, other than international opprobrium. And that means a system to check and report what each country does is critical.



But the rules for monitoring remain unfinished. The plans to regularly review and “ratchet” up the pledges to contain global warming to 2C or lower are not finalised either and will be critical. Developing countries argue they still need more finance.

Those details matter.