Last week, Barack Obama sent out a clear message to the US and the world when he nixed the Keystone XL pipeline which would have opened up Canadian tar sands to international markets. I’ve long argued that the litmus test of a true sustainability leader is not so much what they start doing, but what they stop doing. in this instance at least, Obama has passed the test.

And what a timely fillip ahead of the COP21 climate talks in Paris starting on 30 November. Already being billed as “the last chance to save the planet” (wasn’t that Copenhagen 2009?), the doom-mongers are out in force. I think we should be building on the fact that national commitments to cut carbon are rising fast. OK, they’re not enough as yet to keep us to 2°C, but those calculations don’t include industrial, regional or city-level commitments.

Speaking of Obama and Copenhagen, it was POTUS who saved the that meeting from complete disaster (a disaster precipitated by the destructive perfectionism of green NGOs according to my friend the environmental journalist Fiona Harvey who witnessed it unfolding first hand). With the other world leaders attending as well as Obama, I’m hoping for some constructive one-upmanship to drive forward commitments. Maybe even David Cameron, who loves striding the world stage with the big boys and girls, will get back into ‘greenest Government ever’ mode.

Yes I’m an optimist, but you know what they say optimists and pessimists have in common? Both their predictions tend to come true.