Throughout my 35 years in sustainability it has always seemed odd that while so-called economic rationalism reigned over our political, economic and business worlds, rational thought wasn’t applied to issues like climate change. The risks were always clear, as defined by rational science, while a logical analysis of the economics showed acting early was cheaper than acting late. Yet a strange kind of religious and ideological zealotry took hold, as otherwise sensible, educated people ignored rational thought. It was a failure of reason.

While Copenhagen failed to deliver any agreement however, it may well mark a return to rational thought and with it some profound shifts in markets, politics and our approach to sustainability. Perhaps historians will mark this point and refer to the world BC and AC – Before Copenhagen and After Copenhagen.

What will historians say changed at the end of 2009? And if we could read their conclusions now, would it change our present responses – not as historians but as the creators of that history? Perhaps they will write something like this: