History will be made today at a ceremony in New York when countries start to formally sign the Paris climate agreement, which was initially approved in December last year.
As the COP21 climate negotiations go down to the wire in Paris tonight, the UN Secretary General Ban Ki-moon has said the talks have been the most complicated and difficult he has ever been involved in.
There were two different actions over the last few days in Paris, with the same underlying message: as we enter the so-called business end of the COP21 talks, there can be no more false solutions to climate change.
I have a strange feeling today in Paris as the UN climate negotiations open in a tense city, shrouded in clouds of terrorist attacks and early winter darkness. That strange feeling? Optimism.