This weekend marked a victory for the optimists.
Cynics who doubted the international community’s ability to jointly face up to the dominating issue affecting the planet have had free rein since the effective failure of the Copenhagen summit in 2009.
In contrast on Saturday night it took French Foreign Minister Laurent Fabius about six seconds to reverse the frustration of six years by hammering down the ceremonial green gavel and announcing the Paris declaration agreed. He thus at that moment committed 195 countries across the world to joint action on climate change.
Of course we are not out of the woods yet. Firstly, the agreement in Paris does enough only to arrest the pace of climate change, limiting the increase in temperatures to two degrees and aspiring towards 1.5 degrees.
Secondly, just as there is many a slip between cup and lip there is many a gap between aspiration and action, despite the legally binding aspect to the accord once it is ratified. Consider for example the curious case of the United Kingdom the dog that no longer barks. At the time of Copenhagen the UK could be said to have been leading the pack on tackling climate change.
Our targets on carbon reductions were among the most advanced and the plans to deliver them among the most coherent. This applied, in particular, to Scotland where our own Parliamentary Act of 2009 was the most ambitious in the developed world and, notwithstanding constant carping, we are still currently on course to meet our own 2020 target of a 42% reduction in carbon emissions compared to 1990.
However that is where things start to go off the Westminster rails. Long gone are the days when David Cameron was hugging huskies.
Now he jets around Europe in his own plane. The policies which once led the world on renewables are now in total disarray. Now instead we ask the Chinese to finance nuclear power stations.
Meanwhile Climate Change Secretary Amber Rudd has turned the traffic lights on green subsidies to red. Probably worst of all the Tory Government, on the very cusp of the Paris summit, fled the field on the potentially world saving technology of carbon capture. In pulling the rug from the Peterhead project they simultaneously broke their own election manifesto commitment and betrayed Scotland.
Thus ironically when Copenhagen was failing we were ahead of the pack.
Now Paris is succeeding we are being left behind. While the planet rushes towards green energy the UK is running away.
Cameron has just landed his private jet on the wrong side of history.