Farewell sub-400ppm

"We have said goodbye to measurements below 400ppm at Mauna Loa". So has said Professor Richard Betts of the Hadley Centre and Exeter University.

Now I know that there is no particular physical significance to CO2 levels breaching this level but it is of huge pychological importance. There is the terrible prospect of doom-merchants deciding that now nothing can be done to halt catastrophic climate change and we might as well enjoy what little time remains for mankind. 

That would be a massive mistake. Stabilisation at 450ppm is still possible - if increadibly challenging. But even if we don't manage that we still owe it to our children and our children's children to keep trying.