The stated goal of the treaty is “holding the increase in the global average temperature to well below 2 °C above pre-industrial levels and to pursue efforts to limit the temperature increase to 1.5 °C above pre-industrial levels”.

The inclusion of 1.5 °C is extraordinary. Few pundits expected it, going into the climate summit. It would entail total decarbonisation of global energy – almost certainly a 100% global renewable-energy supply – just a few decades from now.

Sceptics