The Intergovernmental Panel on Climate Change has established a solid basis for both international and national action.

The world's top climate scientists, and a handful of diplomats, have just approved a summary of "policy relevant" conclusions on the physical science of climate change. The most controversial finding of the report is also the most significant one for us.

The "carbon budget" was the last part of the summary to be decided, and the subject of hours of heated discussions in the early hours of Sept 27.