Producing a sensible response to climate change is a marathon effort, but the world took another plod forward this weekend with the publication of one more scientific report. Important as this latest contribution is, the ball and chain around our ankles is the result of politics, not scientific uncertainty. It is worth thinking now about how to unlock the shackles.

The UN-appointed scientists put their fingers on one of the obstacles: the likely impact of climate change on different countries is very uneven. For some areas - Siberia, Canada, Scotland - some warming may be helpful. For many other areas the consequences are likely to be far less welcome, ranging from water shortages to hurricanes and floods.