Responding to the IPCC's influential report on the impact of climate change, Foreign Secretary William Hague said that "Governments everywhere have to act."
It is clear from the IPCC's report that a two-degree increase in the world's temperature would be dangerous, and four degrees would be catastrophic.
But that is the likely trajectory, unless there is unprecedented global co-operation to bring down emissions.
No country would be left unaffected. Governments everywhere have to act.
The UN wants to show the opportunities to engage with the challenges that climate change will bring to produce a more stable economy.
The chances of 'severe, pervasive and irreversible impacts' from global warming are increasing say experts in an influential new UN report.