It is increasingly likely that hundreds of millions of people will be displaced from their homelands in the near future as a result of global warming. That is the stark warning of economist and climate change expert Lord Stern following the news last week that concentrations of carbon dioxide in our atmosphere had reached a level of 400 parts per million (ppm).

Massive movements of people are likely to occur over the rest of the century because global temperatures are likely to rise to by up to 5C because carbon dioxide levels have risen unabated for 50 years, said Stern, who is head of the Grantham Research Institute on Climate Change.

‘When temperatures rise to that level, we will have disrupted weather patterns and spreading deserts,’ he said. ‘Hundreds of millions of people will be forced to leave their homelands because their crops and animals will have died. The trouble will come when they try to migrate into new lands, however. That will bring them into armed conflict with people already living there. Nor will it be an occasional occurrence. It could become a permanent feature of life on Earth.’

The news that atmospheric carbon dioxide levels have reached 400ppm has been seized […]