The enormous Greenland ice sheet is melting twice as fast as it was a decade ago, scientists say. There are predictions the ice sheet could cross a threshold before the end of this century that will lock the world into a sea level rise of up to seven metres over coming centuries. A sea level rise of just one metre — which could occur in this century — would inundate almost a third of Bangladesh and turn 30 million people people into climate refugees.

250,000 of the estimated 1 million people who fled after Hurricane Katrina will likely not return home. Brown said that makes it the first massive evacuation of what he calls climate refugees — people permanently leaving their homes because of climatic change.

Instead of urgent action from the G7, we are witnessing the worst kind of inertia and backsliding," Dr Leggett charged, and asked, "Will it take waves of climate refugees from tropical islands banging on the doors of the White House before we see any real action?