Tipping Point?

More warnings about the Arctic under siege from the effects of global warming; via The Guardian:

Researchers have uncovered compelling evidence that indicates Earth's most vulnerable regions - the North and South Poles - are poised on the brink of a climatic disaster.

The scientists, at an atmospheric monitoring station in the Norwegian territory of Svalbard, have found that levels of carbon dioxide in the atmosphere near the North Pole are now rising at an unprecedented pace.

In 1990 this key cause of global warming was rising at a rate of 1 part per million (ppm). Recently, that rate reached 2 ppm per year. Now, scientists at the Mount Zeppelin monitoring station have discovered it is rising at between 2.5 and 3 ppm.

[...]

In the last two decades, carbon dioxide levels in the atmosphere have risen from 350 to 380 ppm and scientists warn that once levels reach 500, there could be irreversible consequences that would tip the planet toward disaster: glacier melts triggering devastating sea-level rises and spreading deserts across Africa and Asia.

Scientists and campaigners are desperate for politicians to reach agreements that will prevent the 500 ppm 'tipping point' being breached in the next half-century. These new data suggest they may have a far shorter period of time in which to act.