Scientists have recorded a massive spike in the amount of a powerful greenhouse gas seeping from Arctic permafrost, in a discovery that highlights the risks of a dangerous climate tipping point.

Experts say methane emissions from the Arctic have risen by almost one-third in just five years, and that sharply rising temperatures are to blame.

If the course of human history is any model, then the wheels are already turning on Earth’s sixth mass extinction, thanks to habitat destruction, pollution and now global warming, a scientific analysis of millions of years of data revealed Friday.

That means North American mammals are well on the way - perhaps as much as half way - to a level of extinction comparable to other epic die-offs, like the one that wiped out the dinosaurs.

As the Copenhagen meeting on climate change opens, we are getting mixed signals. At one extreme are the “disbelievers,” who say that serious consequences from global warming, if it is really happening, are still decades away so why should people be saddled with higher energy costs now. If the polls are correct the disbelievers now constitute a majority of the American electorate.

At the other extreme are the climate scientists who are telling every media outlet that will listen that the proposals being discussed at Copenhagen are nowhere near enough to save mankind from destruction. Some are saying that a five degree Centigrade increase in the average global temperature may be enough to do in mankind. Food will no longer grow in sufficient quantity to keep all 8 billion of us fed.

Since the 1997 international accord to fight global warming, climate change has worsened and accelerated — beyond some of the grimmest of warnings made back then.

As the world has talked for a dozen years about what to do next, new ship passages opened through the once frozen summer sea ice of the Arctic. In Greenland and Antarctica, ice sheets have lost trillions of tons of ice. Mountain glaciers in Europe, South America, Asia and Africa are shrinking faster than before.

The world is much closer to running out of oil than official estimates admit, according to a whistleblower at the International Energy Agency who claims it has been deliberately underplaying a looming shortage for fear of triggering panic buying.

The senior official claims the US has played an influential role in encouraging the watchdog to underplay the rate of decline from existing oil fields while overplaying the chances of finding new reserves.

The allegations raise serious questions about the accuracy of the organisation’s latest World Energy Outlook on oil demand and supply to be published tomorrow – which is used by the British and many other governments to help guide their wider energy and climate change policies.