More than 2 million square kilometres of Arctic ice that should be there, is not. A few years ago, United Nations models predicted climate change would lead to ice-free Arctic summers within 100 years.

Now, some scientists say it could melt away completely within the next few 100 weeks. And there is next to no chance it will recover.

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The Arctic ice cap shrunk to its smallest recorded size on August 21, three weeks before the end of the normal melt season. Data from several teams of scientists said the ice cap melted past the minimum records for ice extent and area that were set in 2007 — a year Realclimate.org called “apocalyptic for Arctic sea ice”.

The 2007 melt record was a big surprise to Arctic-watchers and made headlines around the world. That year, unseasonably warm, sunny weather helped drive the ice cover to a record low. But this year, even though the extra-warm conditions were absent, even more ice has disappeared.

Earlier this month, a huge Arctic cyclone — or “Arcticane” — hammered the fragile ice pack for days and the sea ice extent fell dramatically. Such storms are very unusual.

Scientists think warming Arctic sea temperatures and falling land snow cover will make them happen more often.

But the US National Snow and Ice Data Center director Mark Serreze told Climatecentral.org that the Arcticane probably had a minor impact on this year’s big melt. He said a much more important factor is that the Arctic sea ice is so much thinner than before.

Last year, the US Polar Science centre said half the ice cap’s volume vanished in the five years from 2006. Serreze said the ice “has gotten so thin now that large areas completely melt out in summer. We no longer need a ‘boost’ from weather patterns favoring summer ice melt like we saw in 2007.”

The region has warmed much faster than elsewhere on the planet. In March, three scientists wrote that the “Arctic is warming two to four times faster than the global average”.

Less ice in the Arctic means the planet gets warmer still — as the ice retreats, the darker open water will absorb more heat from the sun, which will melt more ice.

But the even bigger problem is that an ice-free Arctic could trigger events that spin global warming into overdrive.

NASA climate scientist James Hansen told Bloomberg on August 17: “Our greatest concern is that loss of Arctic sea ice creates a grave threat of passing two other tipping points — the potential instability of the Greenland ice sheet and methane hydrates.

“These latter two tipping points would have consequences that are practically irreversible on time scales of relevance to humanity.”

By methane hydrates, Hansen was referring to the huge store of greenhouse gases frozen into ice-like crystals on the Arctic sea floor. Scientists think there is so much global warming potential in the methane stored there that, if released, it would cause a planetary mass extinction event.

Huge amounts of methane are also locked in frozen Arctic soils and would be released if the soils were to thaw.

It is not known with much certainly what level of warming might set off the frozen methane time bomb, but the new melt records set in Greenland show its ice sheet is already becoming unstable.

Four weeks before Greenland’s normal melt season ended, scientists reported the melt had already smashed the full season record.

The City College of New York’s Marco Tedesco said on August 15: “This year’s overall melting will fall way above the old records. That’s a goliath year — the greatest melt since satellite recording began in 1979.”

The news backed up satellite readings in July, which said the Greenland ice sheet was undergoing an unprecedented melt. NASA said the satellites showed “97% of the ice sheet surface had thawed at some point in July”.

The UN estimates that the melting of the entire Greenland ice sheet would cause a seven-metre sea level rise.

Until recently, most scientists thought an average world temperature rise of about 3°C was the tipping point for Greenland’s ice sheet. But new research says the ice sheet’s point of no return is much closer — about 1.6°C.

That’s a wicked problem, because world temperatures are on track to shoot right past the 1.6°C danger zone. Australian author David Spratt said in a recent article: “At the current temperature rise of 0.8ºC we may have already reached Greenland's tipping point, and with temperature rises in the pipeline (global emissions still rising and no agreement to reduce them significantly), we are very likely to hit 1.6ºC in two, or three, decades.”

Two years ago Mark Serreze told the Inter Press Agency that “the Arctic summer sea ice cover is in a death spiral. It’s not going to recover”. His warnings, and the warnings countless other scientists have made about the Arctic melt, are being proven right.

Far from being “alarmist”, it turns out climate scientists have been too cautious.

Hansen, famous for his ominous warnings about climate impacts, said in an August 3 Washington Post article that he “had a confession to make: I was too optimistic”.

He said he “failed to explore how quickly that average [temperature] rise would drive an increase in extreme weather … This is the world we have changed, and now we have to live in it.”

If we are to live in this warmer world, then we must do so without illusions. The battle to save the Arctic ice has passed — the next challenge is to stop the loss of Greenland's ice sheet, which means planning to leave remaining fossil fuels in the ground and quickly bring emissions down to zero.

In the end, it also means a break with the profits-first market economy, which is the root driver of the climate problem. Capitalism thrives on waste, growth, disaster and pollution — to put the needs of this system before the needs of the planet means to willfully court disaster.