It has been heralded as an unprecedented achievement. This year the vast majority of the world’s nations have issued pledges, or “intended nationally determined contributions” (INDCs), promising a range of emissions cuts as a foundation for an agreement at the Paris climate conference that opens Monday.

But there’s a problem. These commitments, on their own, only have the potential to forge a path that would limit warming to 2.7 degrees Celsius above pre-industrial levels at best, according to the U.N. And other assessments have been even more pessimistic than that, producing higher estimates like 3.5 degrees Celsius by 2100.

That’s well above the 2 degrees C that has been dubbed the final marker of a climatic “safe” zone. And now, a group of scientists who study the “cryosphere” — all the ice and snow in the Earth’s system, at the poles but also in frozen permafrost and mountain glaciers — have unleashed a stark assessment of just how inadequate these currently pledged emissions cuts are (barring a major enhancement of ambitions in Paris). Indeed, they say that if the INDCs are the end of the story, often irreversible changes will usher in that, unfolding over vast time periods, will dramatically raise seas and pour dangerous additional amounts of carbon into the atmosphere.

“Reacting with ‘too little, too late’ may lock in the gradual but unavoidable transformation of our Earth, its ecosystems and human communities, in a terrible legacy that may last a thousand years or more,” says the document, issued by the International Cryosphere Climate Initiative (ICCI) and reviewed by a number of leading ice scientists focusing on Greenland, Antarctica, permafrost, Arctic sea ice, and more.

At the core of the report is the fundamental observation that while overall global average temperatures may have only risen about 1 degree Celsius so far, that rise has already been magnified greatly in the Arctic region, the Antarctic peninsula, and also in many high altitude areas where there is a large volume of vulnerable ice.

As a result, the experts say, many of these regions are now close to (or even in some cases past) major thresholds that, once crossed, we can’t reverse without the arrival of a new ice age. In many cases, in just the past few years the situation has become considerably more dire for key elements of the cryosphere — especially for the ice sheet of West Antarctica, where many scientists think a threshold leading to irreversible loss may have already been crossed.

So if warming really occurs at the level implied by the INDCs — without dramatic additional steps to cut emissions — the report suggests we can look forward to the following: almost total loss of mountain glaciers around the world; major ice loss from West Antarctica and Greenland; a sea ice-free Arctic in the summer; and a major new source of greenhouse gases wafting out of thawing Arctic permafrost. The latter would be particularly damaging because at a time when human-caused emission levels are still far too high, it would require even steeper cuts to fossil fuel use and deforestation than currently contemplated.

Let’s take some of these problem areas in sequence, starting with the planet’s great ice sheets. West Antarctica may already be destabilized at current levels of warming, but the problems don’t stop there. There’s also Greenland, with its 20 feet worth of potential sea level rise in the form of ice. “The best estimate for the viability threshold of the Greenland ice sheet is around 1.6 degrees above pre-industrial,” said Jonathan Bamber, a glaciologist at the University of Bristol in Britain, on a press call to discuss the ICCI report. “If we go above that, the whole ice sheet becomes a relict of the last interglacial, it is no longer viable.”

The concern is not that this would happen all at once or even in this century, but rather, that it would become locked in to occurring. So the researchers are worried that with the current climate ambitions, we could be committing to many meters of long-term sea level rise. And that’s just the beginning of the consequences of melting a lot of planetary ice.

The report also forecasts that with the levels of warming implied by the INDCs, mountain glaciers around the world — which are often a key source of freshwater to communities — will face a severe threat. “We’re on track at the moment to have most of our mountain glaciers cross the threshold beyond which they’re doomed,” said Graham Cogley, a research with Trent University, on the press call.

And then, well, there’s permafrost — frozen soil spread across vast parts of the northern hemisphere Arctic. In a very troubling finding, the report states that even if global average temperatures are held to just 1.5 degrees Celsius — not a target that’s currently on the table — 30 percent of permafrost today could be thawed at least up through the top several meters of soil. And that would translate, by 2100, into about 50 gigatons of carbon emissions — or more than 180 gigatons of carbon dioxide.

Such numbers would severely restrict current emissions budgets that are at the center of current policymaking and, indeed, of assessments of the INDCs. “These carbon losses from thawing permafrost currently are not accounted for in our global climate models, and they need to be accounted for if we are going to hit our emissions targets,” said Susan Natali, a permafrost expert with the Woods Hole Research Center, who reviewed the permafrost section of the report.

To top it all off, the report also forecasts a continual decline of Arctic sea ice that, thanks to feedback processes, will further warm the region encompassing Greenland and many key mountain glaciers — and the large store of the world’s permafrost. For the northern hemisphere, in effect, the loss of Arctic sea ice further weakens the cryosphere across the board.

The upshot is that we could be on the verge, in just a matter of decades, of causing changes that will be irreversible at the scale of thousands of years.

“Cryosphere climate change is not like air or water pollution, where the impacts remain local and when addressed, allow ecosystems largely to recover,” the report states. “Cryosphere climate change, driven by the physical laws of water’s response to the freezing point, is different.”

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