Polar ice sheets can "collapse" even if global warming is limited



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Humans are "very close" to causing an irreversible change in polar ice sheets on Earth, said a professor at the University of Otago.

Antarctica and Greenland's ice sheets may collapse even if global warming caused by humans is limited before reaching 2 degrees Celsius above pre-industrial levels, according to new research. They will shrink at rates similar to those of the past decade and will be possible more quickly.

And both have "inflection points" equal to or slightly above 1.5 to 2C, which will cause irreversible ice loss in Greenland and the collapse of large drainage basins in Antarctica.

This means that both ice sheets are in trouble, even if we can stick to the Paris Accord targets of limiting the global average temperature to "well below 2 ° C above pre-industrial levels and seek efforts to limit the increase temperature to 1,5 ° C above the pre-industrial level ". levels. "

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Professor Christina Hulbe of the University of Otago School of Surveying said the work had "a clear message: we are very close to bringing about an irreversible change in the polar ice sheets of Earth."

Ice sheets in Antarctica and Greenland may shrink at rates similar to those of the past decade, and possibly faster.

JOE RAEDLE / GETTY IMAGES

Ice sheets in Antarctica and Greenland may shrink at rates similar to those of the past decade, and possibly faster.

Melting ice caps means rising sea levels.

Even if we meet the Paris targets and keep the warming under control, we will still be committed to continued ice loss in the 21st century, and so the sea level rise continued, Hulbe said.

"I would add to this caution that some of the tip processes may already have been invoked, at least in some parts of Antarctica, but understanding that in detail requires more work."

The review found that ice sheets would continue to lose mass in a manner similar to the last decade.

However, it can not be ruled out that they can collapse even faster.

In June, the analysis showed that the melting rate in Antarctica has tripled since 2012.

Associate Professor Rob McKay of the Victoria University of Wellington Center for Antarctic Research said that after the inflection points were reached on each layer of polar ice, "the retreat may become inevitable."

Ice and snow in Antarctica, captured by a NASA plane, flew over Operation Icebridge, which observes changes in the ice.

NASA / EARTH OBSERVATORY

Ice and snow in Antarctica, captured by a NASA plane, flew over Operation Icebridge, which observes changes in the ice.

Like Hulbe, he said that even if the world met the goals of the Paris climate deal, we would be extremely close to the point of no return to an accelerated retreat.

Seriously, but McKay also pointed out that this will not happen overnight.

"While this melting will occur over hundreds to thousands of years, it is evident from this work that the further we pass the 1.5C target, the faster the melting of the layers of ice will accelerate."

TIP POINTS

Hulbe said that some time ago it was known that both ice sheets were vulnerable to climate change and that the physical processes that governed them had inflection points – thresholds beyond which ice sheets should shrink, no matter what let's do it next.

"The most important processes are different in the north and south, and different research groups use different approaches to represent them in computer models. But all computer models point in the same direction: the limit for irreversible ice loss in both countries and Antarctica is somewhere between the average global warming of 1.5 and 2 C. We are already warming up a little over 1C.

"Where models diverge is how quickly ice sheets recede when the threshold is exceeded. Differences between models are useful because they show which processes and which regions need more study.

"New Zealand is an international leader in this type of research.We conduct challenging fieldwork in Antarctica and the Southern Ocean and are actively engaged in building better models to predict what will happen next and how it will happen for us here at home "

HUMAN ACTIVITY

Victoria University of Wellington Professor James Renwick: "What is happening to the ice and the climate, is totally down to human activity." We are causing this.Power is in our hands to stop doing what we have done in the last 100 years or more and switch to renewable energy, stop emitting fossil fuels, that's what it's all about.

"This should be another call to action, that humanity has the power to change the way we operate."

"The latest modeling results suggest that at some point in the next 50 years we will be able to reach a limit where at least the West Antarctic ice shelf begins to melt irreversibly. And once started, you can not stop it – and parts of it. Greenland ice sheet, same story.

"So we can be blocking about 5 m of sea level rise, even if we limit global warming to 2C.

Every day, people who emitted greenhouse gases approached these inflection points, he said.

Sea ice breaking up in the Ross Sea, Antarctica.

IAIN MCGREGOR / STUFF

Sea ice breaking up in the Ross Sea, Antarctica.

But New Zealand had the potential to lead the way in climate action.

"We can respond quickly, we can show the world what can be done. The argument that we're small, so we can not do anything, does not seem to apply to the Copa America or the Rugby World Cup. in some areas, even though we are tiny.

"There is no reason why we are not doing this with climate change, with renewable energy, with smart technologies. It's just a mentality, it's just a matter of will."

The review article, which is a summary of the current understanding of a research-based subject, was published in the journal Nature.

Professor Tim Naish of the Antarctic Research Center at Victoria University in Wellington said that it was timely given the recent release of the IPCC Special Report on "Global Warming of 1.5C" and given that the world was close to 1.5C warming.

"Without some degree of direct carbon extraction from the atmosphere, we are unlikely to avoid it."

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