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

Humans are "very close" to triggering irreversible changes in the polar ice sheets of the Earth, said a professor at the University of Otago.

According to a new study, the icecaps of Antarctica and Greenland could collapse even though global warming caused by humans was limited before it exceeded 2 degrees Celsius compared to at the levels of the pre-industrial revolution. They will contract at rates similar to those of the last decade and as soon as possible.

And both have "tipping points" equal to or slightly above 1.5 to 2 ° C that will cause irreversible ice loss in Greenland and the collapse of large watersheds in Antarctica.

This means that both layers of ice are in great difficulty, although we can stick to the objectives of the Paris Agreement, which is to limit the global average temperature to "well below 2 ° C" Preindustrial and continue efforts to limit the increase in temperature to 1.5 ° C levels ".

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Professor Christina Hulbe, of the School of Surveying at the University of Otago, said the work had "a clear message: we are about to bring about an irreversible change in polar caps of the Earth ".

Melting ice is a sign of rising sea level.

Even if we meet the Paris targets and limit global warming, we are still committed to pursuing ice loss in the 21st century and, along with sea level rise, Hulbe said.

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

The review found that the ice sheets would continue to lose mass at a level similar to that of the last decade.

However, he could not rule out that they could collapse even more quickly.

In June, the analyzes showed that the merger rate in Antarctica has tripled since 2012.

Associate Professor Rob McKay, of the Antarctic Research Center at Victoria University in Wellington, said that after the tipping points were reached at each polar ice cap, "the recession could become inextricable".

Like Hulbe, he said, even if the world reached the goals of the Paris climate agreement, we would be extremely close to the point of no return for accelerated withdrawal.

It's serious, but McKay also pointed out that it would not happen overnight.

"Although this fusion occurs over hundreds or even thousands of years, it is clear from these works that the more we exceed the target of 1.5 ° C, the more this accelerated melting of the ice cap will be fast. "

TAPPING POINTS

Hulbe stated that it has been known for some time that the two ice caps were vulnerable to climate change and that the physical processes that governed them had tipping points, thresholds beyond which it was guaranteed that the ice caps glaciers would shrink whatever we do next.

"The processes that matter most are different in the north and south, and the different research groups use somewhat different approaches to represent them in computer models, but all the computer models all go in the same direction: Irreversible ice loss in both Greenland and Antarctica is between 1.5 and 2 ° C. We are already at just over 1 ° C.

"The models diverge, it is the speed with which the layers of ice retreat once the threshold is crossed. The differences between models are useful because they indicate which processes and which regions require further study.

"New Zealand is an international leader in this type of research, we are doing stimulating field work in Antarctica and the Southern Ocean and we are actively engaged in creating better models to predict what is going on. to go through and how that will unfold for us here at home. "

HUMAN ACTIVITY

James Renwick, professor at Victoria University of Wellington: "What happens with ice and climate, it's only a human activity. We are the cause. We have the power to stop doing what we have done for about 100 years. and switch to renewable energy, stop emitting fossil fuels, that's all.

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

"The latest modeling results suggest that in the next 50 years we could reach a threshold where at least the western Antarctic ice sheet will begin to melt irreversibly, and once that has started you will not be able to stop it. – and parts of Greenland ice pack, same story.

"So we could block the rise in sea level by about 5 m, even if we limit global warming to 2 ° C.

Everyday, people emitting greenhouse gases have brought these tipping points closer together, he said.

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

"We can react quickly to show the world what it is possible to do.This argument that" we are tiny to do nothing "does not seem to apply to America & # 39; Cup or Rugby World Cup in some areas, even if we are tiny.

"There is no reason why we can not do this on climate change, renewable energy, smart technologies." It's just a state of mind, it's just a question of will. "

The summary document, which is a summary of current understanding of a topic based on research, was published in the journal Nature.

Professor Tim Naish, of the Antarctic Research Center of Victoria University of Wellington, said that the timing was right, given the recent publication of the IPCC Special Report on "Global Warming at 1.5 ° C "and global warming.

"Without a certain degree of direct carbon extraction from the atmosphere, it is unlikely that we will avoid it."