Scientists have issued a warning that regulations outlined in the Paris Agreement won't be enough to stop the collapse of Greenland and Antarctic ice sheets.
Under the Paris Agreement drafted in 2015, countries agreed to limit global warming to less than 2degC than pre-industrial levels.
But a new report from Victoria University and the Universite Libre de Bruxelles published in Nature Climate Change found that both ice sheets may have tipping points at or slightly above the 1.5-2degC threshold.
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Victoria University of Wellington's Professor Tim Naish says the report is "extremely timely given the recent release of the IPCC Special Report on Global Warming of 1.5degC, and especially given that we are close to 1.5degC."
"Without some degree of direct carbon extraction from the atmosphere, we are unlikely to avoid it," he says.
Should the ice sheets collapse, the report says it could lead to irreversible loss of mass and drainage basins. The impact of rising sea levels would be catastrophic for New Zealand.
New Zealand's pledge under the Paris Agreement is to reduce emissions by 30 percent below 2005 levels by 2030. It was revealed last year that the cost to the New Zealand economy to meet Paris Agreement targets will be $1.4 billion every year for a decade.
"We are very close to triggering irreversible change in Earth's polar ice sheets," says Otago University's Professor Christine Hulbe, commenting on the new report.
"The threshold for irreversible ice loss in both Greenland and Antarctica is somewhere between 1.5 and 2degC global mean warming. We're already at a bit more than 1degC warming.
"Even if we meet the Paris targets and keep the warming in check, we're still committed to continued ice loss over the 21st century, and with it continued sea level rise."
Victoria University of Wellington's Rob McKay notes that melting differs between hemispheres, with melting of Greenland controlled by atmospheric warming and Antarctica by oceanic warming.
But the temperature threshold to reach these tipping points in both regions is between 1.5 to 2degC, he says, which "suggests that even if we do meet the Paris climate agreement targets, we will be extremely close to the point of no return for accelerated retreat.
"While this melting will play out over hundreds to thousands of years, it is apparent from this work that the more we overshoot the 1.5degC target, the more rapid this accelerated ice sheet melt will be."
The researchers concluded that urgent research is required on the subject to better improve future projections.
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