Sea levels could rise up to 20 metres if Paris climate accord isn't followed, NZ study finds

A Victoria University of Wellington-led study published today in a major academic journal has found global sea levels have the potential to rise up to 20 metres under current atmospheric carbon dioxide levels.

The study was led by Georgia Grant, a recent ARC PhD graduate who is now based at GNS Science. It was funded by the Royal Society Te Apārangi’s Marsden Fund, and involved the ARC's Tim Naish, Gavin Dunbar and Rob McKay, as well as other scientists from GNS Science, Victoria University of Wellington and Waikato University, and from the Netherlands, the United States and Chile.

Research has revealed that 3 million years ago, levels of carbon dioxide in the earth’s atmosphere were similar to today’s levels and subsequently caused a rise in sea levels of as much as 25 metres after a third of Antarctica’s ice sheets melted.

Georgia developed a new method of determining the magnitude of sea-level change through analysing the size of particles moved by waves, as part of her PhD research.

The method was applied to the geological archive from Whanganui Basin on the west coast of New Zealand’s North Island, which contains some of the best evidence anywhere in the world for global sea-level changes.

Tim Naish said the study comes with a stark warning. "If we do not keep our greenhouse gas emissions in line with the Paris Climate Agreement target of two degrees warming, then we may potentially lose not only the West Antarctic Ice Sheet, but also the vulnerable margins of the East Antarctic Ice Sheet,” he said.

“Our new study supports the idea that a tipping point may be crossed if global temperatures are allowed to rise more than two degrees, which could result in large parts of the Antarctic ice sheet being committed to melt-down over the coming centuries. It reinforces the importance of the Paris target."

The latest clue to what these conditions might mean for sea levels has been revealed in a study published in the journal Nature today.

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