New research into climate change shows melting Antarctic ice could add more to rising sea levels that previously calculated – adding stark emphasis to the call to drastically reduce greenhouse gas emissions.
The study by New Zealand and Australian scientists has been published in this week's Nature journal.
Using state-of-the-art computer modelling, the scientists found the only scenario that didn't lead to large-scale loss of Antarctic ice was where world emissions were significantly reduced beyond 2020, says lead author, Victoria University's Nicholas Golledge.
The 2013 Intergovernmental Panel on Climate Change report predicted that the Antarctic ice sheet would contribute at most only 5cm to global sea-level rise by the end of this century.
But in 2013 there was insufficient knowledge about how the ice sheet might respond to future warming.
"Our new models include processes that take place when ice sheets come into contact with the ocean," Dr Golledge said.
"If we lose these ice shelves, the Antarctic contribution to sea-level rise by 2100 will be nearer 40 centimetres."
Atmosphere warming would need to be kept under 2degC to avoid the loss of the ice shelves and a long-term commitment to many metres of sea-level rise, he said.
"Missing the 2degC target will result in an Antarctic contribution to sea-level rise that could be up to 10 metres higher than today," Dr Golledge said.
"The stakes are obviously very high – 10 percent of the world's population lives within 10m of present sea level."
Without significant reduction in greenhouse gas emissions over the next couple of decades, the widespread melting of the Antarctic ice sheet could become irreversible.
The United Nations Climate Change Conference will be held in Paris later this year, which will aim to get world-wide agreement on limiting climate change effects.
Co-author Tim Naish says in order to restrict global warming to 2degC the Paris meeting must agree to reduce global CO2 emissions to zero before the end of the century.
Dr Golledge said the choice appeared to be mitigating now for the benefit of future generations or adapt to a world in which shorelines are significantly re-drawn.