Coal use will have to be "pretty much" gone by mid-century if the planet is to avoid sea-level rise of more than a metre by 2100 as Antarctic ice sheets disintegrate faster than expected, new modelling by an Australian-led team has found.
On business-as-usual projections, sea-level rise by the end of the century could exceed 1.3 metres compared with the 1986-2005 average, or 55 per cent more than predicted in the Fifth Assessment Report by the Intergovernmental Panel on Climate Change, according to research published in the Environmental Research Letters journal.
"We have provided a preview of what is probably going to be said by the IPCC in the [Sixth Assessment Report]," due for release in 2021, said Alexander Nauels, lead author of the report, and a researcher at Melbourne University's Australian-German Climate & Energy Centre.
"There are really high risks attached to these new findings from more Antarctic contributions," he said.
Recent research indicates Antarctica is more prone than previously thought to ice sheet melting, particularly for land-based ice exposed to warming oceans from beneath.
At the high end of the range for unmitigated emissions, mean sea-level rise could approach two metres by the end of the century, inundating low-lying coastal regions worldwide.
Regional variations caused by different ocean circulation patterns, will see some areas, such as the tropics, endure faster rises than in other parts of the globe.
However, by implementing the Paris climate target of limiting warming to 1.5-2 degrees above pre-industrial levels, sea-level increases could be limited to about half a metre - in addition to the roughly 20 centimetre rise in the past century.
That goal would need cumulative carbon emissions to be limited to 850 gigatonnes, compared with about 554 gigatonnes so far - a tally that is rising about 10 gigatonnes a year.
"Coal as we know it today [without carbon capture and storage] will have to be gone pretty much [by 2050]," Mr Nauels said. "There is no future for fossil fuels, and coal in particular."
Australia's trajectory of emissions may become clearer by the end of this year when the Turnbull government is due to release results of its climate policy review.
Earlier this month, the government launched its National Energy Guarantee which projects emissions would only track the nation's Paris pledge of cutting pollution 26-28 per cent from 2005 levels by 2030. The onus will be to cut emissions in other sectors, such as transport and agriculture, which have few policies in place to curb pollution.
The research paper also incorporated the so-called Shared Socioeconomic Pathways (SSP) that the IPCC will use for its AR6 report to relate sea-level changes to factors such as population and economic growth, and urbanisation.
These pathway, for instance, consider using a price on carbon emissions to nudge behaviour.
"If we have a carbon price of $US100 [per tonne of CO2-equivalent at 2005 terms] in 2050, according to the SSP scenarios, we could limit sea-level rise to around 65cm by 2100," said Carl Friedrich Schleussner from Climate Analytics, and another of the report's authors.
"This is the first time that a study has combined latest sea-level rise modelling with the new scenarios and we can see clear linkages between specific mitigation efforts and sea-level rise impacts."