Leading Australian scientists have firmed their view on the rate of sea-level rise, in the latest snapshot of this climate change problem.
Over the past 50 years, the global average rise of 1.9 millimetres a year measured in tide gauges has been confirmed in satellite measurements, raising confidence in predictions.
"We are very close to the final answer on this," said oceanographer John Hunter, of the Antarctic Climate and Ecosystems Co-operative Research Centre in Hobart. "Once we do that we can do our modelling for the future much better."
In the ACECRC's Report Card: Sea Level Rise 2012 released today, a dramatic short-term rise was identified north of Australia, where waters rose at around 10mm each year over the past 18 years.
But Dr Hunter cautioned that this was likely to relate to El Nino events, rather than long term sea-level trends.
He said the Australian coasts faced a rise of about the global average rate through the 21st century - meaning sea level would be around 0.38 metres higher in 2090 than it was 100 years earlier.
Thermal expansion - the greater space occupied by hotter sea water - has contributed about 45 per cent of the total rise since 1972, according to the report card.
Melting glaciers and ice caps added another 40 per cent, with most of the remainder coming from ice sheets.
The report card warns that as a rule of thumb, a 0.1m rise in sea level increased the frequency of flooding by about a factor of three.
"This effect is multiplicative so that even a relatively modest increase in mean sea level of 0.5 m will increase the frequency of flooding by a factor of roughly 300," it said.
"This means that an event which presently only happens on average once every 100 years (the '100-year return event') will happen several times a year after sea level has risen by 0.5 m."
Dr Hunter said with new data submissions to the International Panel on Climate Change set to close within weeks, the report card represented the state of play on sea level rise as it was likely to be in the IPCC's 2014 report.
