Sea level rises could have serious ramifications for coral dominated ecosystems such as the Great Barrier Reef, which will transition into non-coral dominated states that will last for centuries, say scientists.

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SYDNEY: Sea levels are set to rise by up to a metre within a century due to global warming, a new Australian report said as it warned this could make "once-a-century" coastal flooding much more common.

The Australian government's first Climate Commission report said the evidence that the Earth's surface was warming rapidly was beyond doubt - with the last decade the hottest on record.

Drawn from the most up-to-date climate science from around the world, the report said greenhouse gas emissions created by human industry was the likely culprit behind rising temperatures, warming oceans, and rising sea levels.

Not inconsistent with U.N. figures

Commissioner Will Steffen said while the report had been reviewed by climate scientists from the Australian science body the CSIRO, the Bureau of Meteorology and academics, some judgments, including on sea levels, were his own.

"I expect the magnitude of global average sea-level rise in 2100 compared to 1990 to be in the range of 0.5 to 1.0 metre," Steffen said in his preface to 'The Critical Decade'.

He said while this assessment was higher than that of the Intergovernmental Panel for Climate Change in 2007, which was under 0.8m, it was not inconsistent with the U.N. body which had said higher values were possible.

Surprisingly large impacts

"We're five years down the track now, we know more about how those big ice sheets are behaving," Steffen told reporters in Canberra.

"In part we have some very good information about the Greenland icesheet. We know it's losing mass and we know it's losing mass at an increasing rate. So that's telling us that we need to extend that upper range a bit towards a metre. Now there are commentators who say it should be even higher than that."

The report said a sea-level rise of 0.5m would lead to surprisingly large impacts, with the risk of extreme events such as inundations in coastal areas around Australia's largest cities of Sydney and Melbourne hugely increased. Steffen said in some instances, a one-in-a-hundred year event could happen every year.

Serious implications for economy

The report found that Australia, prone to bushfires, drought and cyclones, had also likely felt the impact of rising temperatures in recent years. In the last five decades the number of record hot days in Australia had more than doubled, increasing the risk of heatwaves and bush fire weather, it said.

Director of the Global Change Institute at the University of Queensland, Ove Hoegh-Guldberg said, "The report collates information that underpins our current concern about natural ecosystems such as the Great Barrier Reef. This particular ecosystem is under threat from warming sea temperatures and steadily acidifying oceans.

"If these conditions continue, the competitive advantage that reef-building corals enjoy on reefs such as the Great Barrier Reef will tip in favour of less charismatic organisms such as seaweeds and other non-calcifying organisms. This has serious implications for industries such as tourism and fisheries which bring in over $6 billion each year to the Australian economy, and employ over 60,000 people."

Hoegh-Guldberg, who is an expert on coral reefs added, "The threat to ecosystems such as the Great Barrier Reef is real and growing. If we continue along the current business-as-usual pathway, we will soon be at concentrations of carbon dioxide and sea temperatures which we know are harmful to corals and the reef systems they build."