CANBERRA, Dec. 13 (Xinhua) -- Sea-level rise since the Industrial Revolution has been fast by natural standards and may reach 80 cm above today's sea-level by the year 2100 and 2.5 m by 2200 even without development of unexpected processes, according to a new research made public on Friday.
The Australian National University (ANU) said in a press release that a team from the university and the National Oceanography Center, Southampton, studied several million years of rates of sea-level rise to work out the background pattern of natural sea-level rise.
"We knew from geological data that sea-level is likely to rise 9 meters or more as the climate system adjusts to today's greenhouse effect, but the timescale for this rise was unclear," lead author Professor Eelco Rohling of the ANU Research School of Earth Sciences explained.
"The pattern we determined illustrates how fast sea-level might change if only normal, natural processes were at work.
"Put simply, we considered what nature has done before, and therefore could do again."
The background pattern, which Rohling stressed is not to be confused with a model-based prediction, was compared with historical tide-gauge measurements and satellite observations taken since the Industrial Revolution. The research team looked at the speed of the observed changes and whether they were within the normal, natural range of sea-level changes according to their pattern.
Historical observations show a rising sea-level from about 1800 AD. Around 2000 AD, sea-level was rising by about 3 mm per year.
"For the first time, we can see that this modern sea-level rise is quite fast by natural standards: based on our natural background pattern, only about half the observed sea-level rise would be expected," said Rohling.
"Although fast, the observed rise still seems to be just within the natural range."
"While we remain within normal range, our current understanding of ice-mass loss is adequate. If we move beyond the natural range our understanding falls short. We then won't be able to predict how fast or severe future sea-level changes will be."
This research is published in the open-access journal Scientific Reports.