Rising Seas Could Swamp One in 10 People by 2100

Even in the lower ranges of current predictions, it looks increasingly likely that sea level rise will be at least 50 cm (19.6 inches) by 2100, scientists told the Congress, and the upper range of sea level rise could be at least one meter (39 inches) by the end of this century.

This means that if emissions of greenhouse gases are not reduced quickly and substantially, even in the best case scenario rising seas may inundate low lying coastal areas housing about one in every 10 people on the planet.

Aerial view spanning 25 kilometers shows a Greenland glacier melting into a fjiord. (Photo by Giovanni Paccaloni)

Organized by International Alliance of Research Universities, the three-day meeting opened today with more than 2,000 participants. The congress has received almost 1,600 scientific contributions from more than 70 countries, making it one of the world's largest ever interdisciplinary conferences on climate change.

The preliminary conclusions from the congress will be presented Thursday at the closing session and will be developed in a synthesis report to be published in June. The Danish government will give the synthesis report to all participants at the UN Climate Change Conference here in December. At that meeting, governments are expected to finalize a new global climate agreement that will pick up where the Kyoto Protocol leaves off in 2012.

Today, lead speaker in the sea level session, Dr. John Church of the Centre for Australian Weather and Climate Research in Hobart, Tasmania told participants, "The most recent satellite and ground based observations show that sea level rise is continuing to rise at three millimeters per year or more since 1993, a rate well above the 20th century average."

"The oceans are continuing to warm and expand, the melting of mountain glacier has increased and the ice sheets of Greenland and Antarctica are also contributing to sea level rise," said Church.

An earlier study led by Church shows that even a modest sea level rise of 50 centimeters will increase the number of coastal flooding events.

"Our study centered on Australia showed that coastal flooding events that today we expect only once every hundred years will happen several times a year by 2100," Church said.

The last assessment report from the Intergovernmental Panel on Climate Change from 2007 projected a sea level rise of 18 to 59 centimeters (7 to 23 inches). But the report stated that not all factors contributing to sea level rise could be calculated at that time.

The uncertainty was centered on how ice sheets react to the effects of a warmer climate and how they interact with the oceans, explained Eric Rignot, professor of earth system science at the University of California Irvine and a senior research scientist at NASA's Jet Propulsion Laboratory in Pasadena.

"As a result of the acceleration of outlet glaciers over large regions, the ice sheets in Greenland and Antarctica are already contributing more and faster to sea level rise than anticipated," said Rignot. "If this trend continues, we are likely to witness sea level rise one meter or more by year 2100."

Professor Stefan Rahmstorf of the Potsdam Institute for Climate Impact Research (Photo by Lizette Kabre courtesy U. Copenhagen)

"The ice loss in Greenland has accelerated over the last decade. The upper range of sea level rise by 2100 might be above one meter or more on a global average, with large regional differences depending where the source of ice loss occurs," said Konrad Steffen, director of the Cooperative Institute for Research in Environmental Sciences at the University of Colorado, Boulder and co-chair of the congress session on sea level rise.

"Measurements around the world show that sea level has risen almost 20 centimeters (7.87 inches) since 1880," explained Professor Stefan Rahmstorf of the Potsdam Institute for Climate Impact Research, who will give the plenary speech on sea level rise at the congress.

The rate of sea level rise is closely linked to temperature - sea level rises faster the warmer it gets, Rahmstorf explained.

"If sea level keeps rising at a constant pace, we will end up in the middle of that 18-59 centimeter IPCC range by 2100," says Rahmstorf. "But based on past experience I expect that sea level rise will accelerate as the planet gets hotter."

"Sea level is currently rising at a rate that is above any of the model projections of 18 to 59 cm," said Church. "Unless we undertake urgent and significant mitigation actions, the climate could cross a threshold during the 21st century committing the world to a sea level rise of meters."

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