Coastal cities under threat from rising sea levels

Posted by Laura Grant on March 11, 2009
Posted in Green News

greenland-ice
Image: Greeland glacier, Nasa/Wallops

Sea level could rise by a metre or more by the end of the century, according new science presented yesterday at the International Scientific Congress on Climate Change in Copenhagen. This has disastrous implications for the 10 percent of the world’s population, or 600-million people, living in low-lying areas in danger of being flooded.

The new estimates are higher than those in the 2007 assessment report of the Intergovernmental Panel on Climate Change (IPCC) which projected a sea level rise of 18 to 59 centimetres. Scientists at the Copenhagen meeting said that it looked increasingly unlikely that sea level rise would be much less than 50cm by 2100.

Rob Bailey, Oxfam’s climate change policy advisor, said: “These startling new predictions on sea level rise spell disaster for millions of the world’s poorest people. Poor coastal communities in countries such as Bangladesh are already struggling to cope with a changing climate and it can only get worse.

“This must be a wake-up call for rich countries are not doing anywhere near enough to prevent these cataclysmic predictions becoming a reality. Rich countries, who created the climate crisis, must cut their emissions from 1990 levels by at least 40 percent by 2020 and provide the $50-billion that is the minimum needed each year to help the world’s poorest people adapt to the unavoidable impacts of climate change,” said Bailey.

Dr John Church of the Centre for Australian Weather and Climate Research, told the Copenhagen conference: “The most recent satellite and ground-based observations show that sea-level rise is continuing to rise at 3mm/yr 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.”

“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 metres,” said Dr Church.

Eric Rignot, professor of earth system science at the University of California Irvine and senior research scientist at Nasa’s Jet Propulsion Laboratory, said: “The numbers from the last IPCC are a lower bound because it was recognised at the time that there was a lot of uncertainty about ice sheets. The numerical models used at the time did not have a complete representation of outlet glaciers and their interactions with the ocean. The results gathered in the last two to three years show that these are fundamental aspects that cannot be overlooked. 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. If this trend continues, we are likely to witness sea level rise one metre or more by year 2100.”

Measurements around the world show that sea level has risen almost 20 centimetres since 1880, said Professor Stefan Rahmstorf of the Potsdam Institute for Climate Impact Research. These data also show that the rate of sea level rise is closely linked to temperature: sea level rises faster the warmer it gets.

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

According to Dr Church, “Sea level is currently rising at a rate that is above any of the model projections of 18 to 59 cm.”

“Different groups may come to slightly different projections, but differences in the details of the projections should not cloud the overall picture where even the lower end of the projections looks to have very serious effects,” says Konrad Steffen, director of the Co-operative Institute for Research in Environmental Sciences (CIRES) at the University of Colorado, Boulder.

And South Africa?

Last year the City of Cape Town announced that it had commissioned an in-depth study of the implications of sea-level rise on the city. With 307km of coastline the city is particularly vulnerable to a rise in sea level and an increase in the frequency of storm events predicted as a result of climate change.

According to Gregg Oelofse of the city’s strategy and planning department: “Impacts will be experienced across key service infrastructure such as wastewater treatment works, stormwater pipelines, electricity grids and substations as well as roads and rail routes. In addition, residential property and recreational amenities located in the coastal areas are particularly vulnerable.”

The study aimed to identify the risks so the city could begin to plan adaptation and mitigation strategies to minimise the implications of climate change. What did arise from the study was that if the City of Cape Town did not proactively address climate change the consequences could be severe.

According to a report in the Sunday Times last year, Durban has initiated a climate change programme and other South African coastal cities such as Port Elizabeth and East London may also.

Sources: University of Copenhagen, Oxfam, City of Cape Town, The Times.

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