While the global increase of temperature due to our emissions of greenhouse gases into the atmosphere is more or less undisputed among climate researchers, the consequences of the global warming are less clear. Sea-level will rise, but whether we look at half a meter or one and a half meters at the end of the century, is not yet predictable. In terms of impacts on coast and its cities around the globe, these figures correspond to "severe" and "devastating", respectively.
The international project Ice2sea began in 2009 in response to the most recent report of the Intergovernmental Panel on Climate Change (IPCC). The 2007 report identified the unknown rate of loss of ice from Antarctica, Greenland and worldwide glaciers as being the largest uncertainty of sea level rise. The other important cause for sea level rise due to global warming is the thermal expansion of the oceans, which is relatively predictable.
With about 10 Mio € funding from the European Commission, glaciologists, climate scientists and ocean scientists are working together across 13 countries, from Chile to Antarctica to Norway, compiling and analysing data. Using satellite imagery and numerical simulations of ice behaviour, they try to match past and present ice and sea conditions on computer simulations. Then by running these climate models into the future they end up with a set of possible projections.
"Confidence in predicting the future lies in essentially being able to predict the present and the past... Running models using past figures and seeing what changes they produce convinces us that we have some skill in predicting the future," says Dr David Vaughan, coordinator of Ice2sea.
One of the major results of Ice2sea is an improved understanding of how the oceans are affecting the ice sheets. Until recently, researchers assumed that climate change would have an effect on the ice sheet through atmospheric warming melting the surface of the ice. The reality, however, is that ocean changes are responsible for a lot of the effects of climate change. "There is a subtle swing towards understanding that the oceans have a huge role in affecting how the ice sheets are changing," says Vaughan.
In the past, some models have suggested catastrophic rates of sea level rise, with some estimates warning of five metres in 100 years, according to Vaughan. But the Ice2sea team have reduced the hyperbole and are putting an upper limit on what lies ahead with a median projection of 50 centimetres rise over the next 100 years. Depending on local conditions certain regions will see more; others will see less.
Half a metre may not sound like a large rise but small changes can have crescendo effects when out at sea. Even a small rise in the base level of the sea can affect the frequency of damaging storm surges across Europe. A key example is the Thames Barrier, which protects London from floods. Only a very extreme event that - statistically speaking - occurs only once in a millennium may overrun the Barrier. If the sea level rises by 50 centimetres, that level of protection decreases to 1 in 100 years; another 50 centimetres reduces it further to 1 in 10 years.
With figures like these being complacent is not an option. Actions taken now will have long-term implications for sea level. Today's housing in the UK is built to last 150 years, and coastal infrastructures and marine defences are also designed to last for many decades, so knowledge of future conditions for such infrastructure is crucial.
"If we make our decisions too early based on inadequate understanding of what sea level rise is likely to do, we could end up spending money we don't have to spend, or even not spending enough and having to rebuild later on," says Vaughan.
Ice2sea is due to finish in November 2013 with the results playing a key role in the next IPCC report, due out in September 2013.
Project acronym: ICE2SEA
Participants: United Kingdom (Coordinator), Denmark, Greenland, France, Netherlands, Germany, Iceland, Italy, Belgium, Switzerland, Chile, Finland, Norway, Poland
Project N° 226375
Total costs: € 13 635 613
EU contribution: € 9 994 842
Duration: March 2009 to November 2013
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