Although climate change is not the only cause of rising sea levels, it is a significant contributor and depending on the extent of sea level rise and the geographical area affected, there is the potential for serious impacts. While all of the variables affecting sea levels are not completely understood, it is generally agreed by researchers and the Intergovernmental Panel on Climate Change (IPCC) that sea levels are rising and will continue to rise during the 21st century, possibly to levels that will have major consequences in some areas.
While not the only cause of rising sea levels, there are two ways in which climate change is a major contributor. First, the increase in temperatures has accelerated the melting of icecaps and glaciers. These ice bodies discharge into the ocean as they melt adding to the total quantity of water in the sea. Secondly, thermal expansion means that as the temperature of water increases its volume expands resulting in higher sea levels. Houghton (2004) considers thermal expansion is responsible for about a third of the estimated 10 - 20 centimetres sea levels rose during the 20th century.
Impact of Rising Sea Levels
The impact from rising sea levels will depend on how much the sea level rises and the geographical area affected. The worst affected areas will be agricultural communities that heavily populate river deltas and small island nations. Higher sea levels increase the likelihood of flooding with the potential of land being permanently lost to the sea. An IPCC report, Regional Impacts of Climate Change published in 2001, estimates that a 1-metre sea level rise could lead to land losses as great as 30,000 km2 in Bangladesh and 34,000 km2 in Indonesia. As a result agricultural yields and tourism operations will be negatively impacted. Greater coastal erosion will also occur and in some places the intrusion of salt into aquifers will reduce the availability of drinking water.
It is not just low-lying countries that will be affected. The 2030 Research Centre in its report Nation Under Siege - Sea Level Rise at Our Doorstep (2007) outlines that with 53% of Americans living in coastal areas a 1-metre sea level rise makes the country vulnerable to significant property and infrastructure losses as well as large population disruptions.
Potential Rises in Sea Levels
The relationship between land and water is complex and there are still many questions regarding the relationship between climate change and sea levels including other factors that could be contributing to sea level rises. It is also difficult to predict with accuracy the degree sea levels will rise during the 21st century, particularly as sea levels vary throughout the world. However, a study published in Nature Geoscience in 2009 which used fossil coral data and ice-core measurements predicts that sea levels will rise between 7cm and 82cm by the end of the 21st century depending on the degree of warming that occurs. This degree of sea level rise is similar to what has been predicted by the IPCC in its Fourth Assessment Report on Climate Change (2007).
Although the level the sea will rise and the subsequent impacts are not 100% certain, it is agreed that sea levels have risen over the 20th century and will continue to do so during the 21st century. The potential effects of sea levels rises should be factored into climate change discussions at all levels and strengthen the argument as to why carbon emissions need to be reduced.
Sources
United Nations Environment Program. (2009). 2009 Year Book.
Houghton, J.T., ( 2004). Global Warming: The Complete Briefing. 2nd Ed. Cambridge University Press.
Siddall, M., Stocker, T.F., and Clark, P.U. (2009). Constraints on future sea-level rise from past sea-level reconstructions. Nature Geoscience 2, 571 - 575.
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