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Costing 21st Century coastal flooding

By JW Dowey - 05 Feb 2014 14:16:0 GMT
Costing 21st Century coastal flooding

So many cities worldwide are threatened by sea-level rise, resulting from greenhouse gas effect. It's likely that the threat could help energise people to try and prevent the floods before they actually happen this time; City image; Credit: © Shutterstock

The likelihood of damage from rising sea levels is linked to the extent of global warming. The oceans have risen by around 2.5 cm over the last decade, emphasising just how warm the seas and the atmosphere have become already As ice caps glaciers and sea ice show us the trend in rather obvious ways, scientists studying the phenomena have been shocked.

Ordinary people have also been physically affected, of course, by hurricane, typhoon and abnormal flood and drought. There are still politicians in some nations who deny the reality of warming and have not yet been preserved in aspic. The fact is that we can only associate an increase in atmospheric disturbance with the temperature rise.

What really matters is the coastal damage, with millions of square kilometres threatened. The world's major cities are most threatened as they sit on the coast or on tidal rivers. Many countries have regular experience of flat landscapes being flooded by the sea. We have erosion too, in the case of softer rocks and lower-lying cliffs. The dangers are connected with an increase in these occurrences and in their cost. The Global Climate Forum in Berlin, has published this report in PNAS' open access journals, with Jochen Hinkel and many European collaborators who think they can explain the damage and predict some of the costs of worldwide sea-level rise.

For the whole of the 21st century, populations have to be estimated between 2 extremes. Various impacts, too, under the heading of "coastal effects" could take place. Up to 4.6% of the earth's population could be affected on an annual basis. Obviously, higher dykes than those proposed would enhance the whole operation and reduce the effects drastically.

Flood costs also tend to increase as the century progresses, but at a faster rate than the number of people affected. The total range of costs varies from $12 billion to $71 billion. Again these costs depend on the level of protection and the population size. Unconnected national studies produce results that are very much in agreement with these integrated international results.

Uncertainty exists because analysing coastal defences and other factors is essentially a national concern, but the computing of all national figures together gives us a greatly improved "feel" of how events could occur. Given the lack of spending of several governments during current floods, we can expect the very worst!

Anthropogenic effects is a term used to imply human activities. Novel human-induced subsidence caused by the withdrawal of ground water on a river delta could produce catastrophic effects in exactly these areas that the authors are concerned about. Information on these activities is very limited, so that means computer models cannot take them into account. Economic effects can also fail to show properly in the computer models, especially when these unpredictable effects occur.

The success of carbon dioxide prediction models has not then been completely mirrored in the coastal investigations. Some of the data is shown in our article here on predicting carbon dioxide levels.

In the end, we can rest assured that these coastal disasters are in our future, facing us and our descendants, following the mistakes of the last 2 centuries, and that the costs are and will be high!