The major threat of rising sea levels : the science 7


Climate change will have many impacts, we have seen it throughout many articles. However, one of the main consequences didn’t get much attention here : rising sea levels.

But to the research carried out by several institutions – including the OECD and the World Bank – this may displace and even kill millions of people and cause damages worth billions euros.

In today’s article I will tackle the scientific evidence and data and the next two weeks I will present you the implications this may have worldwide.

Since the beginning of the twentieth century, sea levels rose by twenty centimers (eight inches). This might look tiny, but the worrying thing is that specialists noted that the phenomenon doubled recently to reach three millimeters per annum, compared to 1.8 mm before. This contrasts heavily with a quasi stability for the previous millenia.

This wouldn’t be a problem if our civilizations weren’t relying importantly on coastal areas for agriculture, transportation, industry and if more and more people weren’t moving to coastal large areas.

Three causes of this phenomenon can be outlined :

  • The thermal dilation of oceans : oceans are getting warmer each year due to climate change. And the hotter a water is, the bigger its volume.
  • The melting ices of the continents accounts for a quarter of the current situation and this is due to increase much more with global warming.
  • The melting of both the Arctic and Antarctic. Greenland brings a millimeter each five years. Regarding Antarctica, the IPCC is still in doubt. Their next report will certainly brings more data on that.

By the end of the century – and if global warming was to continue – scientists forecast a minimal increase from sixty centimeters to a meter. This may seem little but such levels would cause billion of euros of damages.

One thing would largely increases the threat : storms and floods. These phenomena create waves that can be three meter high.

A OECD report studied over 136 cities in coastal areas with more than a million inhabitants. The results are impressive : At current levels, the assets at risk during this kind of phenomenon are worth 3,000 billion USD. With only a rise of 50 centimeters a centenary flood put at risks assets worth 35,000 billion USD and would concern over 140 million people.

How come ? Let us have a look at New York City. Many key elements of the city (metro, train lines, the three airports… ) are located below a level of three meters above sea levels. A flood of these systems would considerably slow down the economic activity of the city, and thus of the United States of America and the entire world.

Still according to the OECD report, the probability than of the 136 large coastal cities suffer from a centenary flood is 12 percent per annum, going up to 49 percent in five years.

The World Bank presented last year an even more worrying report on how rising sea levels would represent a large threat, and this even without taking into account storms.

To them, rising sea levels between one and three meters by the end of the century are to be considered as realistic. Nasa specialists agree on such figures.

The data is staggering : with such a rise of sea levels, 135 million people would be at risk and 3.2 percent of the global GDP would be destroyed.

With five meters, we go up to 500 million people that would need to be relocated. This again doesn’t take into account storms, which makes only matters much worse.

To conclude : all this can be avoided if climate change is tackled seriously and greenhouse gases emissions cut by the levels recommended by the IPCC specialists.

The data from this article and the two next one comes from the French Magazine Science et Vie and their July 2008 issue (cover pictured right)

Edit : if you want to continue reading on this topic, please check out the two following articles:

If you want to learn out more on this, please refer to :


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