1 july 2009

Now is the time to prepare for the great floods

New Scientist editorial, 1 July 2009, issue 2715.

THREE key facts about rising sea levels need to be hammered home to the world's politicians and planners: sea-level rise is now inevitable, it will happen faster than most of us thought, and it will go on for a very long time.

Even if greenhouse gas emissions stopped tomorrow, the oceans will continue to swell as they warm, and as glaciers and ice sheets melt or slide into the sea (see "Going, going..."). The growing consensus among climate scientists is that the "official" estimate of sea-level rise in the last report of the Intergovernmental Panel on Climate Change - 0.2 to 0.6 metres by 2100 - is misleading. It could well be in the region of 1 to 2 metres, with a small risk of an even greater rise. And barring a megaproject to cool the planet, it could take several thousand years for it to reach equilibrium - by which time sea level will be somewhere between 10 and 25 metres higher than it is today.

For many islands and low-lying regions, including much of the Netherlands, Florida and Bangladesh, even small rises will spell catastrophe. Most countries, however, will only lose a tiny percentage of their land, even with a very big rise. The problem is what has been built on that land: large parts of London, New York, Sydney and Tokyo, to mention just a few cities. Unless something can be done, great swathes of urban sprawl will vanish beneath the waves. It will take a massive engineering effort to protect these cities - an effort that may be beyond economies that have been brought to their knees by climate change.

"In a few hundred years, large parts of London, New York and Sydney will vanish beneath the waves"

None of this means we should despair, and stop trying to curb emissions; the more we pump into the atmosphere, the higher and faster the seas will rise. But alongside these efforts, we need to start acting now to minimise the impact of future sea-level rise. That means we must stop building in the danger zone.

Countless billions are being spent on constructing homes, offices, factories and roads in vulnerable coastal areas. For instance, the glittering skyscrapers of Shanghai, China's economic powerhouse, are being built on land that is a mere 4 metres above sea level on average, and which is sinking under the weight of its buildings and as water is extracted from the rocks beneath them.

In cities that have been around for hundreds of years, this sort of development may be understandable. But planning for new coastal developments is to fly in the face of reality. If we want to build a lasting legacy for our descendants, we should do so on the plentiful land that is in no danger from the sea. It is one of the easiest ways to mitigate climate change, and we should be acting on it now.

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