to devise: ontwerpen. engineering: techniek. estuary: riviermond. to exacerbate: erger maken. greenhouse gas: broeikasgas. havoc: vernieling. minds (hier): mensen. occurrence: voorval, gebeurtenis. scheme: systeem. tidal surge: getijdegolf.

Inevitably, the recent Asian tsunami has concentrated minds around the world on the awful possible consequences of a similar occurrence nearer to their homes. But more necessarily, it has also, by extension, concentrated them on the likely consequences of rising global sea levels – a phenomenon which is not a possibility but a present reality. The only uncertainty is how fast they will continue to rise. The most recent scientific thinking is that the threat may have been underestimated. Steps have to be taken.

Of course, the most important steps are those which would drastically reduce the creation of greenhouse gases which cause global warming (which causes the rising sea levels). However, we have done less than a quarter of what is necessary. So in particular parts of the world, other minds are devising engineering solutions to local problems.

Take London, for example. This city is in any case naturally vulnerable to flooding through tidal surges along the River Thames. One flood in the 17th century left the Westminster area under nearly two metres of water. In 1928, 14 people drowned and in 1953 a tidal surge killed 300 people in the Thames Estuary to the east of London. Realisation of the havoc that would have been wrought if this surge had reached London provoked the construction of the Thames barrier, which was completed in 1983.

But this barrier will soon be inadequate. The problem of rising sea levels is exacerbated by the fact that London is sinking anyway (by about 20cm a century). So British scientists are now exploring the possibility of building a new barrier along the Dutch model, which would stretch for almost 16 kilometres across the Thames Estuary. They say that if the more pessimistic scenarios of rising sea levels turn out to be true, something of this kind would have to be in place within 20 years – or central London could be flooded to a depth of two metres within an hour.

Of course, schemes such as this would not solve the real problem. They would just shift them. The water has to go somewhere. The proposed barrier would mean that large parts of Kent and Essex would be subject to devastating inundations. The only full solution is to get rid of greenhouse gases.