RISING sea levels will certainly have a noticeable impact on most parts of the planet. They are already a serious consideration in Miami and California in the USA, while the south of the UK will struggle in just a few decades as the land is sinking, while the north is rising with the removal of the weight of the ice.

Interestingly we hear more about these places than we do about the more serious problems such as the south Pacific islands that are regularly flooded, the fifth of Bangladesh within 30cm or so of high tides, or that 100 million currently live within a metre of high sea level. Indeed it’s likely that 200 million plus will be living below sea level by 2100.

There’s abundant evidence that even before the sea level rises it has a destructive effect with salt water contaminating the water table and damaging the local agriculture.

Tide gauges show that sea level is rising at an accelerating annual rate, from just over a millimetre in 1950, to three in 2010, and now it’s almost four. This is certain to continue unless action is taken to keep the temperature at or below its current one and a half degree rise. Indeed each five year delay in achieving this ambition will result in at least another 10 cm sea level rise.

At the moment nearly half the rise is due to thermal expansion as the water expands when its temperature increases beyond four degrees C. This is likely to continue for many years as the vast volume of the global oceans can hold its extra energy for very long periods.

The rest of the sea level rise is due to the melting of ice, with rapidly shrinking, and disappearing, glaciers away from polar areas, and the retreating ice sheets in Greenland and Antarctica making a very serious contribution.