Danger on the High Seas: Dr Mark Spalding Highlights the Threat of Rising Seas -- the Potentially Devastating and Likely Impact of a Global Temperature Rise on the World's Oceans. (Climate)

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Over the last century, sea levels worldwide have risen by about 18 centimetres. In certain parts of the world, slow rises or falls in the Earth's crust may mask or exaggerate this change, but the fact of sea level rise is now well documented. The oceans cover seven-tenths of the planet, with an average depth of over 3.7 kilometres. Imagine what it takes to make a perceptible difference, either to the depth, or to the temperature, of that amount of water. Any changes take a long time to occur -- if greenhouse gas emissions were stopped today, sea levels would continue to rise for at least 200 years, though at lower rates. As air temperatures rise so the oceans warm up; and as water warms, so it expands. This `thermal expansion' has driven about 75 per cent of the rise in sea level to date. The rest is from ice-melt, notably from the Antarctic, but also the rapid losses of glacial ice around the world.

Sea level rise has occurred before in geological history, but then human civilisation was not a factor. Now we live on an overcrowded planet, with 39 per cent of us living within 100 kilometres of a coast. …


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