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Earth – melting in the heat?

BBC News – October 7, 2005

This article details some of the observed effects of global warming as well as some of the effects for the future.  It is quite light on scientific detail – just a discussion on the empirical observations that bring one to conclude that global warming is real.

Indigenous Arctic peoples will find their food stocks gone, while fresh water supplies in Asia and south America will disappear as the glaciers which provide them melt away; penguins, polar bears and seals will find their habitats gone, their traditional lives unliveable.

There is so much ice here [Antarctic] that if it all melted, sea levels globally would rise hugely – perhaps as much as 80m. Say goodbye to London, New York, Sydney, Bangkok, Rio… in fact, the majority of the world’s major cities.

Parts of it appear to be thickening as a result of snowfall increases. But the peninsula is thinning at an alarming rate due to warming.

Temperatures in the Peninsula appear to be increasing at around twice the global average – about 2C over the last 50 years. Those figures are based on measurements made by instruments at scientific stations.

The ice dumped into the ocean as the glaciers retreat should not make much difference to global sea levels – perhaps a few cm.

The rock on which the West Antarctic ice rests is below sea level – and British Antarctic Survey researchers believe the thinning could be due to the ice sheet melting on its underside.  “It may be that the ocean is warming and that’s causing the ice to melt, but there may be other reasons as well; for example, there’s lots of volcanism in that area and so that could change how much heat is delivered to the underside of the ice sheet.”

If the entire West Antarctic ice sheet did melt, sea levels globally would rise, by around 5m. But at the moment, there is no sign of that happening.  One recent scientific paper attempted to calculate probabilities for how much West Antarctic melting would contribute to global sea-level rises during this century.  The conclusions: a 30% probability of a 20cm rise, and a 5% chance of a 1m rise.

Eastern mass:  “It is not going to happen on any realistic human timescale,” says David Vaughan.  “It’s so cold that you could raise temperatures by 5-10C without having much of an impact; it’s on rock above sea level, so warming in the ocean can’t affect it.”

Their projection is that within about 60 years, there will be no summer ice at all on the Arctic Ocean.

In the last two decades, not only has the area shrunk but the ice has got thinner by about 40%; the prediction is that it will vanish altogether during summers in the second half of this century.

This data deficit has led to a rival theory; that the ice is not melting at all, it is simply piling up in another part of the ocean, perhaps along the north Canadian coast.

The Greenland ice sheet is, after Antarctica, the second biggest expanse of ice in the world. Its fringes expand and contract with the seasons; but images show it is melting more each summer now than a decade ago.

In February 2006 researchers discovered glaciers in Greenland were moving much faster than before, meaning that more of its ice was entering the sea.  In 1996, Greenland was losing about 100 cubic km per year in mass from its ice sheet; by 2005, this had increased to about 220 cubic km.  A complete melt of the ice sheet would cause a global sea level rise of about 7m; but the current picture indicates that while some regions are thinning, others are apparently getting thicker.

Cities like La Paz in Bolivia and Lima in Peru rely heavily on glacial meltwater from the high Andes brought down into dry arid areas.

Switzerland, by contrast, uses meltwater for hydroelectric power generation. If the glaciers disappear, their generating capacity will be very much reduced.

Melting glaciers can form lakes on mountainsides – lakes which can suddenly burst, creating torrential streams which threaten life and property.

Michael Hambrey says these incidents have already caused about 30,000 deaths in Peru. They are also a major issue in the Himalayas, where a programme of work is in place to make the lakes safe.

There seems little doubt that the changes seen in mountain glaciers, however, are going to have an impact on human societies in coming decades, as populations expand and the supply of fresh water shrinks with the ice.

Read the article here.

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