Can we expect 4 metres of sea level rise by 2050?
In a recent ABC (Aus) Radio interview James Hansen, who is arguably the most prominent climate scientist in the world, said that attempting to limit the temperature to a rise of 2C was far too high and at this level we may expect sea levels to rise by “several metres” by mid-century. There is a huge gap between Hansen’s comments on sea level rise and the latest IPCC report, but the IPCC only report on what they can prove and they specifically said that there were aspects of the Antarctic concerning ice shelf disintegration and ice sheet thinning that were poorly understood and could not be reported on.
There are still no reports that can model this rate of sea level rise so what are the components that draw Hansen to those conclusions, because he also stated “The ice sheets are losing mass faster and faster, with a doubling time of about 10 years”.
If you take the existing rate of sea level rise of 3.1 mm a year and double it every decade you get to a figure of around 1.7 metres rise which is still not “several metres” by mid-century. So what could it be?
If you take the existing rate of sea level rise of 3.1 mm a year and double it every decade you get to a figure of around 1.7 metres rise which is still not “several metres” by mid-century. So what could it be?
Here I think we are looking at the thinking of informed scientists who can see and know what is happening, but do not have the resources or the time for data sets to prove what is happening.
Several things we do know and one is that the loss of ice mass is accelerating and as Hansen said the rate is doubling every decade. The second is that the ice shelves are thinning fast and as an example Pine Island ice shelf, which is still vast and hundreds of metres thick, is now in terminal decline.
Several things we do know and one is that the loss of ice mass is accelerating and as Hansen said the rate is doubling every decade. The second is that the ice shelves are thinning fast and as an example Pine Island ice shelf, which is still vast and hundreds of metres thick, is now in terminal decline.
The cause of this is that the sea water around Antarctica has a temperature of minus 1.8C and will not melt the ice shelves but the deeper water, although very cold, is plus 2C and will melt ice rapidly. Water has a thermal conductivity rate about 20 times more than air so it is an important factor. The top of this deeper water used to be a 1000 metres below the surface but has been rising at 200 to 300 metres a decade and in places is now only 300 metres from the surface and this puts it just within reach of the bottom of the ice shelves. If there is a canyon in the sea bed this warmer water can get in under the ice shelf and start to melt the whole shelf. This is what is happening to Pine Island and also the Totten ice shelf.
These vast ice shelves are held in place by their grip on the land and are holding back the glaciers from where their mass comes. When the ice shelf disappears the glacier starts to slip down the slope towards the sea like custard on a plum pudding and several are doing that already.
With the effect of Global warming the earth’s temperature has raised 0.9C but this is an average of the whole planet and the poles are warming much faster than the average. In some places this is putting more snow on to the continent but around the edges and in West Antarctica in particular the warmer atmosphere is melting the ice from its surface. This has been thinning Larsen C ice shelf and it now has a big crack in it. Larsen A and B have already disintegrated so all eyes are on Larsen C to see what happens.
With the effect of Global warming the earth’s temperature has raised 0.9C but this is an average of the whole planet and the poles are warming much faster than the average. In some places this is putting more snow on to the continent but around the edges and in West Antarctica in particular the warmer atmosphere is melting the ice from its surface. This has been thinning Larsen C ice shelf and it now has a big crack in it. Larsen A and B have already disintegrated so all eyes are on Larsen C to see what happens.
These are the mechanisms which can cause a catastrophic collapse of Antarctica ice shelves and glaciers and much of it is has already started. Similar things are happening in Greenland.
The amount of water held in ice in West Antarctica is enough to raise sea levels worldwide by six metres, East Antarctica sixty metres and Greenland seven metres so the figures are vast but we only need one metre to cause so much infrastructure and farmland to be flooded that it will cause economic collapse of most countries including the USA, the UK, Holland, China, Bangladesh and many small island nations..
The amount of water held in ice in West Antarctica is enough to raise sea levels worldwide by six metres, East Antarctica sixty metres and Greenland seven metres so the figures are vast but we only need one metre to cause so much infrastructure and farmland to be flooded that it will cause economic collapse of most countries including the USA, the UK, Holland, China, Bangladesh and many small island nations..
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