Since the final climate change episode of ‘Frozen Planet’ aired this week I have encountered three attempts to discredit the science: one statement1 by Nigel Lawson and two articles2, 3 by Chrisopher Booker (the first of which accuses the BBC of presenting a one-sided argument, when if anything they made too much of an effort to be balanced – not once did they blame humans for the changes observed). In what I am sure is a pure coincidence, all of these retorts were commissioned by The Global Warming Policy Foundation. This registered ‘charity’ is a think tank, funded by secret donors, that claims to be:
“open-minded on the contested science of global warming, [but] deeply concerned about the costs and other implications of many of the policies currently being advocated.”
It would be easy to attack Lawson and Booker for some of the comically atrocious statements that they have made in the past: the Guardian’s George Monbiot has written a whole article on the ridiculous claims of Christopher Booker. My personal favourite is a graph of Arctic ice recovery he constructed between September 2007 and January 2008, a graph that seems to prove only one thing: the existence of winter!
Let’s ignore these comic gems though and focus on the science at hand. To be fair, not all of what has been written by these two is a complete lie. They have both, however, approached the facts from incredibly biased viewpoints. Consequently, they have ‘cherry-picked’ only those parts of the evidence that confirms their beliefs, without looking at the broader picture.
I should admit here that Antarctic sea-ice melt is not my area of expertise. However, I do know where to find the appropriate (peer-reviewed) literature on the subject and one thing I have noticed, upon reading it, is that Booker and Lawson repeatedly confuse (deliberately or otherwise) the terms ‘ice-sheet’, ‘ice shelf’ and ‘sea-ice’. So before we go any further let’s define what is meant by each:
– An ice sheet is a mass of glacial ice, formed from snowfall over thousands of years, overlying the land
– Ice shelves are floating ice platforms that form where ice sheets flows onto the ocean’s surface
– Sea-ice is what forms when seawater freezes
Now we have that cleared up, lets look at the science:
Lawson and Booker point out that the Antarctic has experienced, in contrast to the Arctic, a growth in sea-ice, and use this to dispute climate change. Parts of the Antarctic have been getting colder and the area covered by Antarctic sea-ice has shown a net increase of 1% from 1976-20064 (scientists do not know yet, however, if this increase in the area of the sea-ice has been accompanied by any changes in ice thickness). There are two reasons why, in contrast to the Arctic, Antarctic sea ice has grown over the last 30 years. Firstly, the Arctic is a small frozen ocean surrounded by land. The opposite is true of the Antarctic, where a large land-mass, covered by ice, is surrounded by the vast water mass of the Southern Ocean. As the oceans heat up more slowly than the land, sea-ice takes longer to heat up and melt here5. Secondly, parts of the interior of the Antarctic land-mass have in fact cooled. This is due to stronger circumpolar winds around the continent that have resulted in a reduction in the amount of warm air reaching the interior. The stronger winds are due to cooling in the upper atmosphere, which are in turn a result of CFC-related ozone depletion6. One worry is that as the ozone hole gradually repairs, this cooling effect will diminish.
So the amount of sea-ice in the Antarctic has increased slightly, but what about the ice-sheets (these are after all what Frozen Planet claimed were melting): are they growing too? Well no, they aren’t: studies that have used a combination of gravity and altimeter observations (land height measurements) show a net loss of ice from Antarctic ice sheets. This loss has accelerated, from 104 gigatones per year between 2002 and 2006, to 246 gigatones per year between 2006 and 20097. This loss, as was explained in Frozen Planet, is due to the acceleration of the flow of glaciers in western Antarctica; a result of the break-up of floating ice shelves8 which act like a plug, slowing the discharge of glaciers into the Southern Ocean.
Booker further claims that whilst the Arctic is getting warmer, the Antarctic is cooling. As discussed above, some parts of the Antarctic are getting slightly cooler, but there is a very well established overall warming trend: over the last 50 years, average temperatures have increased by about 0.5oC9,10,11.
So, if we look at the overall picture we can see that, whilst there has been a very small increase in the amount of sea-ice in the Antarctic over the last 30 years, the Antarctic land mass is losing an ever increasing amount of mass from its ice sheets each year, and although some parts of the Antarctic are getting slightly colder, the continent as a whole is warming.
Let’s ignore the fact that Lawson and Booker may have an agenda to fulfill. Let’s assume they really do believe what they have written (belief in itself is a very dangerous thing to have in science). What I find so irritating about these attacks on the science is that they have ignored the wider picture of what is going on. There is a danger in science of not looking at the whole body of evidence, of forming an opinion first and then only seeking out the evidence that fits that opinion. Lawson and Booker have identified a small subsection of the available data that suggests the Antarctic is gaining ice and getting colder, and honed in on it at the expense of the wider truth. I will leave it for Booker to have the final word as, when referring to David Attenborough, he unwittingly identifies the flaws in his (and Lawson’s) own reasoning, perfectly, in a single sentence:
“In each case, however, he arranged his evidence in a notably loaded way, carefully omitting much of the information a less selective picture would have included.”
4. Cavalieri, D. J. & C. L. Parkinson, (2008) Antarctic sea ice variability and
trends, 1979-2006. Journal of Geophysical Research 113,
5. The Copenhagen Diagnosis: Updating the World on the Latest Climate Science.
I. Allison et al., (2009) The University of New South Wales Climate Change Research Centre (CCRC), Sydney, Australia, 60pp.
6. Turner, J. et al., (2009) Non-annular atmospheric circulation change
induced by stratospheric ozone depletion and its role in
the recent increase of Antarctic sea ice extent. Geophysical
Research Letters 36, L08502.
7. Velicogna, I., (2009) Increasing rates of ice mass loss from the Greenland
and Antarctic ice sheets revealed by GRACE. Geophysical
Research Letters 36, L19503.
8. Pritchard, H. D. et al., (2009) Extensive dynamic thinning on the margins
of the Greenland and Antarctic ice sheets. Nature, 461, 971-
9. Chapman W.L. & J.E. Walsh, (2007) A synthesis of Antarctic
temperatures. Journal of Climate, 20, 4096-4117.
10. Monaghan A. J. et al., (2008) Recent variability and trends of Antarctic
near-surface temperature. Journal of Geophysical Research,
11. Steig, E. J. et al., (2009) Warming of the Antarctic ice-sheet surface since
the 1957 International Geophysical Year. Nature 457, 459-
David Aldridge has a PhD in Marine Science from The National Oceanography Centre, Southampton. He is now planning his escape from academia. He is the founder and editor of Words in mOcean.
3 thoughts on “The truth about the effects of climate change on Antarctica”
Hey David, this is a nice synthesis. I have recently come across quite a disturbing video (http://www.youtube.com/watch?feature=player_embedded&v=wuj_tlRRQdQ) in which “Lord” Monckton takes on a Greenpeace activist. In a truly patronizing and condescending (politician- style) debate he spews half-truths, most noticeably using Antarctica to validate his claims that globally, sea ice cover has not decreased. Just another example of this mess that, unfortunately, seems to get a lot of publicity. The Lay Person prefers to watch someone get completely ‘owned’ rather than a balanced, intelligent debate. Makes for better viewing. A tragedy of modern society.
Cheers Karl, glad you like it (especially as you’re the ‘ice expert’). I agree with you about your point on intelligent debate. However, if you would like to see ‘Lord’ Monckton get ‘owned’ you could watch this clip:
That is brilliant! Never knew he was such a clown. I hope that Greenpeace woman gets to see this too. Can\t believe how patronizing and condescending he was towards her.