posted Sep 20, 2011, 12:45 AM by Aslak Grinsted
updated Sep 21, 2011, 3:20 AM
A new version of the Times Atlas has been made and with it there ofcourse was a press release (see below). Between the old and new editions large changes were made to Greenland. (The ice cover actually appears to be more correct in the old version.) That made it into the press release as a ludicrous 15% loss in ice cover in 12 years! It is true that Greenland is loosing ice due to climate change, but not at such a crazy rate. Among experts on CRYOLIST
this 15% claim provoked a response to try to correct the mistake (See letter on the right). Usually it is very hard to get the same magnitude of exposure to such corrections, but in this case I am actually really positively impressed by the press response
. (I guess it is a good story when some authority is shown to be less than perfect). I am even more impressed by the community who responded so fast to correct this mistake. I like Graham Cogley's take on the events "Fortunately the mistake about the Greenland Ice Sheet is much more obvious and indefensible than the Himalayan error. In the aftermath of ‘Himalayagate’, we glaciologists are hypersensitive to egregious errors in supposedly authoritative sources. Climate change is real, and Greenland
ice cover is shrinking. But the claims here are simply not backed up by
science. This pig can’t fly.
On a side note: The press release also makes another interesting claim: "Modelling predicts that Greenland could reach a tipping point in about 30 years
". This almost sounds like another Himalayagate, but this claim is actually supported by peer reviewed litterature (Mernild et al. 2010
), although 30 years is on the pessimistic end of the range of published estimates (see below). One thing to emphasize that this 'tipping-point' is when we have passed the point-of-no-return where almost the entire ice sheet eventually
will be lost. The keyword here is eventually. It does not say anything about the rate of loss. Still, when this point is passed then we might as well start planning for some huge changes in sea level globally. In this case the 'tipping-point' really means that if Earths climate stays at 2040 levels, then the ice sheet will eventually get lost. Strictly speaking it is not a point-of-no-return, if you consider geo-engineering scenarios where Earth is cooled sufficiently.
Mernild's "30 year" estimate is not the only one out there. In AR4 section 10.7.4.3
the threshold is estimated to be at a global average surface warming of 1.9C - 4.6C over pre-industrial (based on Gregory and Huybrechts, 2006). Temperature projections (AR4 fig 10.26
) are crossing 2C in the period from ~2045-2080 for A1B. So, Mernild's estimate is definitely on the pessimistic end, but not completely out of line with earlier studies.
The source of the error has not yet been identified. The Times Atlas claim that they used NSIDC data to make the atlas, which is a prefectly reasoable source. It would be nice if they would point to a specific NSIDC dataset.
The press release at fault:
found from google's cache since Times appear to have deleted it.
"Atlas turning greenland ‘green’
For the first time, the new edition of The Times Comprehensive Atlas of the World, publishedon 15 September, has had to erase 15% of Greenland’s once permanent ice cover – turning an area the size of the United Kingdom and Ireland ‘green’ and ice-free. This is concrete evidence of how climate change is altering the face of the planet forever –and doing so at an alarming and accelerating rate.
Cartographers of the atlas have sourced the latest evidence and referred to detailed maps and records to confirm that in the last 12 years, 15% of the permanent ice cover (around 300,000 sq km) of Greenland, the world’s largest island, has melted away. Developments are being watched closely. Modelling predicts that Greenland could reach a tipping point in about 30 years, and after that little would preventits ice cap from melting completely. Aptly-named ‘Warming Island’ (Uunartoq Qeqertoq) is the first of possibly many more islands that will bespotted off Greenland as the ice continues to retreat. Several miles long, this island is now large enough tobe shown on The Times Comprehensive Atlas of the World as being separate from the mainland.
The letter from the CRYOLIST experts to the Times
A media release accompanying the publication of the 13th edition of The Times Comprehensive Atlas of the World states that the Atlas is ‘turning Greenland ‘green’’. We are extremely puzzled by this statement and the claim that ‘For the first time, the new edition of The Times Comprehensive Atlas of the World has had to erase 15% of Greenland’s once permanent ice cover – turning an area the size of the United Kingdom and Ireland ‘green’ and ice-free’. We write to point out that a 15% decrease in permanent ice cover since the publication of the previous atlas 12 years is both incorrect and misleading.
Recent satellite images of Greenland make it clear that there are in fact still numerous glaciers and permanent ice cover where the new Times Atlas shows ice-free conditions and the emergence of new lands. Furthermore, the low-lying fringe of the main ice sheet appears to be shown as land, not ice.
A sizable portion of the area mapped as ice-free in the Atlas is clearly still ice-covered. We do not know why this error has occurred, but it is regrettable that the claimed drastic reduction in the extent of ice in Greenland has created headline news around the world. There is to our knowledge no support for this claim in the published scientific literature.
We do not disagree with the statement that climate is changing and that the Greenland Ice Sheet is affected by this. It is, however, crucial to report climate change and its impact accurately and to back bold statements with concrete and correct evidence. The volume of ice contained in the Greenland Ice Sheet is approximately 2.9 million cubic kilometers and the current rate whereby ice is lost is roughly 200 cubic kilometers per year. This is on the order of 0.1% by volume over 12 years. Numerous glaciers have retreated over the last decade, capturing the attention of scientists, policymakers and the general public. Because of this retreat, many glaciers are now flowing faster and terrain previously ice-covered is emerging along the coast - but not at the rate suggested in The Times media release.
Dr. Poul Christoffersen
Prof. Julian Dowdeswell (Director)
Mr. Toby Benham
Prof. Elizabeth M Morris
Dr. Ruth Mugford
Dr. Steven Palmer
Dr. Ian Willis
(Scott Polar Research Institute)
Figure caption: Map of Greenland from the 13th edition of The Times Atlas of the World (left) and a mosaic of MODIS satellite images of the same area acquired on the 14th and 15th August 2011."