Cartographers remove more ice than climate change

You may have noticed that The Times has just released a new Times Atlas and there has been quite a lot press coverage about their new map of Greenland.  The Times state 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”.

This is quite a statement and has been picked up by a number of other publications including The Guardian (John Vidal of The Guardian has stated that his article was based on promotional material from The Times that supported the launch of the Atlas), The Daily Telegraph and The Scotsman.  This is great publicity for the new map, however there are a growing number of climate scientists who are questioning the accurateness of the new map of Greenland.  The rumblings started on Cryolist, a popular climate science discussion board.  The Times do not provide links to any of the resources that they used to compile the new map which makes it very hard to verify the map.

Members of Cryolist, including a number of prominent Professors of Glaciology, have “submitted a Letter to The Times” voicing their concern and asking for clarification on the sources that were used to create the map.  A bit of digging by the Cryolister’s has produced a mosaic of MODIS satellite images from late August 2011, close to the end of the melt season in Greenland and therefore close to the period of minimum ice extent, which shows that ice is far more extensive than suggested by The Times.

Spot the difference? Excerpt from The Times Atlas and a MODIS image mosaic from August 2011

It will be interesting to see how this pans out.  Certainly the climate scientists do not want incorrect information to be circulated, especially if it shows glacial retreat to be much worse than it actually is.  This could erode public confidence in climate science and provide easy ammunition to climate skeptics.  So the lesson for cartographers might be to ensure that your map is as accurate as possible and to provide references to support your map so that it’s representation can be validated by others.  This is one of the cornerstones of Science and should apply to cartography as well.

You can read more about this on the BBC website or by joining Cryolist.

UPDATE (20/09/2011) :

The Guardian have published an article on the issue.  Details of the letter sent by a number of glaciologists are now emerging (letter copied at end of post) and they state that

  • the ice sheet (2.9m cubic kilometres) is loosing mass at a rate of roughly 200 cubic kilometres per year, giving a decrease of around 0.1% by volume over 12 years.
  • if the figure of 15% was correct (which is disputed), this would equate to roughly 1m increase in global sea levels (based on the current estimates that Greenland Ice mass would contribute around 7m of sea level rise if it were to met entirely)

The Times Atlas are still defending their map stating now that they got the data from National Snow and Ice Data Centre (NSIDC) in Boulder, Colorado.  It has been suggested that The Times Atlas may have misinterpreted ice extent and ice thickness or that they could have just removed ice below the 500m contour line.

Letter to The Times Atlas:


Dear Sir,

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.

Yours faithfully,

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)

Update: 23rd September 2011

The disagreement rumbles on.  In a BBC interview,Sheena Barclay the Managing Director of HarperCollins Geo, faces direct questions about the accuracy of the cartography of the Greenland map.  In this she admits that the 15% figure in the press release was wrong. However, when pushed on the validity of the cartographic representation she points towards the general uncertainty in mapping ice extent and the difficulty of representing this at the scale of Greenland.

Sheena seems uncomfortable answering direct questions with a direct answer and the scientific community have not been appeased by the interview. They still support the view that the map is incorrect.  Mapping ice extent is not all that difficult with modern remote sensing techniques. Ice can be distinguished from snow.  The scientists are not talking about a couple of kilometers difference in the ice edge, they point to the satellite images which show large areas of ice (200km across) now depicted as being ice free. This is clear even on Google Maps which has imagery from 2011.

Here is the BBC’s take on the interview.  Interesting they use the words “politician” and “climb-down”.