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Arctic Sea Ice Volume: PIOMAS, Prediction, and the Perils of Extrapolation

Filed under: — group @ 11 April 2012

Guest Commentary by Axel Schweiger, Ron Lindsay, and Cecilia Bitz

We have just passed the annual maximum in Arctic sea ice extent which always occurs sometime in March. Within a month we will reach the annual maximum in Arctic sea ice volume. After that, the sea ice will begin its course towards its annual minimum of both extent and volume in mid-September. This marks the beginning of the ritual of the annual sea ice watch that includes predictions of the extent and rank of this year’s sea ice minimum, as well as discussion about the timing of its eventual demise. One of the inputs into that discussion is the “PIOMAS” ice-ocean model output of ice volume – and in particular, some high-profile extrapolations. This is worth looking at in some detail.

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An Arctic methane worst-case scenario

Filed under: — david @ 7 January 2012

Let’s suppose that the Arctic started to degas methane 100 times faster than it is today. I just made that number up trying to come up with a blow-the-doors-off surprise, something like the ozone hole. We ran the numbers to get an idea of how the climate impact of an Arctic Methane Nasty Surprise would stack up to that from Business-as-Usual rising CO2

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Curve-fitting and natural cycles: The best part

It is not every day that I come across a scientific publication that so totally goes against my perception of what science is all about. Humlum et al., 2011 present a study in the journal Global and Planetary Change, claiming that most of the temperature changes that we have seen so far are due to natural cycles.

They claim to present a new technique to identify the character of natural climate variations, and from this, to produce a testable forecast of future climate. They project that

the observed late 20th century warming in Svalbard is not going to continue for the next 20–25 years. Instead the period of warming may be followed by variable, but generally not higher temperatures for at least the next 20–25 years.

However, their claims of novelty are overblown, and their projection is demonstrably unsound.

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  1. O. Humlum, J. Solheim, and K. Stordahl, "Identifying natural contributions to late Holocene climate change", Global and Planetary Change, vol. 79, pp. 145-156, 2011.

Times Atlas map of Greenland to be corrected

We were pleased to hear from the University of Arizona’s Jeff Kargel that the Times Atlas folks are now updating their atlas of Greenland. As we reported earlier, the first edition was completely in error, and led to some rather bizarre claims about the amount of ice loss in Greenland. Kargel reports that HarperCollins (publisher of the Times Atlas) has now fully retracted their error and has produced a new map of Greenland that will be made available as a large-format, 2-side map insert for the Atlas and will also be available free online. Meanwhile, Kargel and colleagues have produced their own updated small-scale map and have written a paper that includes both their new map and a description of the incident that led up to it. Kargel was instrumental in pushing the cryosphere community to send a strong message to the publishers that they needed to correct their mistake. (A pre-print of the paper, currently under review and under public discussion on Cryolist, is available here.)

Figure 1 in Kargel et al. (2011) generated by a collaboration of the Geological Survey of Denmark and Greenland (GEUS) and the Programme for Monitoring of the Greenland Ice Sheet (PROMICE) with the Polar Geospatial Center Department of Geology and Geophysics, University of Minnesota. Contact: Michele Citterio (GEUS) for questions about the glacier outlines or Paul Morin (UMinn.) for questions about the MODIS base image mosaic.

HarperCollins is to be commended for listening to the scientific community and producing a corrected map. Unfortunately, and despite recent events demonstrating that popular allegations against climate scientists are all wrong, HarperCollins still says on their web site that it’s all the scientists’ fault for not being clear (“The one thing that is very apparent is that there is no clarity in the scientific and cartographic community on this issue”,they write). Hmm. Our own view is that anyone flying over Greenland en route to Europe from North America would instantly have recognized a problem with the Times Atlas (assuming they knew their location of course). As Kargel and colleagues write in their paper:

“Distinguishing manifest, ignorable nonsense from falsehoods that might take root in the public mind is difficult, but the magnitude of and apparent authority behind this particular mistake seemed to warrant a rapid and firm response. The eventually constructive reaction of HarperCollins, which not only withdrew its mistaken claim but also produced a new map to be included in the Times Atlas as an insert, shows the value of such a response. No less than grotesque trivialization, grotesque exaggeration of the pace or consequences of climate change needs to be countered energetically.”

Nevertheless, they caution that “scientists cannot possibly challenge all of the innumerable misunderstandings and misrepresentations of their work in public discourse.”

Well said. Of course, many scientists can do more, and we encourage all of our colleagues to speak publically about their research and, as the international glaciological research community did in this case, to try to correct misconceptions. At the same time, hopefully, HarperCollins will catch on and recognize that being scientifically literate is not just scientists’ responsibility, but is everyone’s responsibility.

Speculative polar cartography

Filed under: — group @ 5 October 2011

Guest commentary from Kevin Brown

The curious mismapping of Greenland’s ice sheet cover by the venerable Times Atlas recently has excited a lot of outraged commentary. But few people noted that this follows an old tradition of speculative cartography of the polar regions. ‘Modern’ mapmakers as early as the 16th century combined real facts and scientific knowledge with fundamental misinterpretations of that knowledge to create speculative mappings of the world’s unknown shores – and nowhere was this more prevalent than at the poles.

Early cartographers had a particularly difficult time mapping the Polar Regions. Factually, they based their maps on reports from mariners who dared sail the dangerous waters. This was supplemented by information from earlier maps, speculations based upon their personal theories of geography, religious beliefs, and the fiscal and political ambitions of their patrons.
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