Earlier this week, I published a post titled: DMI disappears an inconvenient sea ice graph . Some of the usual folks who police any sea ice discussion went ballistic over the post, and in some ugly blog posts of their own, suggested I and others were engaging in Lewandowsky inspired “conspiracy ideation”. While others may have been, I wasn’t, and made it very clear, but that doesn’t matter to those types, as that sort of stuff is their m.o. when it comes to criticizing climate skeptics.
The fact is though, that DMI did in fact remove the graph from public view, and offered no explanation to the public when they did it. If you aren’t a daily watching sea-ice fanatic like some of the critics, it was easy to miss that the product had been quality control neglected by DMI. Worsening the issue, in an email exchange published in that same WUWT story, one DMI employee was quoted as saying (paraphrasing) “I got tired of answering questions about it so I took it offline”. If there were a lesson of how not to instill confidence in the public when decisions are made to remove data products that have been around for years, suddenly disappearing them with no explanation to the public would certainly qualify as a worst-case example. DMI simply bungled the public face of the decommissioning, there’s really no other way to look at it. Had they done this sort of due diligence before removing the graph, and placed a link to an explanation rather than to the new product with greatly differing values, there likely would not have been the questions about why it suddenly disappeared, and what the possible motives might be. The ham-handed response from the DMI employee did nothing but add suspicion to an already poorly handled situation.
They’ve realized this, and offered an explanation and an apology on their website today. I accept both, which I have republished below.
On a personal note, for those elsewhere in the blogosphere who want to try to convince skeptics that the explanation was rooted in technological problems, I suggest this maxim: “you can catch more flies with honey than vinegar”. The ugly labeling of people with legitimate questions while at the same time trying to convince them of details they may not be aware of was just as badly bungled as DMI’s decommissioning. There’s lessons to be learned all around.
Sea Ice extent – explanation on an appearent [sic] divergence between algorithms.
DMI has removed the old sea ice extent graph to focus the attention on the new graph that is based on data from an improved algorithm.
However, the removal of the old sea ice extent graph was done at an unfortunate time, namely, during a period where it seemed that the new and old ice extent plots disagreed (see figure 1). Naturally this has led to discussion among our dedicated followers, about the “true” ice extent. The apparent elevated sea ice extent in the data from the old extent algorithm was an artifact, caused by a new and higher resolution coast mask.
An off-line update of the old sea ice extent plot (left), where it appears that the sea ice extent is much larger than previous years and
the sea ice extent from the operational algorithm (right), which is DMI’s and the Ocean and Sea Ice, Satellite Application Facility (OSISAF)
Most of our sea ice extent followers know that the old plot includes a coastal mask, inside which sea ice was is accounted for. In summer 2015 this mask was refined and the masked region was subsequently smaller, thus leaving mo re area for classified sea ice and open water. The difference in masked area, before and after summer 2015, is approximately 1.4 million km2. This corresponds to difference of the blue coast lines in figure 2, showing the old and new coastal masks in the left and right panels, respectively. The difference may be difficult to detect on the figure, but the area is quite significant. The increasing sea ice extent that is caused by the new coast mask is not great during summer, because sea ice has a relative short line of contact with land during summer. But the new and finer coast mask will result in increasingly more sea ice, compared to previous years during winter, as the coast line with sea ice contact is increasing. This is the reason for an increasing sea ice extent during current freeze-up period, relative to previous winters. A comparison of the 2015/2016 sea ice extent with previous years does therefore not make sense (see figure 1-left).
Plots of sea ice types February 22 2015 (left) and February 22 2016 (right) using 2 different coast masks.
The mask used before summer 2015(left) is wider than the new mask (right), corresponding to approximately 1.4 million km2 less area under the new mask.
Because of the deprecated status of the old plot in the past year, DMI has not been monitoring these irregularities. The old plot should, of cause, have been removed when the mask was replaced. DMI apologizes for the confusion and inconvenience this has caused.
h/t to mosher