UPDATE: 2/25/16 DMI offers an explanation and an apology here
One of the graphs we have had on the WUWT sea ice page has been the DMI graph showing 30% concentration of sea ice extent, there has been a widening divergence between the two Arctic sea ice extent graphs produced by DMI. WUWT reader David Burton writes:
Until a few days ago, Denmark’s Meteorologiske Institut (DMI) graphed Arctic sea ice extent two ways. They had a graph comparing the current year to the preceding ten years’ “30%+ concentration” Arctic sea ice extent, with coastal zones masked out, by graphing each year in a different color on the same horizontal timescale.
They also had (and still have) a graph comparing the current year to the preceding four years’ “15%+ concentration” Arctic sea ice extent (and I don’t know how they handle coastal zones in that version). In both graphs, the current (partial) year is plotted with a heavier black line.
Until a few days ago, depending on which graph you choose, you could “prove” that Arctic sea ice extent is either the highest (in the “30%+” graph) that it’s been in the last eleven years, or the lowest (in the “15%+” graph) that it’s been in the last five years.
On 2016-02-18 DMI discontinued the “30%+ concentration” version, which showed high recent ice extents.
This is how DMI describe their 30% graph data:
Total sea ice extent on the northern hemisphere since 2005. The ice extent values are calculated from the ice type data from the Ocean and Sea Ice, Satellite Application Facility (OSISAF), where areas with ice concentration higher than 30% are classified as ice.
The total area of sea ice is the sum of First Year Ice (FYI), Multi Year Ice (MYI) and the area of ambiguous ice types, from the OSISAF ice type product. However, the total estimated ice area is underestimated due to unclassified coastal regions where mixed land/sea pixels confuse the applied ice type algorithm. The shown sea ice extent values are therefore recommended be used qualitatively in relation to ice extent values from other years shown in the figure.
Compare the description of the other DMI graph of sea-ice extent at 15% concentration:
Total sea ice extent on the northern hemisphere during the past years, including climate mean; plus/minus 1 standard deviation. The ice extent values are calculated from the ice type data from the Ocean and Sea Ice, Satellite Application Facility (OSISAF), where areas with ice concentration higher than 15% are classified as ice.
The total area of sea ice is the sum of First Year Ice (FYI), Multi Year Ice (MYI) and the area of ambiguous ice types, from the OSISAF ice type product. The total sea ice extent can differ slightly from other sea ice extent estimates. Possible differences between this sea ice extent estimate and others are most likely caused by differences in algorithms and definitions.
Paul Homewood notes on his blog:
Now there may be good reasons for this difference, and it must be pointed out that DMI has never stated that there is any problem with the 30% version, or reason to doubt it.
Assuming both are right, we have a situation where there may be less ice in coastal regions and/or less 15% ice, but more of the 30% concentration. Given the fact that some of the mixed land/sea pixels can confuse the algorithm, there is good reason to think the 30% version is actually more reliable.
But the real problem is that DMI has now withdrawn their 30% graph, offering this explanation:
I have removed the old sea ice extent graphics and the new graphics (http://ocean.dmi.dk/arctic/icecover.php) is now our one and only official sea ice extent.
When I introduced the new graphics I also announced that the old graphics would be removed after some time – and now is the time, sorry.
I spend too much time explaining the differences and it was quite confusing for many – so, I decided to remove the old graphics. However, all the data are available here http://osisaf.met.no/p/ if you would like do the plotting your selves.
The link for the data which they offer is not of any use to laymen, so effectively the DMI has withdrawn this data from the public eye. Now, when the old link is clicked, we get this:
There has been so much skulduggery going on in the climate establishment in recent years that it is hard to avoid the conclusion that this graph has been withdrawn simply because it gives the “wrong” results. I may be being harsh, but if DMI wants to avoid these sort of accusations, the answer is imply to restore the graph, whether convenient or not.
I would tend to agree.
There is clearly no equipment failure, nor computing failure, it’s simply the person in charge of the product has become irritated at having to explain the differences with the 15% graph to the public. Instead of simply creating an explanation page to link in the 30% graph page, he simply disappeared it to make his job easier. That’s some really lazy science, and does not serve the public interest, something DMI is tasked to do by their own mission statement:
Mission and vision
We create and communicate knowledge about weather, climate and seas for the benefit of society.
We are a world-class meteorological institute. We help citizens, public authorities and private companies to transform knowledge into safety and growth.
Whether it is “skullduggery” or not as Homewood notes, climate science has this continuing habit of not showing adverse results, something Steve McIntyre has noted on more than one occasion through the years.
Since we are still learning about sea ice trends, factors, and effects (unless you are one of those who think the science is settled and nothing more to learn) it seems to me that this graph offers an important insight into change in the Arctic that can’t be seen [elsewhere], that may be a precursor to change at the 15% concentration level.
Given their mission statement, I think DMI should restore the graph. For those that agree, you can contact them at: email@example.com If you do email them, please be respectful and cordial; accusations, rants, and anger won’t really mesh with them wanting to cooperate with the public.
UPDATE: The typical haters, such as Neven Acropolis, are making claims in comments that I see this as some sort of “conspiracy”. I do not and any such claim is false and political in nature. I see this as nothing more than a DMI employee who has become annoyed at having to answer questions about the 30% graph, and made a decision to pull it, something supported by the DMI reply email posted by Paul Homewood. In that email DMI doesn’t explain why they’ve chosen to remove it and only make the 15% graph official, only that they have.
WUWT readers may recall that once before I was accused of making conspiratorial thinking when NSIDC’s graph went wonky, even NSIDC told me it “wasn’t worth blogging about” only to have egg on their faces days later when it was clear the satellite data had failed, and it was the result of the instrument on the spacecraft, something I alluded to. That pretty well silenced those people, but of course they never apologized for it.
Given that the DMI 30% graph is made from the same satellite data as the 15% graph, people such as Neven will have a very hard time claiming that somehow the the 30% graph is flawed, and the 15% graph is not. There’s no separate satellite instrument to capture 15% vs. 30%, as that is done in post processing, so we can rule out equipment failure as an issue.
As I noted, Steve McIntyre has shown through the years that there is a tendency in climate science to not publish adverse data and/or results that are inconsistent with conclusions of papers and institutional outlooks. This may be one of those times, or it may simply be a grumpy product manager who is tired of answering questions about it. Hopefully DMI will clarify their position and give a credible explanation as to why they have removed it.
UPDATE2: Commenter “pethefin” notes that DMI has an entire page dedicated to the use of the 30% concentration value that is still operational:
The continuation of 30% product types like this by DMI makes it pretty hard for some people to credibly claim that somehow the 30% graph that was removed was flawed where the 15% graph made from the same satellite data is not.