DMI’s Missing Graph
By Paul Homewood
h/t Dave, Andy and Pethefin
For the last few months, there has been a widening divergence between the two Arctic sea ice extent graphs produced by DMI.
The above chart for Feb 2nd, accessed via the Wayback Machine, is for 30% ice concentration, and shows ice extent at 10-year high levels since October.
This is how DMI describe this 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.
This contrasts strongly with their other version, which looks at 15% ice concentration:
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But the real problem is that DMI has now withdrawn their 30% graph, offering this explanation: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The link for the data which they offer is not of any use to laymen, so effectively the DMI has withdrawn this data from the public eye.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.