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Anthony Watts: Controversy About ‘Record Low’ Arctic Ice Data

Who to believe? It depends on the method, and who thinks their method is most representative of reality. 

Earlier today in part1, I posted about the new record low claimed by NSIDC: Sea Ice News – Volume 3 Number 11, part 1 – new Arctic satellite extent record. The number given is 4.1 million square kilometers:

That of course is being trumpeted far and wide, new life has been given to Mark Serreeze’s “Arctic death spiral” in the media. But, here’s a curiosity, another NSIDC product, the new and improved “multi-sensor” MASIE product, shows no record low at ~ 4.7 million square kilometers:

Note the label at the bottom of the image in red. NSIDC doesn’t often mention this product in their press releases. They most certainly didn’t mention it today.

Another product, NOAA’s National Ice Center Interactive Multisensor Snow and Ice Mapping System (IMS) plot, also shows no reason for claiming a record at all:

Their number is (for 8/22) ~ 5.1 million square kilometers. (NOTE: NSIDC’s Dr. Walt Meir points out in comments that IMS and MASIE use the same base data, but that this one product from IMS only updates weekly, unlike all other sea ice plots which are daily. They should be in sync on the next update cycle, but right now MASIE and IMS should both be at 4.7 million sqkm. -A)

Another curiosity is here. On the NATICE interactive maps on demand page (click on Arctic Daily in the pulldown menu):

The numbers they give for 80% and marginal ice add up to an extent of 6,149, 305 square kilometers.

So who to believe? It depends on the method, and who thinks their method is most representative of reality. Measuring sea ice via satellite, especially when you use a single passive sensor system that has been show in the past to have degradation problems and outright failure (which I was told weren’t worth mentioning until they discovered I was right and pulled the plug)  might be a case of putting all your eggs in one basket. I suspect that at some point, we’ll see a new basket that maybe isn’t so worn, but for now, the old basket provides a comfort for those who relish new records, even though those records may be virtual.

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