I’ve been aware of this for a couple of days on our Sea Ice page, but hadn’t done anything about it since I wanted to see if it might change. When blogger Kate of Small Dead Animals noticed it and published on it, I figured it was time to start asking NSIDC some questions.
Compare this NSIDC Arctic Sea Ice extent chart…
…with this from Cryosphere Today:
The NSIDC plot has since intersected the 2007 line, but CT has no new images up since 10-27-10:
It certainly appears that there is more ice in 2010 than 2007 on the Cryosphere Today page. CT hardly ever responds to email, so I didn’t even bother asking them why the discrepancy. NSIDC’s Walt Meier though, takes our concerns seriously and responded rather quickly to my questions:
From: Walt Meier
Subject: Re: you might have a problem
Sent: Oct 29, 2010 8:42 AM
Thanks for the heads up. I looked at it and it doesn’t look like there
is any problem.
As we went through before with Steve [Goddard], looking at the images can be
misleading because they’re not on an equal area projection. There is
more ice in the central Arctic this year, but less in the Beaufort Sea,
Canadian Archipelago, and Baffin Bay. These areas roughly balance each
I also recall Cryosphere Today having an issue of changing their images,
so I don’t know if you can consistently compare them anyway – it looks
like their 2007 image is missing some ice. Attached is our concentration
images from 2007 and yesterday and there doesn’t look like much
discrepancy (apologies for the different image sizes).
I fixed the size differences, and here they are:
Of course we don’t have the daily extent data from NSIDC, since they so far have refused to publish it (they do give monthly though) so, we have to be content with image comparison rather than data comparison with NSIDC.
Walt, as I said before, you really should publish the daily data. Consider how this looks: NSIDC director Serreze screams “death spiral” to the media while at the same time holds back publicly funded data. It is the same sort of bull-headedness that got CRU in deep trouble. – Anthony
UPDATE: Reader Lee Kington provides this blink comparator version: