This blog is mostly aimed at a source of criticism and fact checking for the blog 'real science' run by someone who goes by the name Steven Goddard. It is intended that material presented here is informative, neutral, impersonal and well sourced such that any of my claims can be checked and criticized in their own right if necessary.

Monday, 9 September 2013

Sea ice in 1923

Note that Gavin seems to be doing a pretty good job of defending himself:

Gavin asked whether he thought there was less ice in 1923 or today? Steven replied with a historical weather review article from November the previous year. The article was very interesting and talked mostly about how the sea ice had receded significantly compared to previous years, and of a warming. Observations such as open water to the 81st parallel were made. The problem here is; steven is not answering Gavins question. A sea ice recession in the twenties does in no way prevent sea ice extent from being less now than it was then, and detail from the actual newspaper doesn't help so much either (for example there is open water to the 81st parallel now on the Atlantic side). A direct comparision is needed, and this is difficult, as there is a reliance on first hand observations such as shipping data; unlike the satellite record now the conditions in the arctic are much less well known. However I give two sources that we may at least get an indication of the differences; the first is from the danish meteorological institute (DMI)

The white area is the presumed arctic sea ice extent in August 1923. It is significantly greater extent-wise than 2013 when taken on value. However the red areas are the most important, as they were direct observations taken during that year, so we can be confident they are reasonably accurate. We see a few interesting features like ice in the kara sea north of novaya zeymla and in the chuckini sea that definitely was not present this August. On this evidence alone we might conclude that 2013 does have less ice (in August at least). The longer term time series (some of which I posted in the previous post back this up). Notice that open water is present to 80N, and probably 81N (you can see the boundary clearly north of Svalbard). These days having open water north of 80 degrees is not that much of an achivement.

The other map is from the J walsh monthly series


More information about the J walsh series may be found here:

I think when you look at publications based on long term sea ice history (some have been given in the previous post) I think it is very reasonable to conclude the sea ice extent in 2013 is less than it was in 1923. Not that I think that the contents of this blog post would be enough to meet the standards of evidence, but I think time series constructed in journal articles are pretty rigorous and convincing (e.g m Kinnard et al., 2008).

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