On 31/07/2018 11:53, JGD wrote:
On 31/07/2018 11:36, Alastair wrote:

There is a chart he
http://web.nersc.no/WebData/arctic-r...1_ice_area.png
which shows ice area rather than extent. The ice there is not on a
minimum for time of year. Not sure why.


Simply because ice area and ice extent are different measures and they
never agree exactly. See eg:

http://nsidc.org/arcticseaicenews/faq/#area_extent

The chart corresponding to the area rather than the extent referred to
above is:

https://sites.google.com/site/arctis...a_byyear_b.png


(which really could do with some editing to clarify the colours - there
are now just too many superimposed lines).

On the other hand it does dramatically show the recent lines have not
the slightest inclination to return to the 4 decade 2 Standard Deviation
zone.
I did once go into a graphics package and use find and replace with
white to get some idea of one year's trace, then use Charctic where
there was a lot of overprint.