Every now and then WUWT (http://wattsupwiththat.com/) has these gems of blogposts. This one, posted on May 2, 2012, is a guest post by Frank Lansner:
“Arctic Sea ice data collected by DMI 1893-1961
I came across a number of maps showing Arctic ice extend from 1893 to 1961 collected by DMI in “Nautisk Meteorologisk Aarbog”. Each year DMI have collected information on sea ice extend so that normally each of the months April, May, June, July and August ice extend was published.
There is much more to be said about these, but this is my summary for now. […]” > For the dozens of detailed historic maps and commentary, !–> Continue reading – Check it out = http://wattsupwiththat.com/2012/05/02/cache-of-historical-arctic-sea-ice-maps-discovered
DMI´s compilation shows that sea ice area/extent has declined strongly well before manmade CO2 emissions began to soar dramatically; Clearly it also can quickly recover: Sea ice from a level not far from the 2006 level has recovered very fast 1938-1946, for example . For these and many more observations, see the above blogpost.
THE MAPS –> “Brunnur” in Iceland made these maps available on the net beautifully scanned, they’re all here: http://brunnur.vedur.is/pub/trausti/Iskort/ [iskort = ice map]
These maps clearly illustrate how polar ice fluctuates all the time, with rapid melting (and re-freezing over) observed not just since satellite measurements started in the late 1970s, but off and on much earlier as well. For example from a rather icy 1934 followed by an almost open North-East passage with open waters in the Northern Pacific and East Siberian areas in the late 1930s. Here’s a set of August maps between 1921 and 1946:
Just to pick something rather randomly, compare the beginning of May 2012 (the latest image from the NSIDC down the hill here in Boulder, Colorado), with the DMI map for May 1938, and see how much melted by August in 1938 (in the above image):
- DMI – May 1938 & NSIDC May 2012 next to each other:
74 years later… [Yawn…]
- Left: http://brunnur.vedur.is/pub/trausti/Iskort/Jpg/1938/1938_05.jpg
- Right: See latest at http://nsidc.org/data/seaice_index/images/daily_images/N_bm_extent_hires.png
! -> Good Scientific Sea Ice Information Sources:
- WUWT’s handy Sea Ice Reference Page (linked to a long list of credible data sources (including those below); just the facts, no spin): .
- Cryosphere Today – Arctic Climate Research at the University of Illinois.
- Danish Meteorological Institute.
- National Snow & Ice Data Center (NSIDC), based here in Boulder,CO.
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