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Estimating Arctic sea ice area 1920-1978 using temperature stations
|Posted by Frank Lansner (frank) on 13th September, 2011|
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Arctic sea ice area in september (minimum) has a lot of attention in the climate debate. However, we cannot know ice areas in the MWP or even in the last warm period, 1920-78. Due to evidence from wood remnants etc, we know, that it has much warmer in Greenland in the MWP than it is today, and thus we have to take for granted, that Arctic ice areas in the MWP was smaller than today.
A little experiment:
Fig1. In order to best possible estimate Arctic sep ice area 1920-78, I chose stations close to the edge of normal summer ice. These stations should be most sensitive to the presence of sea ice near by.
Fig2. Stations near the summer ice boarder on the Eurasian side.
Fig3 Stations near the summer ice boarder on the American side.
Fig4. We see somewhat more heat trend 1920-2010 from the American stations for some reason. (Baselins 1961-90). Using a "conservative" fraction 60% from Eurasian data + 40% American data, i drew the black curve "Arctic ice boarder".
Fig5. I then compared trends in sep ice minimum from NSIDC with the temperature data rom the above stations. A fair agreement. Obviously Ice area in the Arctic is dependant not only of temperatures, but also ocean currents, winds etc. However, one could argue, that the presence of sea ice (regardless why the ice is present) will affect temperatures near by.
So, a rough equation was made between sea ice and temperature, and then used on actual temperature data from the Arctic:
Fig6. Here we see the temperature based estimated of sep Arcitic ice area 1920-1978 stiched to the actual NSIDC numbers 1979-2010. No doubt, the latest years shows the smallest ice extend from 1920 and foreward still, but the period 1934-54 do have quite a few years where temperatures indicates rather small ice areas.
Fig7. In the top 15, several years before 1955 pops up.
Temperautures are taken from unadjusted GHCN + Nordklim.
Why should the relationship between ice area and temperatures in the Arcitc be different today than before 1979?
Last changed: 13th September, 2011 at 16:24:32Back
|The difference North Am vs. Eurasia||By Frank Lansner on 29th September, 2011 at 19:31:22|
|In general, it seems that Canada limits the data avalability from their stations more than USA, Russia and the Danish DMI (Greenland) .
This is not to me a sign of reliability. I do trust Russian and Danish data more than Canadian, for example, when CRU claimed that some nations would not share data, Canada was "too" fast to agree on this.
BUT! Im not at all saying that this is error in data, I just dont rule it out.
But how could we explain a significant diference from one side of the Arctic to the other?
The other issue, the strong temperature rise around 2005: I believe this is due to strong dive in ice area, which again is affected by unusual winds. But these high temperatures are only slightly warmer than the peak around 1940 and thus, perhaps not that unrealistic?
K.R. Frank And thanks for your opinion.
|By Unknown on 28th September, 2011 at 02:32:18|
|The North Am-EurAsian differences suggest some systematic error. Time of day or placement differences. It would be nice to rule this out.
But the early twenty-first century step-change is quite impressive indeed: 1C degree. Yet can a single factor account for it? CO2? Global cloud cover decline (ie, albedo)? (Not alone since this happened over a few years.) Black carbon from China? (The same objection applies.) Wind and current shifts?
While I have not looked at the last in some time, I surmise that only some combination of factors can explain the step-change shift.
Another complementary exercise suggests itself: John Daly compiled arctic data for this time period over a wider range of arctic and near arctic temperature stations. Perhaps comparing that set to this will give worthy clues about what combination of factors best fits the data.