July monthly seaice data from NSICD is shown below. I have no idea how this reconciles to the JAXA versions that we’ve been following or to the daily binaries. Both extent and area are shown. The SH anomaly has declined markedly with SH winter and the GLB anomaly is slightly negative.
Climate Audit 
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I do not understand how the one-year downturn can be reconciled with this image.
I guess it’s my lying eyes.
It’s a little hard to tell the point on the graph for the same time as last year. JAXA results 6.72 Mm2 on 8/5/2008 and 5.89 Mm2 on 8/6/2007 for a difference of 0.83 Mm2. That seems to be more or less in line with the picture. You have to compare 8/6/2007 with 8/5/2008 because 2008 is a leap year.
Steve: THis is monthly data. No daily resolution.
He’s talking about the daily data available at the link I posted. I thought, in haste, that the charts showed yearly data in my post.
I find it interesting that the NH sea ice remained more or less constant during the 90’s, when global temps were rising, and that it is now diminishing, just as global temps are themselves on a down trend. I don’t know what this means, if only that melted ice has a lot of latent heat, so maybe the heat lost in the SH goes to melt the NH ice?
Re #4
I don’t know where you get this from but the data indicates that ice extent and thickness have been dropping since before the 90s. Check out Cryosphere today or read some of Maslowski’s papers.
#5
From the data above. What FO says is true. Compute the trend stats from 1990-1998. What Phil is disagreeing with is FO’s choice of 1990 as a starting point. Which is a valid complaint. Nevertheless, FO’s point stands: ice melt did not keep pace with temp rise from 1990-98. Moreover, I think this is a good point in need of explanation.
#5,6
Thanks Bender, that was exactly my point. I was just eyeballing the graphs. There is a clear down trend starting in the early 2000’s, and no clear trend during the 90’s.
I guess it would be interesting to plot sea ice extent vs temperature for the different hemispheres. It seems that they do not correlate that well.
Also, Anthony Watts reports on a paper that sheds some light on the issue.
The other pattern to note above (the one Steve probably picked up on) is the NH-SH divergence. I won’t speculate on my pet theory. (Y’all know what it is already anyways.) The question is, I guess, what does IPCC say about divergence between the two hemispheres. Is this an expected part of the GHG response? Or is it the kind of thing you expect from natural internal variability?
I would ask the “experts” at RC if they didn’t spew such vitriol.
#8 Bender, the “polar seesaw”?
#7 From Watt’s page:
That darn ocean again.
From Wikipedia:
Source is apparently a paper by Henrik Svensmark.
I guess one could argue that if ice melts in the Arctic, it actually cools the water there (much like ice cubes cool the mojito). In the Atlantic, cool water dives deep to the bottom, and quietly travels back south (thermohaline circulation), to re-emerge near the Antarctic. So, with some delay, melting of Arctic ice could possibly end up cooling the Antarctic. That is probably a naive, if not incorrect, hypothesis. I no longer have online access to journals, so can’t do much better. The little I could find about the polar see-saw is that it is still poorly understood. In any case, our knowledge of it is more about longer timescales, but that’s because paleoclimatology rarely has a fine temporal resolution. Model results are contradictory. Some show it, some don’t.
Francois #12,
I would think that at the start of the melting season, ice and water just beneath it are near an equilibrium temperature and the melting during summer of less salty water can’t cause a decrease in water temp.
Deep ocean water, instead, forms when sea freezes because water temperature is dropping and sea salt is extruded
Is it possible that there is some kind of data mix-up here? Presumably ice area and ice extent are to some degree independent, but the two sets of curves displayed here are identical within the width of the line used to plot the data. I superposed a partially transparent copy of one on the other in Photoshop, and after a slight adjustment of the vertical scale, the two sets of graphs coincide perfectly.
The graphs show the extent of the sea ice to be always identical to the area of the sea ice. How can that be?