Comments 1 to 10:

1. barry at 15:16 PM on 29 September, 2012
   With all the fulminating in the skeptiverse that there isn't enough attention paid to Antarctic sea ice, I plotted a linear regression for global sea ice data from Jan 1979 to Dec 2011. Global sea ice area has declined by 1.3 million sq km over the satellite period. But I'm an arts guy, so maybe someone with skillz would like to check that out for themselves. Global daily data 1979 to present I wonder what percentage of the 1979 to 1988 annual average this represents. That doesn't speak much to the article here, which is more about the decline in summertime sea ice, and I doubt the slight increase in Antarctic sea ice makes a difference to albedo concerns, but this seemed like a fair place to post this. Is the matter worth a short SkS article?
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2. TomPainInTheAsk at 17:31 PM on 29 September, 2012
   Wow! GREAT video. "Seeing is believing" - even for non-believers, one can hope. I will be recommending this to every UE (Unconvinced by the Evidence) that I know. Thanks, Barry & Peter Sinclair.
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3. barry at 19:02 PM on 29 September, 2012
   A skeptic friend who has posted here did the work for me and says global annual sea ice area has declined by 6.7% from the 1979 - 1988 average.
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4. TomPainInTheAsk at 20:42 PM on 29 September, 2012
   Barry, 6.7% less sea are ice means that much less albedo? Besides the Arctic, what else would this 6.7% include?
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5. barry at 21:33 PM on 29 September, 2012
   Tom, the value is for Arctic + Antarctic annual sea ice - or 'global' sea ice. Antarctic sea ice has increased slightly, but not nearly enough to offset the Arctic decline. Not to be confused with the video above, which is mainly about summertime Arctic sea ice. The Arctic sea ice minimum, taken as the average extent for the month of September, has declined by 36%.
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6. Physicist-retired at 21:55 PM on 29 September, 2012
   I wonder if anyone has seen this new study from Geology: Mild Little Ice Age and unprecedented recent warmth in an 1800 year lake sediment record from Svalbard. In brief, it shows that, since 1987, summers at Svalbard have been 2C - 2.5C hotter than they were during any time in the last 1800 years - including during the warmest parts of the MWP. While this paper doesn't directly address the video above, I think it must have serious implications for Arctic sea ice in general. It might also be a useful addition to the rebuttal on the 'MWP was warmer' article.
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7. Sceptical Wombat at 23:08 PM on 29 September, 2012
   Barry Annual average sea ice is interesting but not very relevant for albedo. The Arctic and antarctic still pretty much freeze over in winter which doesn't keep the sun out because the sun doesn't shine on these places in winter. In fact winter sea ice helps keep the ocean warm by acting like a blanket. What is important is sea ice in spring, summer and autumn, particularly June and July in the arctic and December and January in the antarctic. During those months on clear days the polar regions actually receive more energy from the sun than equatorial regions on similarly clear days. The presence or absence of ice at that time dramatically affects the ocean's albedo. In the arctic sea ice has been declining rapidly in those months and in the antarctic it has barely moved. If you want to see what has been happening to global sea ice I suggest that you try plotting the sum of arctic and antarctic sea ice but giving one of them a six month lag - so as to line up the two winters and the two summers. You will see not much change in winter coverage but a massive change in summer coverage.
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8. barry at 00:01 AM on 30 September, 2012
   SW, "Annual average sea ice is interesting but not very relevant for albedo" I agree, and said as much above. Antarctic summertime sea ice trends are more strongly positive that wintertime, so the massive decline in summer sea ice (pairing North and South) is really all about the Arctic. It is astonishing to think that I may see the Arctic icecap, a continent sized feature of the Earth, disappear during summers within my life-time.
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9. TomPainInTheAsk at 00:33 AM on 30 September, 2012
   Breaking news of another kind of parasol. Yahoo News just posted this, 10 minutes ago: "Asteroid Dust Could Fight Climate Change on Earth" http://news.yahoo.com/asteroid-dust-could-fight-climate-change-earth-132248031.html The Deniers are already swarming in for the attack!
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10. dana1981 at 01:29 AM on 30 September, 2012
    Tom, we cover Antarctic vs. Arctic sea ice here. I believe MarkR is working on an update blog post on the subject too.
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