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Thread: 1400 year Arctic Ice Reconstructions

  1. #1 1400 year Arctic Ice Reconstructions 
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    This last month, Nature published a reconstruction of artic sea ice going back 1400 years.
    http://www.nature.com/nature/journal...ture10581.html

    A good run down of the paper is here:
    "Prior to the recent decline, there were periods of sustained greater sea ice (about 1250 to 1450, and 1800 to 1920) and periods of sustained lesser sea ice (before about 1200). The minimum of sea ice before the industrial revolution was even earlier, around the year 640. There were also two later episodes of sea ice decline, in the late 16th and early 17th centuries, but none of these other declines even comes close to the “falling off a cliff” of sea ice we’re seeing today."
    1400+ Years of Arctic Ice | Open Mind




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  3. #2  
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    "Falling off a cliff" just about covers it, I reckon.


    "Courage is what it takes to stand up and speak; courage is also what it takes to sit down and listen." Winston Churchill
    "nature is like a game of Jenga; you never know which brick you pull out will cause the whole stack to collapse" Lucy Cooke
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  4. #3  
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    That is so dramatic, its almost unbelievable.
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  5. #4  
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    Thanks Lynx Fox - that ought to be clear enough to show that the current trend is not simply a normal outlier of a global climate unaffected by rising greenhouse gas concentrations. Whilst the global surface temperature records have enough year to year and decade to decade variation to give encouragement to those who are determined to dispute the reality of climate change, the world's icy regions show unmistakeable change. It's worth noting that the reconstructions end up closely following that late 20th Century plummet with error bar shrinking so much it is almost obscured by recent observations.
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  6. #5  
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    That is so dramatic, its almost unbelievable.
    The worst of it is only shown when you have a good look at the endpoint on that graph. If finishes before the fantastically precipitous drop of the last 5 years. The least sea ice extent shown is just under 8 million square kilometres.

    http://www.ijis.iarc.uaf.edu/seaice/...e_Extent_L.png

    This graph shows that we're now flirting with half that.

    https://sites.google.com/site/arcticseaicegraphs/

    A great collection of graphs from various agencies reporting on sea ice extent, area and volume. The most alarming ones in my view are those with shading for the 1 & 2 delta ranges. Hardly any of the recent records even touch the bottom edge of those ranges - and they're only from the 30 years of the satellite era. So the ranges include most of the recent years - and each new year's data can't even get within that range.
    "Courage is what it takes to stand up and speak; courage is also what it takes to sit down and listen." Winston Churchill
    "nature is like a game of Jenga; you never know which brick you pull out will cause the whole stack to collapse" Lucy Cooke
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  7. #6  
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    Arctic sea ice extent for March 2014 averaged 14.80 million square kilometers
    from nsidc

    up from record march low which happened in 2006(which does not seem to be reflected in the above chart)

    curiouser and curiouser
    Last edited by sculptor; April 5th, 2014 at 08:43 AM.
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  8. #7  
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    What's curious? You can't surely be suggesting that there's no problem if each successive year is not a new lowest ever record.

    As it is, this year's average March extent is the fifth lowest ever.

    The NSIDC tells us

    Arctic sea ice extent for March 2014 averaged 14.80 million square kilometers (5.70 million square miles). This is 730,000 square kilometers (282,000 square miles) below the 1981 to 2010 average extent, and 330,000 square kilometers (127,000 square miles) above the record March monthly low, which happened in 2006. Extent remains slightly below average in the Barents Sea and the Sea of Okhotsk, but is at near-average levels elsewhere. Extent hovered around two standard deviations below the long-term average through February and early March. The middle of March by contrast saw a period of fairly rapid expansion, temporarily bringing extent to within about one standard deviation of the long-term average.
    Here's their graph showing that.




    Arctic Sea Ice News and Analysis | Sea ice data updated daily with one-day lag


    And if you want a brief summary of the most recent records - up to 4th April - according to IJIS.

    IJIS Extent:

    13,849,934 km2 (04 April)
    (2014 maximum: 14,448,416 km2 on 20 March)

    Down 2,813 km2 from previous day.
    Down 92,742 km2 over past seven days (daily average: -13,249 km2)
    Down 27,240 km2 for the month of April (daily average: -6,810 km2)

    315,270 km2below 2000s average for this date.
    282,310 km2below 2010s average for this date.
    219,520 km2below 2013 value for this date.
    550,075 km2below 2012 value for this date.

    Fifth lowest for the date.

    Fourth lowest April to-date average on record.
    "Courage is what it takes to stand up and speak; courage is also what it takes to sit down and listen." Winston Churchill
    "nature is like a game of Jenga; you never know which brick you pull out will cause the whole stack to collapse" Lucy Cooke
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  9. #8  
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    mostly, I was just offering the null for the chart in post #1
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