Sunday, August 19, 2012

Lucia's bet on Arctic Sea Ice

Lucia is taking quatloo bets on the NSIDC average for September 2012. In the linked post, she's looking at some history, and wondering whether it will be a new record low. Her modelling so far isn't sure.

I think there will be a new record. NSIDC, like JAXA, is low and dropping fast.  So I drew some graphs to show some recent precedents.

Firstly, just the conventional full year plot of NSIDC ice extent. I've used rainbow colors for the years, except for 2012 in black.

Next, the same plot but for August and September only. I've marked the 2007 min September average.

Now here is a plot with all years translated to match the August 16 2012 value (a few early years didn't have a Aug 16 reading and are omitted). Again the 2007 min value of 4.28 million sq km is marked, although it hasn't been translated. The idea is to show that the melt from hereon, if following the path of earlier years, would generally go well below 4.28. The exceptions are years before 1995, when there was much less melting overall.

And finally, here is a plot of the September averages, again offset as if each year was starting on Aug 16 from the 2012 value. As you see, if 2012 were not below 4.28, it would be an outlier relative to recent history.

None of which, of course, says that a record is certain.


  1. The race is not always to the swift, nor the battle to the strong, but that's how the smart money bets

  2. I can't see anything wrong with filling the few gaps in the record with linear decrease/increase across the gap. Sure there could be more accurate functions for this but what are they? Anyway, if the gaps are evenly spaced during the year and the freeze vs. the melt seasons, the slight skews introduced in the gaps should cancel each other out.

    1. If you mean to avoid the omission of the Aug 16 matches - yes, any sort of infill would be OK. The years were 1981,1983, 1984 and 1986.

  3. I think Lucia changed her mind ...

    I've been looking at this too. Different method - same conclusion.

    1. Deep,
      Yes, I think yours is more scientific. We'll see soon enough.

      I was impressed with your thorough analysis of the BEST results.