Betting

July NH Sea Ice.

8 Comments

As some will recall, the bet-challenge for July Sea Ice was to forecast the average JAXA sea ice recorded for the July 18-July 31 inclusive. The results are now in… and the winner is…. DonB who, owing to the small number of betters too all the quatloos!

Here are the more detailed results:

Winnings in Quatloos for NH Ice july, 2010 Predictions.
Rank Name Prediction (10^6 sq km) Bet Won
Gross Net
— Observed 7.37 (10^6 sq km)
1 Don B 7.57 4 40 36
2 climatepatrol 7.61 5 0 -5
3 DeWitt Payne 7.1 2 0 -2
4 Pieter 7.643 3 0 -3
5 John Norris 7.778 5 0 -5
6 Joel Heinrich 7.831 5 0 -5
7 YFNWG 7.85 3 0 -3
8 Lord Soth 6.84 1 0 -1
9 Robert Leyland 8.001 3 0 -3
10 KÃ¥re Kristiansen 8.01 4 0 -4
11 denis 0.331 5 0 -5

The net winnings for each member of the ensemble will be added to their accounts.

Of course, announcing the winner also give us a result to review the status of the sea ice. I rarely say anything that isn’t rather obvious about NH Ice. The three most obvious points are:

  • As usual, there is less NH Sea Ice present in July than in June.
  • Unlike June, this is not the all time record low for the month; however it’s close!
  • The general trend for July sea ice continues to be down.

Here is a graph of trends which also highlights the July average relative to past averages:




For those who like to see the annual cycle, this is the current (constantly updating) graph from JAXA:



As you can see, this years sea ice extent level crossed over the level from 2007 very near the beginning of July. Will the sea ice extent be preserved during August? Who knows? I’ll post the betting script up– probably tomorrow! Those pondering the fate of ice in August and September might want to examine Tamino’s post discussing the relative magnitudes of ice area and ice extent.

8 thoughts on “July NH Sea Ice.”

  1. The decline in extent during July (i.e. the June 30th extent minus the July 31st extent) was uncommonly low. The weather was not conducive to rapid melt: lots of cloud, and the ice motion was not normal (the Beaufort Gyre and the Trans-Arctic Drift more-or-less shut down for most of the month). However,the remaining ice in the central Arctic is very slushy and broken up, with lots of open leads. Look at a MODIS mosaic to see this for yourself:
    http://rapidfire.sci.gsfc.nasa.gov/subsets/?mosaic=Arctic.2010215.terra.4km

    So the concentration is low – which is very conducive to melt – and the current rate of decrease of extent is pretty high. So I’m still expecting a September low in IJIS extent of somewhere under 5 million square kilometres.

    For day-to-day chatter on the arctic sea ice horse race, from a self-described alarmist, see Neven’s blog on the subject: http://neven1.typepad.com/blog/

  2. In addition to Nick’s suggestion about Neven’s blog, I’d like to add Patrick Lockerby’s Chatter Box as a great Arctic Sea Ice information resource.

    As I’ve watched and charted the Arctic sea ice this summer, I have learned that there is a complex interplay of wind, sea surface temperatures, surface temperature and cloud cover that are all affecting the Arctic sea ice. David Barber (link) has a great video for those who would like to dig into the topic in more detail.

  3. Perhaps I should read the background here, but a some questions came to mind on looking at the monthly trends in the graph in the introduction to this thread.

    1) Are any of these trends over the time period depicted statistically significant?

    2) Are there logical reasons for the apparent upward trend for 2 months and downward for the others?

    3) Are the differences in trends between months statistically significant?

  4. Re: Kenneth Fritsch (Aug 5 09:42),

    If you use the NOAA monthly extent data that goes back to 1979, then the slopes for each month appear to be statistically significant by i.i.d. analysis. I haven’t tested for autocorrelation, but I’ve looked at a few months and the residuals of the OLS linear fit pass the Jarque-Bera test for normality. I’ve set up an individuals control chart for the residuals using the 1979-2008 data to calculate slope, intercept and control limits. Viewed as a process, every month for the last two years has been in control.

  5. DeWitt, are any of the monthly trend differences statistically significant and are some up and some down over the 1979-2008 period?

  6. What does it mean when one notices that one is ending more than their expected share of threads?

  7. “What does it mean when one notices that one is ending more than their expected share of threads?”

    Kenneth,

    It means you are what they call a Thread Killer.

    Hey, don’t feel too bad. I’m what they call a CommitmentPhobe. I’m worse. 😉

    Andrew

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