2011 Sea Ice Outlook Verification

Sometimes time passes faster than you'd think.  I'm sure that's where Einstein got the principle of relativity from.  In any case, I realized that we're about to be submitting our guesses for the 2012 sea ice outlook and I never did get around to examining, on the blog, how our guesses for 2011 did.  In brief, pretty well.

• 7.03 million km^2 -- Climatology 1979-2000
• 6.67 million km^2 -- Climatology 1979-2008
• at least 5.5 million km^2 -- Joe Bastardi at WUWT
• 5.31 million km^2 -- Linear Trend Climatology 1979-2008
• 5.0 million km^2 -- Wang, Wu, Grumbine model, June
• 4.8 million km^2 -- Wu, Grumbine, Wang model, June
• 4.61 million km^2 -- NSIDC observed September Average sea ice extent
• 4.6 million km^2 -- Wu, Grumbine, Wang model, August
• 4.4 million km^2 -- Grumbine, Wu, Wang statistical ensemble, June
• 4.4 million km^2 -- Crandles, L. Hamilton (at Neven's, but also cited in comments here)
• 3.9 million km^2 -- Alastair (in comment here)

As I'd expected,  the statistical ensemble was low, and the Wang et al. model was high.  The June Wu et al model was a touch high, and the August version was right on (given its reporting precision).  Also, and reassuring, is that all our guesses were within 0.5 million km^2 of the observation.  That's what we've estimated as the standard variation in sea ice extent.

It's a good sign that we were within that range.  Also, 0.5 million km^2 is the variability estimated by almost all groups that provide an estimate for it.  Even though that number is suspiciously round, we actually arrived at it by data analysis.  It's a statement of how much the ice pack varies, rather than the quality of the methods.  The quality of the methods is how their error compares to the 0.5.

For the coming year, we've got some modifications in mind (experiments) for the Wu et al. approach, and I've already made some for the statistical ensemble. 

Plus, I'm going to be taking a look, perhaps getting Wu to play too, at whether this past winter's heavy sea ice cover in the Bering Sea was something we could have (or did) estimate in advance.  The model runs are already done.  It's 'just' a matter of analyzing them.