Tuesday, May 8, 2012

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.

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.

3 comments:

William Connolley said...

> 5.31 million km^2 -- Linear Trend Climatology 1979-2008

You left off 1979-2010 Climatology. Why?

carbon credit investments said...

I am not an expert on this stuff, but have become a recent convert to the fact and reality that extreme climate change is occurring. Now, when you say its a good sign, do you mean the data itself is a good sign, or its just a good sign that the models are working. The latter is good for you guys and for enabling accurate scientific research, but the planet could still be screwed!

Robert Grumbine said...

William:
I went with 30 years, as it's the standard climate period. Did that for both the mean and the linear trend. Since there's no reason to think that the trend is linear, I didn't see a reason to keep updating linear trends year by year from start to present.

carbon:
the 'good sign' is definitely a matter of the models + statistics working moderately well. If they do, then it suggests that we understand something about how this part of the climate system works.

Whether this means good things or bad things for species (like Homo sapiens) that we are interested in is a different question entirely.