Summer break

It'll be very quiet here for the next few weeks.  Even though I'm not in school, summer break is not a bad idea.

Not sure what I'll be doing for my break reading.  Thoughts about good summer reading, for me or others, welcome.

Supporting some good work

Following April's mention of  world autism awareness day in April, I'll mention an effort to improve a school for special needs students.  It is for a school near my sister (see more of her comments about autistic kids at that awareness day note) that includes autistic children:

Create safe, sensory Environments for special needs school children

When will Arctic ice be gone?

The short answer, before I give you all the qualifiers needed to make sense of it, is 2035, give or take 7 years.

The curve above will take some explaining. But first some other important clarifications:

Often, people don't distinguish between types of ice. So you'll hear them talk about 'ice is growing', when what they mean is the center of the Greenland ice cap, or Antarctic sea ice. My comment is specific to Arctic sea ice.

Another trap people fall in to is not paying attention to what sort of statement about ice is being made. There are two parts to this. I'm referring to sea ice extent, not area (well, at 0 extent you also have 0 area, but it's still something to keep in mind). Also, I'm referring to the monthly average for September. If some day showed zero ice cover before my 2035, give or take, that doesn't disprove the prediction. It takes a solid calendar month, September, of no ice to support or refute the prediction.

Then there's the fact that it's a probabilistic prediction.  2035 is the mid-point.  By my estimation method, there's about a 50% chance (54%) that 2035 or some year before that will show zero ice extent for September.  It's only 6% that we'd see zero ice in 2029 (or before) .  And rises to 96% that we'll see zero ice (for the month) in 2042 or before.  The 'or before' is important.

How I got to those predictions turns on the probability thing I mentioned in this year's sea ice estimation note, of it sometimes being easier to work with the probability of something not happening, than trying to figure out directly the chances of it happening.

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Sea Ice Estimations

It's time to start making our estimates of sea ice for September.  I'm submitting two this year to the Sea Ice Outlook, one based on a coupled air-sea-ice model, and one based on a more mature version of my statistical method from last year.  You can join the fun by submitting a guess in the poll I'll put at the bottom of the blog.  Remember, what we're trying to predict is the September monthly average extent.  This is not the minimum daily extent, nor is it the area of ice.  Keep your eye out for these details when comparing what different people say.

I'll start by summarizing predictors:

• Climatology 1979-2000: 7.03 million km^2
• Climatology 1979-2008: 6.67 million km^2
• Linear Trend 1979-2009: 5.37 million km^2
• Wu and Grumbine modeling: 5.13 million km^2
• Grumbine and Wu statistical ensemble: 4.78 million km^2
• Grumbine and Wu best fit statistical: 4.59 million km^2

In doing this year's estimates, I worked with Xingren Wu.  As usual, talking out ideas with somebody made them better.  That is part of why you see two statistical predictions.

The basis of the statistical prediction starts with my eyeball reaction to this figure (this particular copy is from Julienne Stroeve by way of the Weather Underground).  It is comparing IPCC model estimates of ice against observations:

My version for predictive purposes looks like this:

(vertical axis is September average extent in million km^2; the red/orange are observations, blue is the best fit curve.)

So what's going on?

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