Making your own sea ice estimates

The Sea Ice Outlook does accept estimates from outside the professional community.  Maybe not everybody involved is thrilled by this, but I do think it's a good idea from my distant vantage.  And Jim Overland, one of the people behind the SIO, is strongly in favor of it.  (I had a chance to talk with him about the outlook and other ice matters a few weeks ago.)

In the most recent report, there are 3 submissions from 'outsiders' -- Chris Randles (you've seen him comment here as crandles) and Larry Hamilton, both at Neven's Arctic Sea Ice Blog, and one from Wattsupwiththat.

Watts' entry was a poll of readers.  While perfectly legitimate as an entry, it's also perfectly useless scientifically.  One goal of science is to gain understanding of the system in order to spread the knowledge around.  Polling can't be spread.

Much more interesting are Chris's and Larry's methods.  Both are obviously methods of great brilliance, as they currently have the same estimate as I do from my statistical method -- 4.4 million km^2 for this September.  Beyond that, you can read their method descriptions in the Sea Ice Outlook report and start constructing your own method by not making the mistake they and I have made.  Whatever those turn out to be.  Larry Hamilton's write ups (one for ice extent, one for volume) are:
http://neven1.typepad.com/blog/2011/04/trends-in-arctic-sea-ice-extent.html
http://neven1.typepad.com/blog/2011/04/trends-in-arctic-sea-ice-volume.html

And you can also examine model output from the PIPS replacement model ACNFS, PIOMAS, and CFS as a basis for making your own estimates.   (And please do cite others that you know of.)

All are welcome to post your methods here in addition to (or instead of) at the SIO.

Adding to the blogroll

Finally got around, after broken wrist and other hiatus, to adding http://blogs.chron.com/climateabyss/ to the blogroll.  Thanks -M for the suggestion.

Other suggestions welcome.  As always, I aim for sources that lean to the educational -- science content rather than political policy.

2011 Sea Ice Outlooks

For 2011, I added a third method of estimation.  Or, rather, I talked with someone who was using a third method and helped refine it some.  Our guesses are 4.4, 4.8, 5.0 million km^2 for September monthly average sea ice extent as computed by NSIDC.

Again, I'll put our estimates in context of some other estimation methods. 

• Climatology 1979-2000: 7.03 million km^2
• Climatology 1979-2008: 6.67 million km^2
• Linear Trend Climatology 1979-2008: 5.31 million km^2
• Wang, Wu, Grumbine model: 5.0 million km^2
• Wu, Grumbine, Wang model: 4.8 million km^2
• Grumbine, Wu, Wang statistical ensemble: 4.4 million km^2

We normally like 30 years for deciding a trend, but 20 years can be enough.  Since it's far from obvious how to decide what is 'climatology' when climate is changing, taking a few different approaches seems a good idea.  I include a climatology which has a (declining) linear trend on the grounds that there clearly is a declining trend to the sea ice extent, so we expect this year to be lower than last year to some degree (on average).

The two climatology means (22 and 30 years) are relatively close to each other, and are far away from anything we've seen in years.  Taking the 30 year trend, from the first 30 years of the satellite record, gives 5.31 million km^2, which is close to a figure seen in recent years (5.36 in 2009), but well above any of our estimates or the 4.9 seen last year.

Below the fold for a few more words about our 3 estimates:

Read more »

How large a conspiracy?

Did you know that the observed decline in Arctic sea ice cover is all just a fake?  I didn't, but encountered folks who thought so.  Since I'm one of the people who would have to be involved in the conspiracy or at least being duped by the masterminds, I'll take a minute to ponder the matter and how someone who does not personally know many of the people involved could go about deciding whether there was indeed such a conspiracy.

One of the tools I find useful in considering issues is to follow a common mathematician's approach -- called the reductio ad absurdum.  That means reduction to absurdity.  What you do is assume the thing at hand to be true, and then pursue it logically to see where you go -- whether it leads you to absurdity.  This is also the starting point for a proof by contradiction.  Again, assume the thing to be true and see if it leads logically to a conclusion that contradicts what you know to be true.

So let's assume that there is indeed a fake involved in the decline in Arctic sea ice.  The people involved were a little particular -- the passive microwave sea ice record.

Some questions to pursue, then:

• How long would the conspiracy have to have lasted?
• How much data would have to be faked?
• Who all would have to be involved in the fakery?
• Are there other sources of data to confirm or refute the passive microwave observations?

Read more »

Happy Anniversary ...

 ... to me and my wife.  Part of the recent hiatus is due to me taking some time off to celebrate my 5th wedding anniversary with my wife.  I've marked this as a 'being a scientist' post since being a spouse is another thing that scientists do.  I enjoy that, and others of my roles -- being a son, father, uncle, brother.  Science is another, of course, and I enjoy that too, and is the point of the blog.  But a secondary point is that scientists are people.

We took the time, among other things, to think about what we have done in the 5 years so far -- good ideas we've carried out, storms we've weathered, and so forth.  And to think about what kinds of things we might like to try in the next 5.  There's a bit of science there -- experiments.  We try things, and some we like and keep doing, and some we don't, and quit.  Probably none of these experiments are publishable, but that's not the point.  We learn what we're trying to learn.  And have a lot of fun along the way!