Comments on: Current Status of Arctic Sea Ice Extent

By: Greg Laden

Greg Laden — Thu, 24 Jul 2014 15:43:39 +0000

Right: I wanted two data sets from early vs. late.

This is the post where I originally used this approach in order to counter some rather idiotic claims being made about sea ice recovery:

http://scienceblogs.com/gregladen/2013/09/01/is-annual-arctic-sea-ice-on-decent-track-for-a-change/

By: Matthew Morse

Matthew Morse — Thu, 24 Jul 2014 15:36:29 +0000

There was a post on the NSIDC website last year when they changed the baseline. They changed it to match other climate baselines, even though it no longer starts from the start of the data.

Also, I misinterpreted your images when I first saw them to mean “the first ten years of the baseline” and “the second ten years of the baseline”. Looking again, it’s clear that you meant “one ten year set” and “another ten year set”.

So my first comment overstated the need for correction.

By: Greg Laden

Greg Laden — Wed, 23 Jul 2014 23:26:46 +0000

It is the first ten years of the data, and the last ten years of the baseline, which seems silly but the purpose is to no use the last few years so they can be broken out separately. . (I had noticed that I need to fix the chart)

By: Matthew Morse

Matthew Morse — Wed, 23 Jul 2014 23:02:59 +0000

Also, about a year ago, the baseline was changed from 1979-2000 to 1981-2010. Until recently, it was possible to display the older baseline on these graphs. It was substantially higher than the current baseline.

By: Matthew Morse

Matthew Morse — Wed, 23 Jul 2014 22:55:38 +0000

Some corrections: the baseline is 1981-2010, so your graph showing 1979-1988 is not the first ten years of the baseline. (Should be 1981-1990.)

Also, the baseline is 30 years, so you are showing (almost) the first third and the last third of the baseline period, not the first half and last half.

The conclusions remain the same, in any case.

Finally, it’s worth stating that all of the graphs come from http://nsidc.org/arcticseaicenews/charctic-interactive-sea-ice-graph/ where you can choose which set of years to view and zoom in on areas of interest, as well as viewing Antarctic sea ice extent (a new feature).

By: The Climate Change Debate Thread - Page 4279

The Climate Change Debate Thread - Page 4279 — Wed, 23 Jul 2014 17:47:38 +0000

[…] between the first 10 ears up to 1988, and the last 10 years: These are NSIDC figures, AFAIK. Current Status of Arctic Sea Ice Extent – Greg Laden's Blog Sign in or Register Now to […]

By: Arctic Ice: Midsummer Melt Update | Climate Denial Crock of the Week

Arctic Ice: Midsummer Melt Update | Climate Denial Crock of the Week — Wed, 23 Jul 2014 13:42:11 +0000

[…] Greg Laden’s Blog: […]

By: Greg Laden

Greg Laden — Wed, 23 Jul 2014 13:38:24 +0000

Michael. Yes, this is the period for which there is similar and good data.

I think these data have been analyzed all sorts of ways. It is common to smooth the curcpve with a moving average for climate data and I’ve done this with these data.

One question I have that is too early to answer but not to early to start playing with is this: at some point the decrease in surface ice minimum has to slow down, I assume above zero somwhere. At what point can we say that is happening? For several years the drop was virtually every year. Now it looks like it might be wiggling in place a bit.

By: Michael Kelsey

Michael Kelsey — Wed, 23 Jul 2014 05:01:33 +0000

A couple of questions (which you’ve probably answered elsewhere, of course). First, why does the data series start so recently, in 1981? Is that just when consistent satellite data became available?

Second, has anyone rebinned these plots in form of moving-window averages? Your second and third overlays are examples of this, and are pretty blatant demonstrations of statistical bias (in the sense of non-uniform scatter, or equivalently different underlying PDFs). I wonder if, for example, tracking five-year or ten-year moving averages would reveal a clearer trend than the year-by-year fluctuations.