Sunday, April 03, 2016


Eli and Jim Hunt (Great White Con) as mentioned here and there are engaged in a fun thing with the hard heads over at Bishop Hill.  OTOH Willard Tony protects his tiny flock by censoring Eli and many others,

Now there is all sorts of fanciful at both dens of denial, unicorns and such, but it occurred to Eli that there must at least be proxy records way back into the past for Arctic Sea Ice extent, and, indeed there is, from Reconstructed changes in Arctic sea ice over thepast 1,450 years by Christophe Kinnard, Christian M. Zdanowicz, David A. Fisher, Elisabeth Isaksson, Anne de Vernal  and Lonnie G. Thompson, Nature 479 (2011) 510.  It's open source so anybunny and their favorite hares can read it.

The top of the figure shows the multiproxy reconstruction of the sea ice extent going back a millenium and a half.  The blade pointing down (Willard Willard will explain that), is the decrease observed to 1995, As with all things this is not perfect.  For comparison, since the figure ends in 1995, the minimum sea ice extent in 2015 was 4.4  million sq km.
Our proxy-based reconstructed history of late-summer Arctic sea ice extent over the period AD 561–1995 is presented in Fig. 3a along with the observed sea ice record. The reconstruction and observational record were smoothed with a 40-year lowpass filter to highlight the best-resolved frequencies (Fig. 2b). The uncertainty range around the reconstruction widens notably before about AD 1600 as a result of reduced proxy availability and consequent decrease in reconstruction skill. Within this uncertainty range, this reconstruction suggests that the pronounced decline in summer Arctic sea ice cover that began in the late twentieth century is unprecedented in both magnitude and duration when compared with the range of variability of the previous roughly 1,450 years. The most prominent feature is the extremely low ice extent observed since the mid-1990s (T1 in Fig. 3), which is well below the range of natural variability inferred by the reconstruction. Before the industrial period, periods of extensive sea ice cover occurred between AD 1200 and 1450 and between AD 1800 and 1920. Intervals of sustained low extent of sea ice cover occurred before AD 1200, and may be coincident with the so-called Medieval Warm Optimum (roughly AD 800–1300) attested in numerous Northern Hemisphere proxy records18, but the pre-industrial minimum occurred before, at about AD 640 (T3 in Fig. 3). Two episodes of markedly reduced sea ice cover also occurred in the late sixteenth and early seventeenth centuries (T2 in Fig. 3). However, by the mid-1990s the observed decrease in sea ice cover had exceeded the lower 95% confidence limit of these prehistorical minima.


Great White Con said...

Thanks very much for the mention Eli.

I don't know about you, but Snow White has noticed that more of the usual suspects have been peddling misleading Arctic anomaly graphs recently. By way of example, the Global Warming Policy Forum have jumped on the Bishop's bandwagon, and thrown the PIOMAS Arctic sea ice volume anomaly into the mix for good measure:

More Of The Usual Hype About Arctic Sea Ice

The real life numbers do of course perfectly illustrate the GWPF's fairy story.

I don't know about you, but I'm heading back up onto The Hill to see if I can locate a missing comment of mine over there, or even a no doubt witty riposte to your currently visible one!

Great White Con said...

You just can't please some people, can you? They ask for hockey sticks and you supply them with a couple of fine examples, one of Arctic temperatures and another one of Arctic sea ice extent, and still they quibble.

One cannot help but wonder what the Bishop and his acolytes will make of the latest Arctic sea ice volume numbers. Pretty pictures of the March 2016 PIOMAS data are available hot off the virtual presses at:

Regional and gridded visualisations to follow in due course.

For some strange reason my erudite comment about the Northwest Passage is still conspicuous only by its absence. C'est la vie on The Hill I suppose?

Great White Con said...

The conversation seems to have fallen silent at The Bishop's, and here too for that matter! However things are getting much more animated over at Snow White's, where Kinnard et al. have just resurfaced:

Eli introduced some actual evidence into the debate

BBD said...
This comment has been removed by the author.
BBD said...

Great White Con

Your patience does you credit. There's no reasoning with RR, who, you will be reassured to know, also believes that ocean acidification is a lie cooked up by alarmists. Paranoid loon that he is.

cRR Kampen said...

I just remembered again why I put a c in front of my initials... (for cielo)

BBD said...

Ahem. Yes, perhaps that abbreviation was unwise, given where we are - not to mention your good self, cRR. I was of course referring to a commenter posting nonsense over at Great White Con.

Great White Con said...

Thanks for your kind words BBD. I like to think there's some method in my apparent madness, but your mileage may vary of course. Hunter has now popped in for tea with Snow White as well, and has posted some additional nonsense.

In the latest "Shock News!" from the Great White Con Ivory Towers, Bill the Frog has been "disappeared" from WUWT but nobody can work out why: