From Science Daily where I read fairly often, I found this headline.
Sea Ice At Lowest Level In 800 Years Near Greenland
The title makes you instantly skeptical because sea ice isn’t at it’s lowest even in the last two years. Of course we then have to wonder how they determined sea ice levels back 800 years.
ScienceDaily (July 2, 2009) — New research, which reconstructs the extent of ice in the sea between Greenland and Svalbard from the 13th century to the present indicates that there has never been so little sea ice as there is now. The research results from the Niels Bohr Institute, among others, are published in the scientific journal, Climate Dynamics.
What do you know it’s another tree ring study in noise blending.
There are of course neither satellite images nor instrumental records of the climate all the way back to the 13th century, but nature has its own ‘archive’ of the climate in both ice cores and the annual growth rings of trees and we humans have made records of a great many things over the years – such as observations in the log books of ships and in harbour records. Piece all of the information together and you get a picture of how much sea ice there has been throughout time.
If someone has a copy of the PDF for this paper, I would appreciate it. In the meantime, I’ve copied the abstract below. It sounds straight from the team bendahockeystick playbook. The abstract can be found HERE
Abstract We reconstructed decadal to centennial variability of maximum sea ice extent in the Western Nordic Seas for A.D. 1200–1997 using a combination of a regional tree-ring chronology from the timberline area in Fennoscandia and δ18O from the Lomonosovfonna ice core in Svalbard. The reconstruction successfully explained 59% of the variance in sea ice extent based on the calibration period 1864–1997. The significance of the reconstruction statistics (reduction of error, coefficient of efficiency) is computed for the first time against a realistic noise background. The twentieth century sustained the lowest sea ice extent values since A.D. 1200: low sea ice extent also occurred before (mid-seventeenth and mid-eighteenth centuries, early fifteenth and late thirteenth centuries), but these periods were in no case as persistent as in the twentieth century. Largest sea ice extent values occurred from the seventeenth to the nineteenth centuries, during the Little Ice Age (LIA), with relatively smaller sea ice-covered area during the sixteenth century. Moderate sea ice extent occurred during thirteenth–fifteenth centuries. Reconstructed sea ice extent variability is dominated by decadal oscillations, frequently associated with decadal components of the North Atlantic Oscillation/Arctic Oscillation (NAO/AO), and multi-decadal lower frequency oscillations operating at ~50–120 year. Sea ice extent and NAO showed a non-stationary relationship during the observational period. The present low sea ice extent is unique over the last 800 years, and results from a decline started in late-nineteenth century after the LIA.
The effect of the calibration is almost certainly the same as the one demonstrated in this post:
https://noconsensus.wordpress.com/2009/06/23/histori-hockey-stick-pt-2/
The math of calibration creates a reduced amplitude historic signal in comparison to the calibration range almost guaranteeing an unprecidented whatever you’re looking for. The reason I’m confident is because they use uncalibrated tree ring data, combined with a partial calibration range to calculate their results. I’ve yet to see a calibration study which compensates for the temperature scale distorting effect of the noise on the data.
the Air Vent 
Jeff, some of the coauthors collect Finnish tree ring: Timonen, Eronen,… I covered some of the long Finnish tree ring series early this year and had very cordial correspondence with Timonen, who was grateful for the CA coverage. Moore and Grinsted are the authors of Rahmstorf’s smoothing method.
The claim of “”Significance of the reconstruction statistics”” by use of “”(reduction of error, coefficient of efficiency)”” is straight from the Team’s notebook. Also note that at 59% of the variance in sea ice in 133 years means that we have 6 total units in the 800 years. If errors propogate in a demonstrable way as Jeff has shown, using a log 2 decay means that the time when historical evidence indicates Greenland had much most ice, their method at best explains 35% of the variance (.59*.59 at 499 years from present). At the historical period that Greenland had the least ice, their method explains just over 22% at 1031 years from present. Not odds that I would be willing to bet the farm on.
Click to access Macias-Fauria_2009_ClimDyn.pdf
Thanks Steve and Roman,
I’ve already read through it one time. My first impression is that the verification statistics look superior to other papers but I’m still new to the whole thing.
We thus calibrated a multiple linear regression model on the period 1960–1997 that was verified against 1864–1939 data (e.g., Mann et al. 2005) http://www.meteo.psu.edu/~mann/shared/articles/MRWA-JClimate05.pdf
See Figure 2 of the Mannet al 2005. It is another hockey stick. Thus the appearence of the sea ice extant looking like an inverted hockey stick. It is. Inverse ice to temperature. They use the Mann for the verification period.
Am I reading Fig 2 a of Fauria et al 2009 correct? 1930’s or so has less SI than present, and it is the number of years that are low that are unprecedented? Considering their equation for SI=.33-.58TR-.27O, and using the Mann 05 hockey stick, Jeff based on your work, wouldn’t this mean that the past sea ice is likely deamplified, and their CI’s unlikely to express the variance correctly for this deamplification effect? Much less the magnitude of SI is wrong at the MWP?
How confident are we in measurement of sea ice in 1864, much less 1942?
Study says there has been considerable variability in sea ice extent but that the recent persistence of a period low sea ice in the Northern hemisphere appears to be unique.
Authors resist the notion that this is solely due to AGW (since the warming started at the end of the Little Ice Age) but do not exclude AGW contribution. They opine that cycles of NAO/AO and thermohaline circulation are most likely driving the changes in ice extent.
I find the results consistent with the “lukewarmist” world view that the continuing post-LIA warming may be marginally enhanced by human CO2 emissions but is not explained by or reducible to such emissions.
MIkeN It is not a measurement. It is a proxy estimation of sea ice that uses Mann’s tree ring 2005 proxies, I beleive.
Ah but you all miss the point.
How convenient to use 1200 A.D as the cut off point, at a time when the world was turning colder again and the Viking master mariners were already having to route southerly by stopping at Iceland.
Another hundred years back, 1100, and there was no ice. I am sure the proxies show that. And in 1100 the Vikings could sail direct winter and summer. With much shorter faster voyages and ample supplies of green vegetables in Greenland they had few problems, but by 1200 when the ice started to advance, and by then had come much further south, they had to go via Iceland, which no more than Greenland in the newer colder climate could hardly feed itself with greenstuff.
The well recorded written result of these longer voyages with no resupply of greenstuff from Greenland or Iceland produced scurvy on the return voyages, the first accurate written records we have of this disease.
So how convenient to select 1200 AD on the grounds of proxy data and not show the data which extend further back. And also how convenient that in 1200 temperatures had dropped more or less to todays and would fall still further in the next hundred years: but to ignore 1100 when temperatures were considerably higher than today.
Kindest Regards.
ay, there’s the climate rub,
For in that warping of data what dreams may come
When scientific integrity has shuffled off this mortal coil,
Must give us pause. There’s the disrespect
That makes calamity of so long a series of tree rings.
For who would bear the whips and scorns of Hansen,
Th’ oppressor’s wrong, the proud man’s contumely
The pangs of despised love, Waxman Markey’s law’s delay,
The insolence of office, and the spurns
That patient merit of th’ unworthy takes…
Have enjoyed the posts and comments as always.
Have a great Fourth of July, everyone!
Actually, the title makes me think that you don’t know how to spell “unprecedented”. But congratulations: Google says you’re number 2 of 45,000 users of that spelling.
Thanks, my not spel god.
This is what alerts my attention:
This paper by Fauria, Grinsted (yes!) et al, use (1) tree rings (we know about those, sensitive to CO2 and moisture as well as temp) and (2) ice cores. Quote from section 2 Data and Methods: The period covered by the ice core is A.D. 1200–1997.
Well, heck, the loose snow takes what, 70 years to settle down and compact into the permanent and truly impermeable ice, the process known as firnification. Now the ice experts Jaworowski and Segalstad were convinced that something was getting lost, either in the firnification of the snow, or in the methods used to retrive samples containing explosive clathrates – and that therefore, CO2 (at least) was reading too low. But why not 18O (temp) as well? Now for comparisons of ancient temp patterns, loss during firnification does not necessarily matter – but if you are taking a core sample that goes right through the firnification time, and Segalstad and Jaworowski are right, there will be a progressive skewing.
HAH!
There is another recent paper doing the same thing, and this is what alerted me. Jasper Kirkby – see http://wattsupwiththat.com/2009/07/01/message-in-the-cloud-for-warmists-the-end-is-near/ – uses the graph from Eichler et al 2009 – see http://www.eawag.ch/organisation/abteilungen/surf/publikationen/2009_eichler.pdf – to demonstrate the correlations between Sun, cosmic rays, and temperature, using 14C, 10Be, and 18O as proxies. But guess what, they also use ice core records that go right through the time of firnification, and that period (more or less) is the only time when the correlation progressively diverges. Or so it seems to me.
Now of course, Jaworowski is (in Team/”consensus” understanding) the lowest of the low. Perhaps because he shouted about this calibration problem, because of course, hey, that means that perhaps there is more to Beck’s measurements of fairly recent higher CO2 than meets the eye. Of particular note is the way in which Keeling Junior (who now runs Mauna Loa) wanted to silence Beck. That was what alerted me there. You don’t gag bad evidence. You let it speak and hang itself.
You may want to take a look at the original Lomonosovfonna ice core data. World Climate report has an entry on it here:
http://www.worldclimatereport.com/index.php/2006/12/08/a-stickier-handle-on-the-hockey-stick/
Note especially the pre-1200 and post-1200 data.