sunny starry skies

Good summaries G-W and Michael Hauber. And any link to Jackone's data reviews is also worth a read! My briefest take on the year would be... Late season temporary freeze-up briefly takes Arctic ice near "normal", with a late maximum ice extent date of 31st Mar. Remarkably rapid melt between April and late June with Arctic dipole conditions (favourable for melt) takes us from above most/all recent years in IJIS data to the lowest recorded June extents. Late June to early July - poor melt conditions, Arctic dominated by low pressure sees remarkably low melts during July, and so 2010 lifted above 2007, but remained mostly just in 2nd place through July. Ice spread out across the basin with no coherent Beaufort Gyre, but looks thin on MODIS imagery with areas of open water/very loose pack opening up almost anywhere in the pack away from the Canadian Archipelago. Late July to present: mixed weather conditions, some dipole and some low pressure periods, with some sign of the Beaufort Gyre restarting. Melt has continued to be steadily above average, but not record-setting, and 2010 moved above 2008, but has remained more-or-less steadfastly below 2009 in IJIS data. Now looking very unlikely that 2010 will finish above 2009 or below 2008. That would place 2010 on the long-term accelerating decline for September extents (where 1996 is anomalously high and 2007 is anomalously low). Some further losses from the rapidly shrinking Archipelago ice shelves, a remarkably big berg calved from Petermann Glacier, and two large chunks lost from Jakobshavn Isbrae. Arctic sea ice looks thinner/more dispersed than in previous years on MODIS imagery (my non-quantified observation). That's all based on IJIS data, CT images and MODIS images, as they are the ones I follow most regularly. The geological argument is somewhat depressing - yes, the planet has been hotter in the geological past, and yes humanity is a blink in species history, but surely we should care about maintaining our species while we're here? After all we do have a vested interest in not wrecking our ways of life (agriculture, coastal cities etc). But that is OT! The Ice Age Now article was garbage - clue in the website title? The article was based on no data whatsoever, pure speculation.

Interesting - I was wondering if export through the Fram in September would delay the minimum extent date by offsetting the beginning of refreeze, and thus increase overall losses. It's only really relevant for September when loss/gain is in the balance. If '08 and '09 had little Fram export then when refreeze started, the balance can quite quickly become positive. The ice flowing freely through the archipelago is also nothing I've seen before for any extended period. It began in September last year, just before the refreeze, but the refreeze caught up with it a couple of weeks later and the floes solidified in place, before many made it into the NWP. The same will prob happen again, but this year much more ice has been able to push through and melt out - yet more old ice floes lost.

Most misconceptions like these can be found among the long list of skeptic arguments at Skeptical Science. I've listed them below with links to useful articles for you to read mycroft. http://www.skepticalscience.com/argument.php IPCC: ever tried to produce a document with as few errors as AR4? http://www.skepticalscience.com/IPCC-Himalayan-glacier-2035-prediction.htm Tropospheric hotspot: http://www.skepticalscience.com/tropospheric-hot-spot.htm - or more up-to-date here: http://www.realclimate.org/index.php/archives/2010/08/the-key-to-the-secrets-of-the-troposphere/ - the key point being that the hot spot occurs under any warming, not just GHGs. 'Cool years': aerosols: http://www.skepticalscience.com/global-cooling-mid-20th-century-intermediate.htm 'post-1960 trees': http://www.skepticalscience.com/Tree-ring-proxies-divergence-problem.htm - Only some trees (high northern latitudes) and only post-1960. Other trees (lower latitudes etc) don't have the problem, neither do other proxies. Matching centuries worth of non-divergence-related proxies with centuries of divergence-related trees identifies this issue as a uniquely recent phenomenon. Greenland/Antarctica are observed to be losing mass: http://www.skepticalscience.com/melting-ice-global-warming.htm None of these are really news though!

Much like a single extreme event not being indicative by itself of change, an increasing trend of extreme events (such as the well-known temperature charts for the US) is much more persuasive. In a similar way, right across the globe, we see responses consistent with AGW - one of those responses on their own are not indicative, but all together they provide a much stronger body of evidence, especially when taken alongside the direct measurements of increased radiative forcing due to CO2 molecules. Jethro, in your Dolomites soldier example, increased snowfall in that region after he died would have the same effect as lowering temperatures.

Update to the IJIS extent projections graph: Each red triangle represents 2010's minimum if extent loss from previous years is tagged onto the current figure. It's improbable that we will have an extent above 5250000, or below 4900000. On average, we have historically lost about 440000sq km from now to the end of the melt season. cooling climate, I wish I had your optimism, but this year looks near-certain to be between 2008 and 2009, and another data point right on the accelerating decline of the past 30 years. Does anyone know how strong the export out of the Fram Strait was in September of the past few years. I was wondering if that is any guide to the date of the end of the season? Namely that I think 2007 had strong Fram loss through September, and had the latest end date on record. 2008 and 2009 were early, but did they have much loss through Fram? May be completely wrong, but could be interesting as have increasing activity in the Fram Strait?

Not really, as you then have to show what natural cycle(s) drove such a past change. There is no evidence for natural cycles that can force present climate and past climate in the observed pattern... unless you are arguing that somehow the natural cycles operated in a different way in the past?? [or suggest that half a dozen different proxy types are all wrong in the same direction of wrongness]. You cannot base any hypothesis, or course of action, on an unknown that might be imaginarily the case - you have to show why it is the case. And present a compelling suite of evidence that not only shows your unknown process is consistent with the observed and proxy data, but shows why we can largely disregard CO2 variations which, coincidentally, already explain the observed and proxy data variations. So far, climate skeptics have failed this crucial test. An while the match between temperature and CO2 over the past 1000 years is quite appealing if the 'swiss horn' is closest to the mark, it does not provide direct evidence for a human imprint on climate. Direct evidence of temperature forcing includes outgoing and downward longwave radiation measurements showing the CO2 signature, and observations of increasing nighttime and winter temperatures, stratospheric cooling etc that show a signature in the forcing pattern of the atmosphere that is neatly consistent with GHGs, but not consistent with other forcings. They, to me, are the most important pieces of evidence. 'Swiss horns' tell us about sensitivity, and indicate a lower sensitivity to forcing than otherwise.

doctormog, the whole point of the graphs is to show that even the progressive extent decline may be conservative. The two extrapolations are clearly not consistent with each other, but we cannot be sure whether volume reductions will slow (or have been underestimated, data coming soon), or if extent reductions will continue to accelerate as ice gets critically thin. I'm sure you can grasp the concept that thinning a layer of ice will show little change in area/extent... until it disappears entirely. Not quite the same processes operating here, but it's quite possible that extent is fooling us into thinking we have longer to go before losing September ice. As for 'premature extrapolation'... Where does the current PIOMAS anomaly put us? Actually, lets assume the PIOMAS 'recovery' continues and accelerates next month and we have an anomaly of 'just' -8... and we still remain below the accelerating 1979-2009 trendline. So talk of recovery, or 'premature extrapolation' is, well, premature. I'll repeat the caveat from before, in case you missed it - if the PIOMAS data is wrong, these inferences are wrong. NNW, sorry to hear that you don't trust the science anymore. But where do you get the idea that the science is resisting even being tested? Did it occur to you that the people suggesting that the science isn't allowing itself to be tested are not doing good enough quality science to make a meaningful contribution? That these people then have an axe to grind, so suggest that they are somehow 'shut out', when the cold reality is that their actual science is garbage? As Dev says, it's not a case of whether or not we are influencing the climate, it's a case of 'by how much', and it's also a case of 'by how much' within boundaries constrained by ample data, such that 'how much' no longer includes 'not much at all'.

So one study equals the general scientific viewpoint does it? I thought the general research view on the Arctic was several more decades of decline before hitting zero at minimum ice? However... Maslowski may yet be not far off the mark if PIOMAS is right with ice volumes... But however you look at it, the trend is unfortunately downwards, and there's no real reason to suspect a reversal of that decline. There's a nice takedown of the 'recovery' illusion here: http://www.skeptical..._Just_Fine.html

http://www.ncdc.noaa.../?report=global http://data.giss.nas...stemp/2010july/ 2010 is the hottest year Jan-July on record, and we've just had the hottest 12 month period on record. I think G-W's statement of "the hottest period measured so far?" has some support in global records.

I'll call such reconstructions 'Swiss Horns' from now on, shall I?

stewfox - are you getting your dates confused in some points ? We're below 2009 at present, and only just above 2008 - so a minimum betwen 2008 and 2009 is not only likely, it would take remarkable conditions in either direction to take us outside those two minima. See the chart I posted the other day. Admittedly that's only based on the last 7 years of data and not the last 50 days so I could be confused . But the last 50 days takes us on exactly that trajectory, into 3rd place on the all-time low list. The quadratic trend (the best fit for the data) in declining September extents takes us below 2008 or 2007 within the next few years, presumably in the next year where weather conditions even remotely resemble 2007.

Jethro, those are exactly the two points I've been making all along. Thankyou. I'm happy not to discuss with YS anymore, as the concept of a rational discussion seems to disappear when the words 'hockey stick' appear in relation to research. It's not even that important in connecting humans to climate change - other lines of evidence are far more important (radiation measurements, changing patterns of temperature etc).

Funny how you keep saying the hockey stick is dead, yet it appears in numerous different proxies and numerous different reconstructions. Far from being dead, it's actually one of the most validated graphs in science. It does not just refer to tree rings (as you seem so obsessed by), but to a multitude of other proxies from flowering dates to borehole temperatures, via glaciers on the way. Quite what is 'cherry picking' about finding mutually consistent evidence from a great diversity of sources, while there is no scientifically valid evidence to suggest otherwise? http://www.skepticalscience.com/broken-hockey-stick.htm On Wegman among other things - it is well worth slandering as I would not use it even as toilet paper: http://www.desmogblog.com/crescendo-climategate-cacophony http://deepclimate.org/2010/04/22/wegman-and-saids-social-network-sources-more-dubious-scholarship/ [and links within] As for the NAS report which you persist in suggesating that it wrecked Mann's early hockey stick, maybe you should read the report and the discussion here: http://www.realclimate.org/index.php/archives/2006/06/national-academies-synthesis-report/ From the NAS summary: "The basic conclusion of Mann et al. (1998, 1999) was that the late 20th century warmth in the Northern Hemisphere was unprecedented during at least the last 1,000 years. This conclusion has subsequently been supported by an array of evidence that includes both additional large-scale surface temperature reconstructions and pronounced changes in a variety of local proxy indicators, such as melting on ice caps and the retreat of glaciers around the world, which in many cases appear to be unprecedented during at least the last 2,000 years. Not all individual proxy records indicate that the recent warmth is unprecedented, although a larger fraction of geographically diverse sites experienced exceptional warmth during the late 20th century than during any other extended period from A.D. 900 onward." Hardly demolishing the paper, is it? http://www.nap.edu/catalog.php?record_id=11676 Climate science moved on, past Mann et al (1998,1999), and confirmed the hockey stick. Only those people like MacIntyre and cronies (Montford, Monckton) still claim it's "broken", failing to realise there are many sticks made of different materials. The hockey stick is dead... in the eyes of a very few.

I linked to discussions with plenty of very serious criticisms of the M&W paper. Y.S., instead of insulting me for my views, why don't you head over to Deep Climate and see if you can come up with reasons why those criticisms are invalid, ditto for the criticisms at RealClimate. There's no point in having a debate with you here as all you do is throw insults when anybody suggests that MacIntyre might be wrong, Wegman might be a politicised and plagiarised report, or that the latest paper purporting to raise doubts about anthropogenic global warming turns out to have a number of critical flaws. When was the last time you were truly sceptical of claims made by MacIntyre, Spencer or that ilk? I'm sceptical of every scientific claim I see, whatever side of the fence it's from - some of those claims stand up to scrutiny, others don't. And I'll consider a claim rubbish if it is not supported by evidence. M&W's claims about reconstructive ability appears not to be supported by evidence. http://deepclimate.org/2010/08/19/mcshane-and-wyner-2010/ Though I do think M&W's statement is rather funny, for a skeptic paper: "Using our model, we calculate that there is a 36% posterior probability that 1998 was the warmest year over the past thousand. If we consider rolling decades, 1997-2006 is the warmest on record; our model gives an 80% chance that it was the warmest in the past thousand years." I just don't think the stats they did look likely to stand up to scrutiny, and their background reading falls very flat.

It's a bit rich to talk about ocean 'cooling' on the downward limb from one of the highest peaks in ocean heat on record. A look at the trend shows steadily increasing heat content in the oceans: http://www.skepticalscience.com/Robust-warming-of-the-global-upper-ocean.html http://www.skepticalscience.com/global-cooling-intermediate.htm But you're not really interested in trends, are you, Y.S.? You seem to prefer detrended measures such as AMO (detrended N Atlantic SST) or PDO (detrended and spatial measure of N Pacific SST), or an hypothesis that has repeatedly been shown not to work (negative cloud feedback).

Surely we've been here before - so far as I'm aware, 18 warm records in a single year is unprecedented, and a ratio of 18:1 is surely unprecedented. I'll be happy to see data that shows this not to be the case. I'm also happy to accept that the 19% land area is a bit of a red herring, when you have Russia and Palestine grouped together. But simply the number of national records provides an index suggesting that this year is remarkably warm. The year as a whole according to NCDC is on track to be the warmest on record, and as VP says, the calibrated measures such as CRU, GISS etc are more valuable than individual records. But a trend in regional or national records is simply a different measure of the warming - this time of the trend in extremes, rather than the trend in averages. Speaking of trends, it hasn't been cooling since 2000. A trip over to woodfortrees.org will sort that one out for those who are unsure. All trends since 2000, 1995, 1990, 1985 etc are positive. We have not departed from a rising linear trend starting in the late 1970s - while there is no reason to suggest we must stay rigidly on that rising trend, so far we have, and that includes the last decade. The last 12 monts have been the hottest 12 month period on record too.

I agree completely with that last post VP! The hard part is that it's very difficult to convince people that they are able to do something when they have convinced themselves they can't... It's a pity that the M&W paper fails so badly. It would have seemed to me an opportunity for statisticians to collaborate with relevant climate scientists and do the best possible job. Unless of course McShane and Wyner didn't want to come to the same conclusions as the climatologists... I find it amusing, in a way, that they can do such a poor job of reviewing the literature or understanding the methodology applied by Mann, Wahl and others, yet claim to overthrow a raft of independently verified climate reconstructions. And from what I can see, and from what others better qualified than me can see, they do an awful job of the actual statistics in the process. The only place they then get it published is of course a journal that clearly has no idea about why the paper is bad - which raises questions about how that particular journal is screening papers! And the only people who of course see it as flawless statistics perfectly applied to the topic are... Watts, MacIntyre and their acolytes, who will be horrendously critical of every piece of climate science , except something that happens to say what they believe, however bad a piece of science it is. Confirmation bias? Of course. Denial? Written all over their faces. When will they learn that to be truly sceptical you have to be sceptical of every piece of science, including the ones you initially think ought to be right?

The paper is certainly not a vindication of Wegman's plagiarised political rubbish, nor does it appear to be a successful vindication of McKitrcik or MacIntyre's so far failed attempts to discredit one of the many 'hockey sticks' in existence. The NAS (infinitely superior to the Wegman garbage) critcised Mann's statistics but vindicated his results. Others subsequently reproduced his results several times over with different methodologies, and Mann addressed the NAS criticisms in the 2008 paper. Those who think that McShane and Wyner have demonstrated anything more than the fact that statisticians really ought to consult with climate scientists before attempting to publish on climate science should read carefully the criticisms outlined at Deep Climate: http://deepclimate.o...and-wyner-2010/ "So there you have it. McShane and Wyner’s background exposition of the scientific history of the “hockey stick†relies excessively on “grey†literature and is replete with errors, some of which appear to be have been introduced through a misreading of secondary sources, without direct consultation of the cited sources. And the authors’ claims concerning the performance of “null†proxies are clearly contradicted by findings in two key studies cited at length, Mann et al 2008 and Ammann and Wahl 2007.These contradictions are not even mentioned, let alone explained, by the authors." [Deep Climate] I'm not qualified to comment on all the details of the statistical reconstructions, but I can comment that the choice of favoured review literature was awful to the point of being deliberately awful. It would not pass muster for an undergraduate essay. Lots of serious statistical issues raised by Deep Climate - anyone defending the paper in detail might have their work cut out it would appear. RealClimate also has a passing nod at it, with hints that there may be more to come: http://www.realclima...-it-yourselves/ I like Deltoid's take on it, here: http://scienceblogs....mcshane_and.php The most interesting part there is Martin Vermeer's early comment - one of the many errors in the paper is a failure to adjust for high latitude skewing of results - hence the slanting shaft of their hockey stick. But seeing as they purport to discredit palaeoclimate temperature reconstruction altogether, much more serious are the statistical failings pointed out at Deep Climate and RealClimate - it looks very much like this paper will be added to the list of those that fails to dislodge even one of the many hockey sticks on the rack from it's place. EDIT: Interesting second paper there VP - though it's 13 years old. Any sign of those problems being remedied? But the main issues with software such as those you pointed out are resolved by replication of results by different methodoloiges. In the case of 'Hockey sticks', tree rings, boreholes, lake sediments, glaciers, ice cores, corals and stalagmites all provide independent evidence, as do the reconstructions using different combinations of these sources and different methodologies. Computing issues then don't come into it IMHO.

Err, maybe better to look at the paper than my analysis based on Tamino's post! I used 'corrected' in that the measure was a method (average latitude of ice edge) which corrects for the fact that there are latitudes with relatively little ocean, notably around 66deg N. By contrast, the measures of ice extent or ice area are open to skewing at transitions across 'bottleneck' latitudes where as the freezing front moves south relatively little extra sea is available to freeze. The analysis is not process-based, so the relatively different processes in Arctic/Antarctic or whether it's extremely cold in interior Russia are not considered. The only consideration is the relative amount of sea available to feeeze at different latitudes. They have done this by using the average latitude of the ice edge as their measure. The paper's result is that the change in latitude polewards over the past few decades is consistent whether you are looking at March extent (where the average latitude crosses large land areas), or September extent (where the average latitude of the ice edge is mostly ocean). So if there was more ocean available, extents might increase, but that's not considering processes, as perhaps seasonality might increase without the protecting landmasses - a la Southern Ocean. Clearly when you consider processes, there are different issues and many potential complications, and I've no idea (and would doubt at first guess) if the same analysis of Antarctic sea ice would produce similar results. One complication is that the last bastion of Arctic ice is not the Pole, but a region around the edge of the Canadian Archipelago, so a poleward shift index will fail when the ice reaches very small extents. Another is that the freezing does not occur symmetrically around the pole, and freezing mostly occurs further south when close to continental landmasses (e.g. Hudson Bay). Hope that helps!

"average or less"? According to which metric? We're already below your 2006-scale minimum with ~3 weeks of extent loss to come. We've had a year with very little ice export through the Fram Strait during the summer, yet sea ice extent looks likely to be 3rd in the all-time low list. Given we've had very little loss through drift into warmer waters, loss has been in situ and volume losses, as confirmed by the latest PIOMAS estimate. I find it remarkable we are looking at one of the lowest extents on record without having very substantive wind-driven losses. My forecast based on IJIS data: The red triangles are projections based on adding extent changes for each previous year from today's date to their respective minima. 2006's remarkably low extent loss leads to the highest red triangle; 2008's rapid loss leads to the lowest red triangle; 2007's late finish leads to the lower-right triangle. You can also see that 2010 is roughly tracking 2008, and that 2008's season ended remarkably early. So the ballpark area for the minimum extent, unless we see something new for this year in terms of late-season extent loss (or extent maintenance) is approximately between 2009 and 2008, or the 3rd lowest on record. To see something outside these bounds we would have to observe something not seen in previous years of IJIS monitoring. An extent between 2008 and 2009 is essentially on track for an accelerating quadratic fit through minimum extent changes since 1979, particularly if late-season losses mimic 2007-2009, giving lie to the 'recovery'. sss

Very interesting charts VP - I did a similar reconstruction to yours witht he dataset I had, with a reference period 1870-1960, and testing it against changes after that. Using that reference period (rather than the whole 1870-2009 datset) gave 2007 as -8.7s.d. I didn't post that chart as it was almost "alarmist" (!), and I thought I should include recent years as a nod to those considering 'natural variability'. [My methods for the previous chart - take absolute sea ice extents from 1870-2009 (last few years extended based on NSIDC dataset correlation). Calculate mean 1870-2009, anomalies from that mean, and standard deviation of the anomalies. Using any shorter calibration period (e.g. 1870-1960 or whatever) leads to much larger standard deviations.] But clearly, whatever chart you use, the last few decades have taken the Arctic out of the position it has been in for the previous century and moved it into a new regime or path. It is not a 'natural variation' in a statistical sense. The mid-1970s has also been identified by Tamino in a recent post as a breakpoint in global temperatures. As one who is statistically-minded you'd be interested in that analysis: http://tamino.wordpr.../08/13/changes/ The physical explanation in terms of forcing tends to be aerosol reduction vs rising GHG outputs, whether any other processes gave an extra kick to make the corner a kink rather than a smooth bend I'm not so sure. Whatever processes operated have not then subsequently changed the slope of the graph. EDIT: A simpler explanation of the sea ice 'kink' is also the use of September minima, and perhaps partially explained below. Additionally, my dataset has suspicious values around the war/early postwar period which may turn a gradual change into a 'kink'. Another intriguing post at Tamino is a discussion of a new paper discuissing the possible causes of why September minima have reduced much more dramatically than March maxima in Arctic sea ice: The paper (abstract only unfortunately) is here: http://www.agu.org/p...0GL043741.shtml Eisenman 2010: Geographic muting of changes in the Arctic sea ice cover, GRL. Discussed at Tamino here: http://tamino.wordpr...e-with-a-twist/ It appears to be a quantitative analysis of the effect of the changing balance of land vs ocean at different latitudes. Current September minima occur where the mean latitude of the sea ice edge is almost entirely ocean, where the March maximum occurs at a latitude that is mostly land. When corrected for these factors, there is no statistically significant difference in the rate of poleward latitude movement of the mean ice edge throughout the year. September's retreat is moving polewards at the same rate as March's (both acelerating). It's a bit simplistic and I can think of a few potential significant quibbles, but it gives a fascinating new metric to assess sea ice changes.

After posting the last graph I realised it may be an error to consider the values for 2004-2009 as compared against the standard deviation calculated from 1870-2003. Below is the same graph, with standard deviations calulated from the anomalies between 1870 and 2009. This includes 2004-2009 in the variance estimate, increasing the variance. We see every year from 2002 onwards has a value more than 2 standard deviations below the mean:

VP, I am unaware of any evidence that shows that central pack to be fundamentally unstable before circa 1970. I did also say "mostly", to cover bases:whistling:, but it seems remarkably unlikely that melt has extended significantly into the central pack before the last couple of decades. I'm not sure where you think I've applied a liner least squares trend? You're right in that we need to highlight how far from the normal variance we are though (see below). Thanks for pointing out the reference period - I missed the obvious there! I've done (I think) something similar to what you were after, which is to extend the record of the NSIDC anomaly plot using the Kinnord et al 2008 data. It is anomalies for minima, rather than anomalies throughout the year (I could add maxima, but it takes a wee while to digitise the data), so in that sense it is not the same as the NSIDC plot. However, it does show how far out of the envelope of normal variance the last decade of minima has been: The 2007 and 2008 minima were >= 4 standard deviations below the mean, and all but three years since 1995 are >2 standard deviations below the mean. The best estimate for 2010 is ~3.5 standard deviation below the mean, or somewhere between the 2008 and 2009 values. Values for 2003-2009 are calibrated to the Kinnord scale based on the 1979-2003 correlation between Kinnord and NSIDC absolute extent values (r^2 of 0.92). It places our recent minima and the decline in minima in context - we are far outside what could be called "natural variation", or less than 2 standard deviations, in the icepack minima. Clearly the strength of this result is only as good as the input data - there are clear weaknesses regarding data during WWII, and the variance in pre-1900 data appears rather low. But there is a distinct departure from +/- 1 standard deviation beginning around 1975. EDIT: Error in the figure title - they are departures from the 1870-2003 mean.

Hi VP, I think the anomalies are departures from the mean for the whole period, 1953-2009. Might be worth setting it against the graph in the Polyak et al 2010 QSR review paper which goes back to 1880, though I think that is proxy data. That graph is a reproduction of one from Kinnard et al (2008), see below. Essentially, the chart (which is of extent) is consistent with a pack that had a large and mostly stable thick central pack with variations round the margins, and late 20th Century/early 21st Century melting that starts by thinning the pack, and in recent years has thinned the pack enough for extent losses to penetrate the central pack. The crucial issue is that a thin skin of broken up and mushed-up floes is quite different to a thick, stable pack with occasional leads - the latter description being consistent with all direct human observations and explorations of the pack before the 1980s. If you are considering departures from a stable 'mean', it may be worth looking up the following data, then you have a context going back to the end of the 19th Century. In that context, the recent extent losses are beyond 2 standard deviations I would think. Kinnard et al 2008, "Figure 2: Total maximum (green) and minimum (blue) ice extent time series for the period 1870–2003. Thick lines are robust spline functions to highlight low-frequency changes. Vertical dotted lines separate the three periods for which data sources changed fundamentally: (1) 1870–1952: observations of varying accuracy/availability; (2) 1953–1971: generally accurate hemispheric observations; (3) 1972–2003: satellite period - best accuracy and coverage." Kinnard, C., Zdanowicz, C.M., Koerner, R., Fisher, D.A., 2008. A changing Arctic seasonal ice zone – observations from 1870–2003 and possible oceanographic consequences. Geophysical Research Letters 35, L02507. The early pre-1953 data comes from Walsh and Chapman (2001): Walsh, J. E., and W. L. Chapman (2001), 20th-century sea-ice variations from observational data, Ann. Glaciol., 33, 444–448. The early data has been collected from various records and ship reports from DMI and Norwegian sources. I doubt there's a better collection of data for sea ice variations since 1880. EDIT: Note that the Kinnard data is only up to 2003 - nearly all of the last six years of minima would be below the bottom of that chart.

I would not expect any 100,000 melts at this time of year - there is only a single instance of a 100,000+ melt after this date in the IJIS record, on 24th Aug 2008. 2003-2010 extent losses after 20th Aug: 100K+melts: 1 90-100K melts: 1 80-90k melts: 3 70-80K melts: 4 60-70K melts: 9 As NDS alluded to, and borne out by IJIS figures, anything much over 60K is unusual at this time of year, and would be well above the average for this time of year. Between now and 8th Sept (end of 2008 melt season), average melts are between 30,000 and 47,000sq km for 2007-2009 seasons, though clearly with higher melts earlier in the period. Over the next week, we should expect an average melt rate of 40-50K at 2007 or 2009 rates, or >60K at 2008 rates. Jethro, you misinterpreted both what I said earlier and the articles you quoted. My point was that the see-saw "makes some gullible people think everything is OK", namely people who think Arctic ice loss is nothing to worry about. This does not include the scientific comunity, who have identified that there is a see-saw effect superimposed on a warming trend. What happens as the warming trend continues, even if the see-saw reverses? I would challenge you to show that the authors of the studies in question think there is "nothing to worry about" in the Arctic warming, and also refer you to the review I linked to earlier showing that the Arctic is in a state is has not been in for several thousand years. We're simply not seeing purely natural forcing of the Arctic. Pit: But much less than ever recorded outside the past few years... http://nsidc.org/sotc/images/mean_anomaly_1953-2009.png http://www2.sunysuffolk.edu/mandias/global_warming/global_warming_misinformation_sea_ice_increasing.html Or see the graph of sea ice since 1880 in the review of Arctic sea ice by Polyak et al 2010 (p1759).