Arctic Sea Ice Reports: who to believe?

Anthony.
I really enjoy your website.
It has become a standard read of mine!
Thanks

Great catch. I’ve been talking with some colleagues about sea ice recently, and this apparent discrepancy is an important one. Thanks.

These folks homogenize temperatures all day long, why can’t they homogenize 15% ice extent? This is absurd, and if Anthony did not do such a careful explanation, appears calculated. I do note, though, the trend line still differs.

For me it’s a simple choice.
I am with Nanson Arctic Roos.
I don’t carry the concept of death spirals and I detest the the scaremongering tactics in support of power and money grabbing politicians.
There is nothing wrong with the climate or the Arctic, we won’t experience any dramatic effects in the rise of ocean levels.
The only thing we have to fear are the carbon scam artists that are after our money.
That’s it.

NSIDC has raised the bar, to make it easier for Serreze’s “death spiral” to limbo under.

All this suggests to me that the cycle is headed for the opposite end of the spectrum: Above normal ice pack conditions. The pendulum swings back.

What’s the problem here, they both clearly use a different baseline?
Nansen uses a 79-06 average and NSIDC uses a 79-00 average, that wholly explains the difference in their normal lines. Same measuring system + same “ice-covered” definition + different baseline == different normal value…
REPLY: Sure the baselines differ. I’m pointing out that the public presentations differ significantly and who defines “normal”? Normal seems to be in the eye of the beholder of the data. Essentially it is an anomaly, and you can make an anomaly look like anything you want with a simple choice of defining the baseline. – Anthony

De Rode WIllem (09:52:14) :
What a fuzz about nothing !!!! Both data gives about the same absolute amount of sea ice. The one gives just a normal amount and the other a almost ignorable shortage compared to normal.
I don’t see any reason to make noise about these data. Gosh….How low do we need to go to make a scene about something normal ?….If this normal situation is actually something whith a high news value….then there is something wrong ! If we stayed under normal vor the last 8 years, then it should be logical and normal to conclude something is terribly wrong with the Arctic sea ice content.

It shows how the artificially chosen baseline measurement affects the reported anomaly.
What is “normal” for the Arctic sea ice? We’ve only measured it by satellite for slightly over 30 years. How do we know what normal really is?

Does anyone know where the “Ice by Age” data comes from? I tried searching for the IceBridge data from NASA but apparently I am a little useless. I did find a great picture of a crack in the ice though, With an alarming proclaimation about open water in the NW Passage.
The images are visually making my BS detector going off and I would like to see the raw data and any algorithms used to create the graphics.
Since most are smarter than me around here anybody got this?

According to the NSIDC web page, “Fossil fuel burning is responsible for climate change”
Does this mean that “fossil fuel burning” has been going on for 4.5 billion years of continuous climate change on Earth?

There is nothinhg unusual, all of this happened before.
Read (a book from 1943):
http://www.archive.org/stream/arcticice00zubo#page/444/mode/2up

A bit off topic, but has anyone taken a look at the arctic death spiral propaganda being perpetrated by EDF?
“This is the story of a fictional polar bear family — Aakaga and her cubs Qannik and Siku — as they make their perilous journey in a melting Arctic world.”
http://www.edf.org/page.cfm?tagID=53590
This is hysterical!

paulo arruda (10:18:34) :
I have looked at that American Thinker article and believe the author has made a critical error. Concentration at the pole hole is much higher than 15% – actually closer to 100%. Using the correct concentration numbers, the NSIDC area and extent trends correlate correctly.

But if we assume that the pole hole is only 15% ice (the low end of what is assumed), then the downward trend is only 0.1% per decade, which is not statistically significant. (The corresponding downward trend for “extent” was 2.6% per decade.)

REPLY: I agree. Send me the results and I’ll send it to the American Thinker with a suggestion that they check their work and make a correction if indeed they made that error. -Anthony

The difference in direction in the recent trend (i.e., still increasing for NANSEN vs. decreasing for NSIDC – and the NSIDC revisions, documented here, for the last days of March) seems a bit incongruent, but the methodologies are somewhat different. Both eliminate any cells with less than 15% cover. NSIDC counts cells at >15% as all ice. NANSEN multiplies those same cells (that is if the cells are gridded the same) by the ice concentration within the cell (as I understand the description). So NSIDC should show a greater extent on any given day. I can’t tell from the graphs whether that is the case, but would be interested in that comparison if anybody wants to put out the effort. Regarding the difference in “Normal”, NSIDC is based on 1979 – 2000 while NANSEN is based on 1979 – 2006. So the lower NANSEN normal makes sense since extent in 2001 – 2006 was lower than in 1979 – 2000. But it’s interesting to see that we do seem to be returning to a more “normal” condition (as normal may be defined), at least for now. It will be interesting to watch the trend in the months to come as we go through the “Straits of June”, as on commenter recently coined.

De Rode Willem,
You have to understand what “normal” actually means in context. NSIDC uses a baseline period of 1979-2000 to calculate “normal”. NANSEN uses a baseline period of 1979-2006 to calculate “normal”.
What this means is that the NSIDC uses 1979 and the early 1980’s in their calculation of normal (all years with very HIGH ice cover), but does NOT use 2000-2006 (some of these years had very LOW ice cover). NANSEN, on the other hand, does include 2000-2006, so their calculation of “normal” is somewhat lower than the NSIDC number for “normal”.
In order to know what is truly normal (as in, what is a typical average ice-cover area for the arctic), we would probably have to have an absolute minimum of 100 years of data, and it would be far better to have, say, 10,000 years of data. That would give us a MUCH better idea of what is truly normal as opposed to some arbitrary “normal” based on a very small dataset.
Unfortunately, we did not begin getting satellite data for this until 1979, and 1979 and the early 1980s had very high ice-cover. In a 30-year database, 4 or 5 years of very high ice-cover is going to bias “normal” to the high side.
So, it is important to remember that “normal” has nothing to do with “the expected average” in this case. In this case “normal” simply means either the 21-year or 27-year average ice-cover in the arctic. Whether these 21 or 27-year averages resemble “normal” in any meaningful way is basically anyone’s guess untill we get a LOT more years of data.

I’m flipping out over this news! That increase is going to increase albedo during the summer months, and cause rapid cooling of the planet! We’ve reached a tipping point, and we’re going to plummet into a new Ice Age! And it’s all from ice formed from the gases released by mankind’s industrialization! AHHHHHHH!!!
*dons sackcloth*
And don’t accuse me of overreacting. The science is settled!
*sets hair on fire*

I’m still interested in seeing the actual raw data or pictures for the “maximum ever” Arctic ice extents. When you compare the “better instrument” in the 2002-now AMSR-E’s data to the average, the difference is a whole lot of ice. And half the data has to lie on the other side of the average.
The actual Arctic is still freezing pretty solid – the “missing” ice is precisely the same areas that (1) should be well documented by shipping reports, and (2) just inherently seems unlikely to freeze from a current perspective.

I don’t understand why they don’t use all years for the average. Isn’t that the way it is supposed to be calculated? We all know that we really don’t know what the “average” is supposed to be, since we have relatively limited data, but why not recalculate it every year? They do that with baseball statistics. A players’ season or career average changes every day, though the career average will barely change day to day, and even later in the season, his seasonal average will not change that much day to day.
But why would they not calculate recent years in order to figure out what “average” is? Is it because they assume the ice is not supposed to be low, therefore the last decade or so should not be counted? I would think every baseball player would love to have their bad years thrown out too!
Someone said Meier wants an unchaning reference, but averages do change over time, don’t they? Someone else could use the last 10 years as the average baseline, and we would see that ice is now WAY above average, and we must do something to stop it!

NSIDC does not have a rational explanation for the fixed average they use. I could speculate that they saw a decline and decided to fix a time range to reference to. Since we are seeing an increase your point is well taken. They should add each successive year into the average, much as they do when the perform their regression analysis.

Brian in Bellingham (10:57:38) :
http://nsidc.org/arcticseaicenews/faq.html#1979average
Why do you use the 1979–2000 average for comparisons?
NSIDC scientists use the 1979 to 2000 average because it provides a consistent baseline for year-to-year comparisons of sea ice extent. Scientists call this long-term average over a data series a “climatology.” If we were to recalculate the climatology every year to incorporate the most recent year of data, we couldn’t meaningfully compare between recent years. To borrow a common phrase, we would be comparing apples and oranges.
The problem with relying on a sliding average becomes clear over time, when we try to compare new years of data with previous years. For example, if we rely on a standard, unchanging climatology like 1979 to 2000, we can easily and clearly compare September 2007 and September 2008 with each other. However, if we were to use the sliding climatology of 1979 to 2006 for September 2007, and the sliding climatology of 1979 to 2007 for September 2008, we would no longer be comparing “apples to apples” when we compared the two years to climatology.
Finally, some scientists point out that since 2000, sea ice has declined precipitously. While you can do an average over any period, it is better to do so over a stable period, either a period of relatively flat change or cyclical change with little overall trend. If you include a strong increasing or decreasing trend when you calculate an average, you probably will not have a representative average.
That said, NSIDC has recently considered revisiting the 1979 to 2000 average. We now have thirty years of Arctic sea ice data. A thirty-year time series is a widely accepted scientific standard for a climatology because it is long enough to encompass most cyclical patterns of natural variation. The problem, however, is that we would have to deal with the potential confusion caused any time that a standard is changed. The graphs would look different to the general public and would require a great deal of explanation.
For those who are interested in comparing the thirty-year decline in Arctic sea ice extent to something different than the 1979 to 2000 average, the NOAA Arctic Report Card 2008: Sea Ice offers a graph showing groups of five-year averages from 1979 to 2008. What one immediately notices is that the overarching story remains the same: Arctic sea ice is rapidly declining over the satellite record, no matter how you calculate the averages.

I’ve been posting for yonks about this here, Blackboard and Mike Marinaralenas site… finally its being noticed. I believe it requires much more investigation ie icearcticgate. LOL. Once again DMI ice is live data
http://ocean.dmi.dk/arctic/icecover.uk.php with no suggestions/agendas
here is Mike’s records of ice re-adjusments for past 3 years
http://mikelm.blogspot.com/2007/09/left-image-was-downloaded-from.html
Arctic ice is much easier to fiddle with as each “slab” of ice lets call it can have different borders etc (eyes of beholder) old ice, new ice ect. No such thing in Antarctica so no fiddling there. Notice how SH has been in fact ABOVE anomaly for past 3-4 years! Even CT has been unable has been unable to play with that one. The AGW’ers cannot admit defeat on this one its far too important and would bring the edifice down much quicker than desired (until at least they can find new jobs for them). Another favorite (in this case) is to play with the average so current data always looks below (suspect who?). Anyway the whole thing is BS because its only 30 yrs data = meaningless so I dont care if it goes up or down it doesn’t mean AGW warming or Denier cooling haha

anthony:
Note that in the magnified view, NANSEN has a peak “normal” of ~15.25 million square kilometers while NSIDC’s “normal” is higher at ~15.75 million square kilometers. You’d think there would be a standard for deciding what is the “normal” baseline wouldn’t you? [Note: The NSIDC average is for 1979-2000, NANSEN’s is for 1979-2006] Maybe the scientists can hammer this out at the next ice conference.
you are right. the exclusion of 2003-2006 data from the NSIDC avg number alone will increase the peak number for the historical avg(???) by 0.2 million km2. excluding 2001-2002 ( for which i have no data to do the calc ) probably will add less than 0.1 million km2, could be 0.05 million km2. So, only about half of the difference ( between 15.25 and 15.75 ) is explained by the exclusion of years 2001-2006. the rest has to come from somewhere else. and as you said, they both can/may explain that 0.25 million km2 difference.

I’ve got the Arctic sea ice extent very close to the 1979 to 2010 average at only 27,000 km2 (0.2%) below average.
This comparison will not be perfect as some adjustment was required to match up the datasets but it gives a reasonable indication of where 2010 sits now compared to other years.
http://img517.imageshack.us/img517/529/nhsieapril7.png

“What Is Wrong With Science Today”
Googled on Cryosat 2, found this brief news piece.
With this picture (Caption: “Artist’s impression of CryoSat imaging an iceberg, image courtesy of EADS Astrium”).
*groan*

I do expect that NSIDC will go to a 30 yr baseline *eventually*, reclaiming their scientific self-respect. And it won’t be a sliding baseline (nor should it in my view), but it may or may not start in 1979.
I think they believe that the inexorable retreat of the arctic icecap will give them plenty of opportunity to switch to a 30 yr baseline a few years down the road, without creating that “confusion” they cite today, because the baseline line will still be comfortably above the reality at that time. It wouldn’t be today, no question.
What’s going to be embarrassing for them is if the arctic ice refuses to cooperate on that score over the next few years. Then they may be forced to take their scientific manhood in hand and bite the political bullet anyway eventually.
If 2010 ends up where I think it will, then perhaps they’ll consider using a 30 yr baseline ending at 2010. That might appeal to them because it will somewhat minimize the 2007/2008 dragdown effect.
If 2010 ends up where Anu and R. Gates think it will, perhaps that will give NSIDC the confidence to go to a 1979-2008 baseline, in the greater confidence that 2011 won’t cause that dreaded “confusion”. Tho I suspect they’ll want to wait until 2012 or so, even if retreat resumes below the 2007 line to be sure of not being embarrassed by “confusion”.

And all of this while CO2 has risen substantially…

Looking at the NANSEN unfiltered data in the graph, it appears to look more similar to the NSIDC. Anybody have a clearer picture of that?

Baselines being different don’t matter, nor does coverage area. The problem is that the actual numbers sometimes match and sometimes do not, sometimes by a million km2. Compare either the January start line of 2007 and 2010 extents or March 1 2007 and March 1 2010 extents. I can’t trust either source. Facts are verified data, this ain’t it.

Glad to see this. I was wondering why Nansen wasn’t reporting lately.
Using the 1979-2000 base seems OK as long as it is disclosed. That baseline does imply that those years were “normal” and later change is thus “abnormal.” But that is stretching. NSIDC shows what it shows and eventually will abandon their weak argument about the baseline.
Good to see another satellite launched today. I prefer several measuring the same ice but reporting through independent agencies.

Do they remove 2007, since it is an outlier?

Some have mentioned a ‘change’ in baseline may be appropriate. While that may be true (using a 30yr spread seems consistent with other climate methodologies) it may give a false impression of what is going on.
Particularly with the general public – they will see these numbers jump all over the place, demonstrating some kind of inconsistency – and will fall back on what they believe, rather than what they know.
I’m no fan of ‘hiding the decline’; unfortunately, going to a 30 year span will do precisely that (basically shifting your baseline down). This will force people to look at the historical picture, putting them into information overload, and, once again, putting people into belief mode. Since we have so few measurements, it’s really an arbitrary line, anyway, and used for political purposes.
I would favor forcing the hand of the AGW alarmists to shift to the (perhaps proper) 30 year span. True, as always, the AGW sceptics are still in the reactionary position, but it’s not always a bad thing to be there.
Summarily, use an ‘average’ which gives us the best guess of consistent cyclical coverage rather than the 30 year span. This doesn’t mean the average is ‘normal’, but just a span in time where the coverage did not vary as much as it has over the past decade, and gives a reasonable point of comparison. This is what the human eye naturally does, anyway.

KC (10:24:03) :
A bit off topic, but has anyone taken a look at the arctic death spiral propaganda being perpetrated by EDF?
“This is the story of a fictional polar bear family — Aakaga and her cubs Qannik and Siku — as they make their perilous journey in a melting Arctic world.”
http://www.edf.org/page.cfm?tagID=53590
This is hysterical!
I can’t recall the word for it at the moment which attributes human behavior and character to animals.
Using this technique I often find deplorable, particularly when aimed at children.
I watched David Attenborough documentaries when he (and others like him) demonstrated the brutality of life in the animal kingdom. Nowadays, such documentaries, although showing the exact same things from decades ago, always have that political ‘man did this’ undertone – or, more and more, blatant overtone.

@geo
NSIDC hopped on the AGW bandwagon and now can’t get off and still keep a straight face. Otherwise my guess is that they’d stopped with the screwy semantics in their FAQs a several years ago and hopped on the reality train.
——-
If NSIDC had had 150 years of data then sure jumping over a few years between 2001-2010 wouldn’t have mattered much and could’ve easily been rectified by a proper error bar. But now they have 21 years which they claim is a proper static long term normal…. suddenly those 30 years as a some kind of minimum went out the window.
A problem with their reasoning is of course that today isn’t 2001 but 2010. 2001, and maybe 2002, their arguments were sound, but now they have 10 years to their last entry for their 21 year normal. That’s an almost 50% difference in time length with the result as in comparing 2000 to a normal that was computed for the years 1850-1950, which only is ok if you have a proper context and reason for doing so.
NSIDC doesn’t try to describe reality, which could’ve been ok if they’d had a proper context to go with their stuff.
They now have a proper 30 year timeframe. And if they can take 1979 and compare it with a normal based on 1979-2000, then of course it’s equally ok to take 2009 and compare it with a normal based on 1979-2009.

DocattheAutopsy (12:32:53) :
FWIW, the posts on this website, and the subsequent discussions, are the reason I come here. It’s a wonderful little conclave of logic and reason, with intellectual arguments thrown in there. Thanks to all the scientists who continue to pursue the discourse of data and reason in a congenial environment.
—
REPLY: Thanks! Join in any time, this is a good bunch of folks!
Quick thought: consider how much computing speed and memory have improved over the time-spans involved in these time series graphics, as well as improvements in sensor technology. Perhaps we are now seeing a more accurate/comprehensive picture of Arctic and Antarctic ice extents?
Back in 2000, the Pentium VI was state-of-the-art, and Pentium III in widespread use.
One of the first rules of epidemiology (my field) is to first ascertain the accuracy of your data….are results real, or the result of better monitoring/diagnostics?
This is an ongoing discussion regarding autism spectrum disorders (is the increase in incidence real, or due to better diagnostics?)
Satellite systems are not my strong suit, any thoughts?

Phil M (13:16:09) :
All this talk about spin…it’s interesting that this figure never gets posted here:
http://nsidc.org/images/arcticseaicenews/20100406_Figure3.png
Enjoy your return to “normal”. Me and my eco-fascist-warmist-greenie-halfwit-tree-hugging-sandal-wearing-dope-smoking-scientist buddies would like to see you all hide THAT decline…
Thanks Phil, that’s 723.

Phil M
I would like to see that graph referenced to zero Km squared and then see how precipitous the resulting slope is. The total drop in that graph is only one million square kilometers, a number I don’t find very threatening.

“OceanTwo (13:26:29) :
[…]
I can’t recall the word for it at the moment which attributes human behavior and character to animals.”
Animals that look like and behave like humans: antropomorphic.
People that look like and behave like antropomorphic animals: Furrys.

I believe the UK Guardian Newspaper who had this headline based on a NSIDC source
“Arctic winter ice recovers slightly despite record year low, scientists say”
Phew, managed to get the “record low” in so presumably we are still on course for a death spiral.
Link is
http://www.guardian.co.uk/environment/2010/apr/07/arctic-sea-ice-recovers-slightly

Is it just me, or for the last week NANSEN shows ice still increasing, while NSIDC shows decreasing? Opposite trends?
For the downward trending NSIDC plot, can anyone check to see what the numerical difference is to normal for the last week? Checking numbers might reveal some ‘fixing’ of data.

Maybe we should believe that there is a lot of error involved in trying to figure out how much ice cover there is.

“…Walt Meyer has explained their choice to stop at 2000 many times (they want an unchanging reference)…”
Since somebody referenced the unchanging reference period used by GISS (totally ignoring the WMO’s guideline of using a minimum 30 year period ending at the decade), I won’t mention it again.
Oh, wait…
Has anybody ever put up a spaghetti graph of all the years? They only seem to chose the “lowest” values in their chart. Would love to see ALL the years that fell below their “normal” line.
For them to have “error bars”, there would have had to been a FEW years that went below (or do they only want to show the “record” low values).

CRS, Dr.P.H. (13:56:10) :
[…] Back in 2000, the Pentium VI was state-of-the-art, and Pentium III in widespread use.
Excellent point!
And considering the great lag between satellite system conception – design and deployment as chips are custom built, I bet most satellites in service today are still on the 386 or maybe 486 level, if that. OTOH, being realistic, even 1900 vintage thermometers, when built and tested by true scientists who cared for accuracy, were extremely accurate, in fact, in many ways they had better absolute accuracy than most modern electronic models when read properly. Electronics tend to drift with age, temperature, and even background cosmic ray noise levels that cannot ever be totally compensated for; even the compensation circuitry falls prey to the same said effects. In some respects we have taken a step backwards in respect to absolute accuracy, don’t you see that sometimes too? You get more coverage with satellites and usually more precision but give up absolute accuracy.

So let me see if I get this right. These bozos can’t even measure the amount of ice in the Arctic region today despite the billions of public dollars spent on satellites and study after study and they want me to believe they have any clue how much ice was there a couple hundred years ago? And still these “climate scientists” insist that 1) the world is headed for doom unless we all drive electric cars and cut down on toilet paper use and 2) if we just give them billions more they can really, really prove it this time?
Bernie Madoff is a piker compared to these guys.

geo (11:57:46) :
I do expect that NSIDC will go to a 30 yr baseline *eventually*, reclaiming their scientific self-respect. And it won’t be a sliding baseline (nor should it in my view), but it may or may not start in 1979.
I think they believe that the inexorable retreat of the arctic icecap will give them plenty of opportunity to switch to a 30 yr baseline a few years down the road, without creating that “confusion” they cite today, because the baseline line will still be comfortably above the reality at that time. It wouldn’t be today, no question.
It’s true that baselines that include 1979-2008 would be lower than a baseline of 1979-2000, because the Arctic ice is declining, decade after decade.
But that doesn’t mean the even now we aren’t lower than that 30 year, lower baseline:
http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/seaice.recent.arctic.png
http://arctic.atmos.uiuc.edu/cryosphere/IMAGES/sea.ice.anomaly.timeseries.jpg
Any way you slice it, the Arctic is losing ice, decade after decade. For as long as they could measure all of it. If you pick a baseline of 2002 to 2009, you might still get a few days above baseline… but that won’t stop the Death Spiral down to no ice that will come soon enough.

NANSEN says:
“Ice extent is the cumulative area of all polar grid cells of the Northern Hemisphere that have at least 15% sea ice concentration…
***************
NSIDC says:
“Extent defines a region as “ice-covered” or “not ice-covered.” For each satellite data cell, the cell is said to either have ice or to have no ice, based on a threshold. The most common threshold (and the one NSIDC uses) is 15 percent, meaning that if the data cell has greater than 15 percent ice concentration, the cell is considered ice covered; less than that and it is said to be ice free.”
The way I read that is for NANSEN is >=15% While NSIDC is >15%
It might not make a hill of beans difference, but it caught my eye.

I certainly would if he said he *wanted* to use a 30 yr baseline but didn’t dare because of fear of “confusion”.
And I’d support him doing so, even if his reasons have nothing to do with politics.

I lined up the 2010 NANSEN & NSIDC plots. Watch the blue line:
http://i40.tinypic.com/vnmhoo.gif

This is a case of comparing apples to oranges:
Using this set of data:
N_03_area.txt
at this address:
ftp://sidads.colorado.edu/DATASETS/NOAA/G02135/Mar/
Which has a headline of:
FTP directory /DATASETS/NOAA/G02135/Mar/ at sidads.colorado.edu
I plotted out this graph:
http://www.robertb.darkhorizons.org/TempGr/MarExtentVSArea.JPG
Where the Sea Ice is displayed as
N. Hem. Extent (plunging … the graph we normally see and cited often)
N. Hem Area (flat)
Global Extent /2 (flat)
Global Area /2 (somewhat rising)
S. Hem Extent (rising)
S. Hem Area (rising)
All baselines are computed the same, 1979-2010 inclusive.
If we combine N. Hem extent with S. Hem extent the result is flat.
If we combine N. Hem area with S. Hem. area the result is almost flat (which isn’t saying much other that it’s statistically insignificant).
The dwelling on N. Hem. Extent while ignoring the counterpart in the S. Hem. is disingenious and highly misleading.
If this wasn’t costing the taxpayer unnecessary burden and thowing good money after bad, it would be a joke.
Whom to believe??
I’ll believe the data straight up, on the rocks. ALL of it.

What is the cause of the tiny rebound in June every year on the JAXA Arctice Ice extent graph?

1DandyTroll (16:29:08) :
CRS, Dr.P.H.
‘Quick thought: consider how much computing speed and memory have improved over the time-spans involved in these time series graphics, as well as improvements in sensor technology. Perhaps we are now seeing a more accurate/comprehensive picture of Arctic and Antarctic ice extents?
Back in 2000, the Pentium VI was state-of-the-art, and Pentium III in widespread use.’
Actually it has never had much to do with the hardware. As an example, i386 CPU’s are still in use by NASA. No matter the hardware, crappy software will still be crappy software. Why do you think mission critical hardware has had to prove it self over time? And in space over time against radiation.
–
‘This is an ongoing discussion regarding autism spectrum disorders (is the increase in incidence real, or due to better diagnostics?)’
Is the incidence level real or just perceived?
First and foremost the autism spectra has gone from narrow to become somewhat braodbandish.
Second, peoples’ diagnoses are usually a function of money, either by individual or by society, or both. As in the more people who can afford a diagnosis of autism the more people with autism will live in that society, or reversed the more a society can afford to give the diagnoses…. In Europe this is actually becoming a serious problem, so much so that neighbors get different diagnosis’ for the same autistic ailment just because there’s a virtual line going through the neighborhood, some doctors in some cities, depending only on the city “treasury”, don’t give diagnosis of autism to people over a certain age, and I’m not meaning just 65, or retirement, but rather 25.
I’ve a brother and an uncle who’s autistic to various degrees, if you wondered.
—–
REPLY: Good point on the processors! I was told that the i486 processor was the beginning of the end for the Cray supercomputer, so you have a great point on software. I still have a Pentium 3 that I fire up on occasion, it works well through the Internet via ethernet.
OT….regarding autism, there is much discussion amongst epidemiologists about this. The general opinion is that the increased incidence is real, eg. not only due to better diagnostics and recognition. I have many good friends with children afflicted with Asperger’s and related autistic spectrum disorder.
Why? Not the vaccines, they have been vindicated. I’m reviewing the fairly recent rise in consumption of sushi by pregnant women as a major risk factor….tuna is filthy with organic mercury! I never touch the stuff anymore.
One reason why the AGW stuff ticks me off, we have much more important things to work on and spend time with than these myths and legends. Sorry to wander OT, guys!

Any way you slice it, the Arctic is losing ice, decade after decade. For as long as they could measure all of it. If you pick a baseline of 2002 to 2009, you might still get a few days above baseline… but that won’t stop the Death Spiral down to no ice that will come soon enough.

This statement makes it sound as though the Arctic Ice has been stable at high numbers for all of history and is just now losing ice. The assumption and this statement is absurd. Satelite record is so incredibly short that the only meaningful information that can be garnered is that the ice has declined for the last 30 years. Even if we only go back for 1000 years of climate history (in which we experienced both warm and cool periods) the only scientific thing you could say is that the ice has declined for the 3% of the last 1000 years thats we have accurate records for – and that is nothing compared to the time period of this interglacial.
Arctic Ice decline, as we see it, cannot be attributed to AGW just because the tiny slice we see has been declining. That is attempting to prove the theory because of correlation – and that is bad road to go down. The reason sceptics jump on the increase, is because while the decrease has correlated with AGW to date, a diversion will be hard to explain within the theory. In addition, most sceptics are sick to death of overblown reactions to what we are seeing – such as the “death spiral” and then attributing that to climate change. We have not seen catastrophic climate change. There is not even any evidence that we will see catastrophic climate change. It is also infinitely more likely that if we do see catastrophic climate change it will be us freezing our collective asses off and wishing for the days of “global warming” because the history of this planet shows that almost every catastrophic climate change in history was not hot – it was cold. They don’t call our current time in history an interglacial on a whim.

Close enough for guv’mnt work.

Richard Sharpe (17:02:04) :
So, that’s your prediction, is it? Does it matter to you that there is evidence that the arctic has been ice free in summer during the last 20,000 years?
There’s “evidence” that JFK was shot by three people, if you use the term loosely.
The hard part is proving it.
How about starting with a citation or two ?

R. de Haan (17:53:51) :
Fair is fair. They (alarmists) are getting big bucks for stirring up nightmares and stressing out millions.
That’s it. We should immediately open a clinic for people seeking relief from AGW induced post-traumatic stress disorder.

Phil. (16:23:51) :
geo (11:57:46) :
I do expect that NSIDC will go to a 30 yr baseline *eventually*, reclaiming their scientific self-respect. And it won’t be a sliding baseline (nor should it in my view), but it may or may not start in 1979.
Interesting, do you think that Roy Spencer’s use of 1979-1998 as his baseline undermines his ’scientific self respect’?
Dr. Spencer still has all the scientific self respect he started with.
Read all about it in his book:
“Climate Confusion: How Global Warming Hysteria Leads to Bad Science, Pandering Politicians and Misguided Policies that Hurt the Poor”
http://www.drroyspencer.com/climate-confusion/
T-shirts, mugs and hats also available.
Donations accepted for his website – he takes VISA, Mastercard, AMEX, Discovery and Paypal.
http://irregulartimes.com/wp-content/uploads/2009/02/dr-roy-spencer.jpg

PeterB in Indianapolis (10:35:52) :
“….and it would be far better to have, say, 10,000 years of data.”

From NGU – 20 October 2008
“Recent mapping of a number of raised beach ridges on the north coast of Greenland suggests that the ice cover in the Arctic Ocean was greatly reduced some 6000-7000 years ago. The Arctic Ocean may have been periodically ice free.”
http://www.ngu.no/en-gb/Aktuelt/2008/Less-ice-in-the-Arctic-Ocean-6000-7000-years-ago/
Nothing to see here folks, move along, move along.

Jimbo (20:48:14) :
From NGU – 20 October 2008
“Recent mapping of a number of raised beach ridges on the north coast of Greenland suggests that the ice cover in the Arctic Ocean was greatly reduced some 6000-7000 years ago. The Arctic Ocean may have been periodically ice free.”
http://www.ngu.no/en-gb/Aktuelt/2008/Less-ice-in-the-Arctic-Ocean-6000-7000-years-ago/
Nothing to see here folks, move along, move along.
What’s your point ?
That maybe the Sun had a few decades of unusual brightness 6000-7000 years ago, and the Arctic ice melted for awhile ?
That this might happen again this century, when we already have CO2 warming the planet, so a freakish Sun brightening would be twice as dangerous ?
Maybe it was a huge volcanic explosion that sprinkled ash all over the Arctic, and this absorbed the sunlight that summer leading to an Arctic sea ice Death Spiral ?
Any point at all ?
Maybe it was the Sumerian gods – they were pretty active about 7000 to 6000 years ago…
I’ll wait till this “beach ridge” finding generates some concrete hypotheses as to why that small region of the Arctic was ice-free before I worry about whatever caused it adding to the current global warming.

@David Williams (17:31:22) :
Actualy, if you do the math, then if you accurately grab the right 30 years 1/2 cycle of a a 60 year cycle, it does in fact work.
You can argue about “accurately” grabbing the right 30 years, but if you accomplish the feat then the results are equal vs 60 years. if you doubt me, try a countdown of 30-1, evenly spaced vs 30-1 and 1-30 evenly spaced, and I think the results are the same.

The negative AO has been shown in peer reviewed papers to mitigate ice melt. Based on that research, I predict an average ice melt pattern this summer. No excessive melt and no supersized fast ramp out Fram Strait. One of the ways that this may happen is that a negative AO may cause 1 and 2 year old ice to compact and pile up, becoming quite thick in the span of one ice season. Maybe even thicker than multi-year ice.

There has been some discussion about how the baseline is calculated. To me that appears fairly irrelevant. What matters is the *shape* of the curve in recent weeks. Irrespective of how the baseline is calculated, the actual shape of both curves should be fairly similar, assuming they are both accurate and honest.
We know that the NSIDC curve was heading straight for the average, and then data from previous days was adjusted so that the trend took a sharp downwards turn. There may be valid reasons for adjustments, but it does seem suspicious that this occurred just as it seemed set to touch the average line. Of course, for the ice to be equal to the long-term average would be very embarrassing, particularly for the director of the NSIDC.
So, one organisation, which does not appear to be pushing AGW alarmism, shows the ice at the long term average. The other organisation, whose director is a prominent AGW supporter, shows the ice staying suspiciously below the average. Which organisation would you believe? I know which one I believe!
Chris

Bill Illis,
You said the following:
“I’m okay with the 1979 – 2000 baseline.
First, if you look back to the longer history of guess-timated sea ice extent, the 1979 – 2000 average is pretty close to the average ice extent over the long-term.
Secondly, we are supposed to be measuring the ice extent versus some period which was less affected by global warming (if we are to understand if it is lower now due to global warming).
Third, the satellite data that was specifically designed to measure sea ice extent started at the end of 1978 (although the satellite data actually goes back to 1972 and earlier) so a reasonably long period which is not as impacted by global warming (if there is such an effect) is 1979 to 2000.”
Now explain to me how any of what you said actually makes sense since human-induced global warming has supposedly been going on for 60-70 years now? If human-induced global warming started in earnest with the huge industrial boom following WW2, then we have NO DATA which is free of human influence so we have no baseline data to actually compare to, by your own argument.

Anu both the PDO and AMO have been shown to have an impact on arctic sea ice. Warm waters from a positive AMO from about 1999-2005 contributed strongly to the loss of ice on the atlantic side of the Arctic leading up to the dramatic 2007 loss. The AMO is now turning negative.
The PDO going into a cooler phase sees cooler ocean temps off the alaskan coast which has the effect of “blocking off” the warmer waters that develop in the west pacific from making it into Bering Sea.
So with the both the AMO and the PDO now appearing to go negative, yes I am fairly confident that we will continue to see increasing sea ice extent and the negative Arctic Ice anomalies were related to positive or warm phase of these cycles over the past 30 years. Nothing you have posted indicates otherwise.

Phil. (06:15:26) :
The sky is falling, hey Phil?

Luís (06:53:22) :
Even if using proper projections for this sort of analysis, but of different kind (e.g. Azimuthal vs Cylindrical) the results shall have to be different.
Lo and Behold, Luis, you are correct.
I did exactly as you suggest here: http://www.robertb.darkhorizons.org/TempGr/MarExtentVSArea.JPG
and the result was a Globe that is NOT uniformly warming, though it might be ever so slightly uniformly cooling, for the month of March.
For AGW to be correct, the Energy of Global Warming has to be found as a global budget surplus. March Polar Ice is not showing anything of the sort.

“One showed sea ice extent as normal, the other took sharp right turn just before it was expected to happen.”
Since the obvious difference between the algorithms is that one sees ice when the other does not we might also infer from this discrepancy that the the conditions exist to exacerbate differences in the behaviour of the algorithms; the ice in question is of marginal visibility, it may be there it may not.
Further more the algorithms introduce a systematic (or rather subjective) error in our measurements of ice extent. We don’t really know which is the most accurate even if both methods appear precise. Our knowledge of the true ice extent is likely to be in error by 500,000 km2 because we have to interpret satellite data rather than poking the sea with a stick. Minor changes or differences in absolute values as highlighted in this article are irrelevant since they are far smaller than the actual errors in knowing the true sea ice extent.
Fortunately we don’t need accurate measurements of ice extent to infer that the extent is decreasing decade by decade. We need precise data consistently interpreted over several decades to obtain an accurate measurement of how the ice is behaving without being fooled by noise. The data collected and published by climate scientists show very clearly the Arctic ice is melting and is not returning to the higher levels seen in the past.
This

rbateman (08:46:46) :
Rbateman, you are a lighthouse in the current Dark Ages.

On the same page cited in the top post, NSIDC explain their consistent use of the 1979 – 2000 baseline:

Why do you use the 1979–2000 average for comparisons?
NSIDC scientists use the 1979 to 2000 average because it provides a consistent baseline for year-to-year comparisons of sea ice extent. Scientists call this long-term average over a data series a “climatology.” If we were to recalculate the climatology every year to incorporate the most recent year of data, we couldn’t meaningfully compare between recent years. To borrow a common phrase, we would be comparing apples and oranges.
The problem with relying on a sliding average becomes clear over time, when we try to compare new years of data with previous years. For example, if we rely on a standard, unchanging climatology like 1979 to 2000, we can easily and clearly compare September 2007 and September 2008 with each other. However, if we were to use the sliding climatology of 1979 to 2006 for September 2007, and the sliding climatology of 1979 to 2007 for September 2008, we would no longer be comparing “apples to apples” when we compared the two years to climatology.
Finally, some scientists point out that since 2000, sea ice has declined precipitously. While you can do an average over any period, it is better to do so over a stable period, either a period of relatively flat change or cyclical change with little overall trend. If you include a strong increasing or decreasing trend when you calculate an average, you probably will not have a representative average.
That said, NSIDC has recently considered revisiting the 1979 to 2000 average. We now have thirty years of Arctic sea ice data. A thirty-year time series is a widely accepted scientific standard for a climatology because it is long enough to encompass most cyclical patterns of natural variation. The problem, however, is that we would have to deal with the potential confusion caused any time that a standard is changed. The graphs would look different to the general public and would require a great deal of explanation.
For those who are interested in comparing the thirty-year decline in Arctic sea ice extent to something different than the 1979 to 2000 average, the NOAA Arctic Report Card 2008: Sea Ice offers a graph showing groups of five-year averages from 1979 to 2008. What one immediately notices is that the overarching story remains the same: Arctic sea ice is rapidly declining over the satellite record, no matter how you calculate the averages.

This is consistent with the excerpt quoted in the article at the top of this thread:

NSIDC’s methods are designed to be as internally consistent as possible to allow for tracking of trends and variability throughout our data record

They then helpfully provide links to a number of other data sets, including ROOS.
More info here: http://nsidc.org/arcticseaicenews/faq.html

Also, the 1979-2000 data is still there too. Just delete the ‘.1979-2008’ from the URL’s.

For those who follow such triva:
The arctic sea ice has lost about 400,000 sq. km of ice since it’s annual peak on March 31, (even though as late as April 5th Rush Limbaugh continued to report that the arctic was gaining sea ice). But such trivia such as THE FACTS may not matter to certain folks…

Phil – {This is polite discourse, you should try making a presentation to a room full of Russian academicians!}
are they like macadamians? you know, nuts?
🙂

What a bunch of baloney.
Why are you focused on sea ice EXTENT rather than sea ice VOLUME?
It’s very dishonest the way you manipulate people… garbage in garbage out as proven by the following :”Both data gives about the same absolute amount of sea ice …” No, the above has nothing to do honestly looking at the “amount of sea ice”
REPLY: I always get a chuckle out of comments like these. A disagreement over presentation elevated at first contact to the “dishonest” presentation is a sure sign of a closed mind driven by dogma. Looking at your website strengthens that observation. -A

“Thickness has increased. Area has increased. What does that tell us about volume? What does that tell us about the “Arctic Death Spiral“?”
You’re the one who made the erroneous statement. You know very well you could clearly find out “what this tells us about volume” but you decided not to because the answer (shown by cook) would not support your narrative.
So Cook has zero credibility because he named his blog inappropriately? And because he doesn’t have enough comments right now? Of Course this blog has so many views, are you kidding me, there are tons and tons of people out there wandering the internet willing to jump on bandwagons without the scientific integrity to actual look up the core literature and make their minds for themselves. Look up conspiracy theories about UFOS and you’ll get just as many “views” on those websites.
Good strategy though regardless, attack and debate the credibility of someone when you have no response to the science.
This blog can be a good thing, a good way to investigate real scientific issues, but disingeniousness does not help advance the scientific understanding or method.
It is clear that there are far too many people who comment here without being willing to read up the actual literature. Individuals who are so eager to disprove what they are told by one side that they blindly follow the other.

“eh. not worried about what John Cook has to say. Especially when he pulls tricks like switching from a statement about extent to making it about volume. Heh. -A”
Really? What about…
“”So we will leave it up to the readers to do the math. Thickness has increased. Area has increased. What does that tell us about volume? What does that tell us about the “Arctic Death Spiral“?””
Don’t you think that statement is very disingenuous considering you lead people to believe that the volume is increasing and yet as Cook points out, the volume is still decreasing. You can attack his credibility all you like, but the truth is you shaped your argument to envoke skeptcism not true scientific thought. If you had, you would of clearly pointed out that the Volume for March 2010 was the lowest ever recorded for March? Once again, lets not let facts get in the way of science.

[snip] Calling the host of this site dishonest, without any facts, is unacceptable. ~dbs, mod.

Anthony says, “Note that 3+ (>2) year old ice has increased from 10% to about 14% during the past year, shown with the two black horizontal lines near the bottom. That shows an impressive growth of 40% relative to last year.”
1. How does >2 = 3+? What happened to 2.1? 2.5? Etc.?
2. 40% from one year to the next? How about that long climb from @ 82 – 86? Or 90 -91? Or – wow! – the rise in the 97 – 98 time frame! But the trend keeps heading downward…
3. The 40%, btw, is only 10% of what has been lost over the time of the trend. Much less impressive, isn’t it?
4. It should be obvious to all that the ice extent **does not** equal total ice. But this is what Anthony says, ” The implication being that ice thickness has been increasing for the last two years. Older ice is thicker ice.”
Incorrect. **Some** ice has increased in thickness, not all ice. A simple thought experiment: If 1% of the total ice is 5+ meters thick and this is lost through the Fram Straight, melts, whatever, but 1.5% more ice is >2m, but <3m, what have you gained? Nothing. This is essentially what Anthony is calling a significant rebound.
Also, we know from measurements made last year that ice that is of very poor quality is being measured as multi-year ice. http://www.time.com/time/health/article/0,8599,1956932,00.html
Anthony, why isn't this included in your post? Because it's about extent? Fine. But why focus on extent at all? It just isn't the more important metric.
5. The winter maximum, which is what Anthony is calling a rebound, is not very important in measuring ice health. The summer minimum is the gold standard for understanding change of ice health in the Arctic. Making a big deal of winter extent is a bit like Casanova getting excited about making it to first base on his date with the town floozie.
6. The Discrepancy: The difference between the two methods is a constant, Anthony, not a cumulative difference, so the difference will always be about the same, as opposed to your implication it is cumulative, "A half million here, a half million there, and pretty soon we are talking about real ice extent differences."
No, Anthony, pretty soon you are talking about the same half-million.
As ever, the trend is the thing, and the trend is down.
REPLY:
“Anthony says, “Note that 3+ (>2) year old ice has increased from 10% to about 14% during the past year, shown with the two black horizontal lines near the bottom. That shows an impressive growth of 40% relative to last year.”
No K. Obrien, you really should learn to read before citing. Steve Goddard wrote that. Regardless how you spin it, we have two years of recovery -A