There isn't all that much fake skeptic nonsense going round when it comes to Arctic sea ice. Climate risk deniers rather just ignore the geologic time scale event going on up North that could lead to an ice-free Arctic Ocean within one human lifetime. Still, every now and then an effort is made to trivialize Arctic sea ice loss. In this case it is done by averaging all daily sea ice extent numbers over the course of a year, and then claiming that Arctic sea ice is recovering.
The source of the claim is this graph based on MASIE data, which is the subject of this blog post. I'll get to that later, but here's the 'recovery' graph:
I'm not even going to link to the blog in question, because it's full of misleading and embarrassing statements by an older gentleman whose mind has obviously been set in concrete a while ago, and this particular nonsense has been taken apart by Tamino back in September. Of course this hasn't discouraged the blogger in question to stop misleading his readers, and his latest production of the useless annual average nonsense* has, again, been taken up by the free market fundamentalist ex-banker hobby organization known as the (no) Global Warming Policy Foundation.
All of this wasn't all that interesting to me until I compared the 'recovery' graph with an annual average graph based on JAXA sea ice extent data (found here):Here the trend line goes down instead of up, 2012 is lower than 2007, and 2015 has the 4th lowest annual average instead of 6th. That's quite a difference. What could be causing it?
Now, the MASIE FAQ page has this:
Use the Sea Ice Index when comparing trends in sea ice over time or when consistency is important. Even then, the monthly, not the daily, Sea Ice Index views should be used to look at trends in sea ice. (...) Use MASIE when you want the most accurate view possible of Arctic-wide ice on a given day or through the week.
In other words, don't use MASIE if you want to compare trends over time and be consistent.
The Sea Ice Index is basically NSIDC sea ice extent data that is used for the daily and monthly graphs shown on the NSIDC website and can be found here (the blogger calls it a NOAA product, which is confusing, and shows how intimately acquainted he is with Arctic sea ice data). Here's what daily NSIDC sea ice extent data shows when averaged for the year:
Again, trend is down, 2012 is lowest, and 2015 is 4th lowest. How about Cryosphere Today sea ice area data (found here)?
Trend line slightly downwards, 2012 lowest, 2015 4th lowest.
To top it off, here's the only freely available daily data left (as far as I know) that also tells us something about sea ice thickness. It's PIOMAS sea ice volume data (found here), which is modeled data, constrained by observational data that is assimilated into the model:
Trend line very much downwards, 2012 lowest, but 2015 is 6th lowest here too (after the 2013 and 2014 rebound years there was more ice during the first few months of the year). Mind you, this data runs up to November 30th, because the PSC hasn't released December data yet.
So, no data set agrees with MASIE. Here's another quote from the MASIE documentation page:
While operational analyses [like MASIE; N.] are usually the most accurate and timely representation of sea ice, they have errors and biases that change over time. If one is interested in long-term trends in sea ice or how it responds to changing climate forcing, generally, it is best not to use an operational product, but rather one that is consistently produced and retroactively quality controlled.
Does this explain the differences between MASIE and all other available daily data sets out there? Or are there other reasons as well? I can't imagine that just because of the human component in MASIE data construction (analysts trained in remote sensing imagery interpretation and sea ice climatology) an interannual comparison can be so different from those of other more consistent data sets.
Either way, even if an annual average graph wouldn't be a very poor and silly basis for claiming recovery, you still shouldn't be using MASIE data to do so. That the GWPF amplifies this misinformation by spreading it, is wrong and reprehensible. Remember who lied to you.
-----
* Why is it useless? That's simple. It doesn't tell us all that much about the health of Arctic sea ice. It's like measuring your weight every day from Jan 1st to Dec 31st. You're really overweight at the start year, then you stop eating for half a year and you get really thin and undernourished, followed by a junkfood binge after which you're overweight again. But then you take the average of all those daily weighings, and presto, your average weight is perfect! But, one might ask, how's your health?
What an annual average is basically showing us, is that winter still exists, and that when a lot of sea ice is lost over the course of a melting season, the regrowth curve of ice will also be spectacularly steep. But it tells us nothing about the maximum, and more importantly the minimum and the period preceding it when there's lots of open water absorbing solar radiation, further heating up the Arctic. The other problems with this kind of data misrepresentation, is that 10 years (MASIE data collection started in 2006) is too short a time frame for meaningful trend lines, and that sea ice extent is a two-dimensional measurement that doesn't tell us anything about sea ice thickness or volume.
One reason for 2007 being lower than 2012 on the MASIE graph may be explained in this 2015 paper by Walt Meier et al.: How do sea-ice concentrations from operational data compare with passive microwave estimates? Implications for improved model evaluations and forecasting (PDF)
Due to GAC-2012 some ice wasn't picked up by JAXA and other SIE products, that was picked up by MASIE.
Posted by: Neven | January 03, 2016 at 12:10
Hi Neven, you might be interested in this and the comments: http://euanmearns.com/will-the-ice-in-the-arctic-ocean-disappear/
Apparently ice won't melt as the world gets warmer ;)
Posted by: D | January 03, 2016 at 14:41
The paper linked above gives some detail about why the MASIE data may be different from other measurement products based on different grid resolution and measurement methods.
But I think your 'weight loss' comparison is also a good metaphorical explanation of the situation.
I am reminded of that frequent 'sceptical' trope that there is now MORE ice forming every winter in the Arctic than ever before. Especially after years when the summer low has been a record.
Posted by: D | January 03, 2016 at 15:04
Good article.
But I always feel that the non-expert deniers or confusionists... whatever, are handled with kid gloves; too politely. Any 9-year period where clearly the year-to-year fluctuations are as large or larger than the distilled "trend", does NOT show a trend. The clutz says, well, the data is the data and he cannot help that it shows a decreasing trend. No. It shows no trend. Period. This is the same issue I had (even worse) with actual climate scientists taking seriously the so-called pause between 1997 and 2013. Tamino has analyzed this too. Fluctuation is too large to say there is a trend. One needs no sophisticated statistical analysis to see this. Look at the noise. Now look at how large you say the trend is. Not larger? No trend.
Posted by: RICK BAARTMAN | January 03, 2016 at 22:35
I've got to take issue with your formulation, Rick, though the overall point is correct.
Stated the way you have done, there would be 'no trend' in the UAH temperature record, for instance: its calculated value is 0.11 C/decade, but if you look at the anomaly values for 1998 (0.42 C) and 1999 (-0.05 C), you will find a 'fluctuation' of 0.47 C, or more than four times the decadal trend. Yet as you know, the reported UAH is indeed robust and statistically significant.
Posted by: Kevin McKinney | January 04, 2016 at 05:00
Well, the Walsh and Chapman historical sea ice cover graph certainly isn't perfect, but I feel the writer of the piece goes about it the wrong way. He quotes a lot of old papers that are about Nordic seas (maybe the NIPCC report was a source of inspiration), and the graphs are all about different time frames, different months of the year (not entirely clear), different areas of the Nordic Seas, etc. It's a bit of a jumble, used to arrive at a pre-determined conclusion.
I believe there are a couple of posts on Diablobanquisa's blog that are much more worthwhile when it comes to this subject.
As for the comment section. If someone mentions Steven Goddard as a reliable source and nobody counters it, it's clear that both writer and commenters don't have a very broad grasp of the issue. And there's some other nonsense in there as well.
Posted by: Neven | January 04, 2016 at 09:09
Things are getting more embarrassing over on the blog where the annual average nonsense is posted. It seems the comment section has been closed, and my final comment hasn't appeared in it (it seems "Tamino’s (Foster’s) attack dogs" have been posting too, but we'll have to take Ron Clutz' word for it). I'm fine with deleting or not posting my comments, but how about being transparent about that?
Anyway, here's my final comment (I copied it, because I had a feeling the blogger would pull this trick) before I react to the nonsense in the blog post's update:
Posted by: Neven | January 04, 2016 at 09:30
And now some nonsense from the update:
I don't abhor operational products (or navigational observations, as Ron Clutz calls it), I just don't think that they're reliable enough for interannual comparisons. That's what my whole blog post is about (see the quotes from the MASIE product and documentation pages), and Ron Clutz has been told this many times now, but he keeps using MASIE for his interannual comparisons. First I thought it was because he was old and heavily biased, but given his behaviour I begin to suspect he does it to mislead people.
Here again Ron Clutz shows his ignorance, and admits his previous ignorance about who is actually producing the Sea Ice Index (NSIDC, not NOAA).
JAXA puts out data from its own AMSR2 sensor on its own Shizuku (GCOM-W1) satellite.
DMI, and NORSEX too I believe, uses data (via OSI SAF)from the SSMIS sensor aboard the DSMP-F17 satellite, which is part of the US DoD's Defense Meteorological Satellite Program. The NSIDC (not NOAA) uses SSMIS data too for its Sea Ice Index.
Different algorithms, different resolutions and different land masks. But all of this remains consistent from year to year, which is why all graphs in my blog post show the same curves and trend. MASIE, on the other hand, looks different, because it isn't consistent from year to year. And it doesn't need to be, because it isn't intended to be used for "comparing trends in sea ice over time or when consistency is important".
Ron Clutz knows this, but he persists in using MASIE data the way it isn't intended to be used. He is knowingly misleading his readers.
Posted by: Neven | January 04, 2016 at 10:03
And if Ron Clutz (or his misled readers) don't believe me, they can read this explanation on WUWT by Walt Meier, which also tells us more about the subject of this blog post:
Now, if Ron Clutz is a man of honour, he will correct his blog posts and stop spreading his misleading, meaningless, MASIE-based annual average nonsense.
Posted by: Neven | January 04, 2016 at 10:08
Great entry and great seeing you fighting for it Neven!
Posted by: John Christensen | January 04, 2016 at 12:52
MASIE, as I understand it, is a product aimed at providing digital data of the SeaIce extent as determined for use in Maritime Sector. This means that actual definition of what constitutes Sea Ice is different from that which is used in Arctic Research (afaik). For example the edge of the extent is an area that has enough Ice present that may pose a risk to people working at sea. The MASIE GIS layers do not contain any Sea Ice density data. Therefore when I use them I combined them with RTOFS Sea Ice model data to get and idea of what is going on. In short, MASIE should not be used to look at trends in Sea Ice as it is derived from data used for Sea/Arctic Safety purposes.
Posted by: SnaggyD | January 04, 2016 at 14:37
To be honest, Neven, none of these extent plots differ much. The anually averaged extent has not really changed in ten years.
However, the killer one is the volume variation. That is problematic evolution. And one not shown here which is the minimum extent in September and that goes on par with the loss of ice volume.
That alone is sufficient argument.
Posted by: navegante | January 04, 2016 at 14:40
I think that the most useful plots are decadal; ten-year averaging eliminates most of the "weather" fluctuations are is more revealing as to "climate" trends. For example on the basis of these I would differ with navegante's assertion that "anually averaged extent has not really changed in ten years" :
Arctic Ice extent(IJIS2): http://i713.photobucket.com/albums/ww133/Sane_Person/Arctic%20Meltdown/Sea_Ice_Extent-IJIS2-Arctic_zpsp5xqgf4c.jpg
Arctic Ice Area(CT): http://i713.photobucket.com/albums/ww133/Sane_Person/Arctic%20Meltdown/Sea_Ice_Area-CT-Arctic_zpsobz6vtfn.jpg
Contrast the Antarctic: http://i713.photobucket.com/albums/ww133/Sane_Person/Arctic%20Meltdown/Sea_Ice_Area-CT-Antarctic_zpsxp5ognsg.jpg
The important information in all three of the above are the grey and black curves. I really think it would be more revealing for the NSIDC to use decadal averages rather than show the "standard deviations" getting ever larger. How much sense does it make when the "mean" is undergoing a systematic time-dependent decline to use all 36 years of the data to get standard deviations?
Posted by: Tim | January 04, 2016 at 22:15
These plots take a while to load, if readers get impatient, I'll post lower-res pics!
Posted by: Tim | January 04, 2016 at 22:17
Same plots, lower resolution:
Arctic Ice extent(IJIS2):
http://i713.photobucket.com/albums/ww133/Sane_Person/Arctic%20Meltdown/Sea_Ice_Extent-IJIS2-Arctic-lr_zpstzvapbsa.jpg
Arctic Ice Area(CT):
http://i713.photobucket.com/albums/ww133/Sane_Person/Arctic%20Meltdown/Sea_Ice_Area-CT-Arctic-lr_zpszmydhmjn.jpg
Antarctic (CT):
http://i713.photobucket.com/albums/ww133/Sane_Person/Arctic%20Meltdown/Sea_Ice_Area-CT-Antarctic-lr_zpsybrzcc4n.jpg
Posted by: Tim | January 04, 2016 at 22:30
Ron Clutz obviously doesn't like people quoting facts at him with links to the actual MASIE FAQ page. My comment their (would have been comment #917) was never displayed.
Posted by: Kevin O'Neill | January 05, 2016 at 01:42
Neven, I admire your restraint and patience with this guy Ron Clutz.
Posted by: Rob Dekker | January 05, 2016 at 07:13
Good point Tim, and no doubt the negative trend decade to decade of average extent.
That guy selected the years (and the product in particular) very carefully to give a false impression. Cherry picking at its best. Probably the same kind of person that would go around saying that to extract any meaningful conclusion about climate you have to wait 100 years.
Truth is when you see the curves of ice extent evolution along the year,the last 10 years are pretty much bundled each on top of the others. 2012 had exceptional low but was way above average in March and April. 2013 had a very high max. And so. But the Winter ice is a blanket that is covering a very ugly reality. Denialists use that blanket to say "business as usual in the Arctic". But how to explain the albedo amplification, the dipole anomaly, and the loss of ice volume to someone that wants to stay on surface of things or that doesnt wanna listen. Ultimately I think myself, is it a battle worth to be fought?
Anyway the decade 2015 - 2025 is gonna be very different in terms of average, warming is unstoppable and Arctic amplification is well established.
Posted by: navegante | January 05, 2016 at 11:42
Well, on his avatar he seems friendly enough, so I thought I'd give him the benefit of the doubt. But he is knowingly lying and misleading.
I mean, here's the latest remark on his blog:
MASIE has a day-to-day or week-to-week story to tell to people who depend on conservative estimates of where there is ice in places like the Northwest Passage or Svalbard, etc.
MASIE doesn't and cannot have a year-to-year story to tell, because of the subjective element (human analysts) and changing methods over time (see Walt Meier's explanation above).
Ron Clutz knows this by now, but he still wants to continue to tell this story, even though all MASIE documentation states that you can't do it like this. He is knowingly misleading people.
Clutz could use all the other graphs I've posted in this blog post (yes, I did all the work and had to explain to Clutz where all the data comes from) as they can be used for interannual, consistent comparisons. But of course, they paint an entirely different story. Never mind the fact that 'annual average' is a silly metric that doesn't tell the whole story.
I just hope that not too many people fall for this scam. It's a very serious issue that could cost a lot of money and lives in the not too distant future.
Posted by: Neven | January 05, 2016 at 15:43
"I'm looking at all 12 months, not just September."
By coincidence I updated the 12-month cycle plot yesterday, following NSIDC publication of December 2015 monthly data. This shows the visible decline in both area and extent for every month of the year, 1979 to 2015.
http://img.photobucket.com/albums/v224/Chiloe/12_Climate/2015_Cycle_Arctic.png
Posted by: L. Hamilton | January 05, 2016 at 17:21
Larry, it seems I can't copy that png. Could you send it to me (for the ASIG long-term graphs page)? Thanks.
Posted by: Neven | January 05, 2016 at 23:54
Neven said
You can bring a horse to water, but you can't make it drink.
Posted by: Rob Dekker | January 06, 2016 at 07:34
Sent a clean copy of the cycle plot to Neven, so hopefully that's forthcoming on the long-term graphs page. If anyone else wants the file, send me a note.
Larry
Posted by: L. Hamilton | January 06, 2016 at 15:47
As a complement (and as a compliment) to Larry's cycle graph, one can also look at the BIST diagrams available on the NSIDC website.
http://nsidc.org/data/bist/bist.pl?config=seaice_extent_trends
I usually have this set up with two columns, one each for the Arctic & Antarctic. With "extent trends" selected in each column, and 12 rows requested, this will then display the trend pattern for each month (i.e. Jan - Dec) in an individual row.
Posted by: Bill Fothergill | January 07, 2016 at 14:01
In the OP, Neven makes reference to the article Tamino produced on the 28th September. In this article, he (Tamino) points out the pathetic mistake of comparing an annual average with a year-to-date average.
Now, anyone can make a silly, slap-forehead-with-palm-of-hand mistake - I should know, as I've made more than a few - but a reasonable person would acknowledge this when called upon to do so. An honest person, upon realising such an error, wouldn't even wait until they were called out on the matter. However, refusal to recognise when one has made a daft mistake smacks of either intransigent stupidity or deliberate deception.
The offending mistake was from an article written a couple of days earlier. A numerical comparison demonstrating the magnitude of the error is most illuminating, and I just happen to have a little y-t-d tracker running on the CT Arctic SIA numbers. The relevant figures are...
y-t-d average on 26th Sep 2015 .... 9.282 million sq kms
y-t-d average on 31st Dec 2015 .... 8.914 million sq kms
That's close to 370 thousand sq kms difference!
...
It is a relatively minor effect, but one must also remember that leap years are somewhat affected by this kind of problem. On a leap year, the annual average is based on 366 days, rather than the usual 365 days for other years.
For example, in 2012, the rolling 365-day average ending on 31st December, is about 4 thousand sq kms lower than the rolling 366-day average. In 2008, the difference was about 7 thousand sq kms.
Although relatively minor, if one is genuinely trying to compare like-with-like, this effect distances 2012 slightly further from other years.
Posted by: Bill Fothergill | January 07, 2016 at 15:27
On a sidenote, the Austrian NASI blog is celebrating the new year by throwing the baby out with the bathwater:
http://guymcpherson.com/forum/index.php?topic=3234.0
Posted by: viddaloo | January 08, 2016 at 02:01
@Rob Dekker
"You can bring a horse to water, but you can't make it drink"
Alternatively;
"You can bring a denier to data, but you can't make it think"
Sorry - couldn't resist that one.
Posted by: Leslie Graham | January 08, 2016 at 05:13
Thanks, Leslie, for making the point !
Posted by: Rob Dekker | January 08, 2016 at 07:43
" ... but you can't make it think"
Nice one, Leslie
And belated best wishes to all - hope you had a peaceful and prosperous (or even preposterous) perihelion.
Posted by: Bill Fothergill | January 08, 2016 at 11:02
Damn, Vid, that was a heck of a trojan troll. Still I give you the reason in the little trascendence on the sign of the graphs trends (except for the annually averaged volume which is the only metric that cant be masked by winter ice).
Another thing I wanted to point out is that ice extent started its "landslide" in 1999 after el Niño 1997/1998 if you carefully watch the NDSIC plots of each month, rather than just after the 2007 crash. That was 16 years ago! Bad prospect for the next post Niño 2015/16 years?
Posted by: navegante | January 08, 2016 at 12:04
And:
You can lead a denier to water, but you can't make it sink.
Posted by: Andy Lee Robinson | January 10, 2016 at 14:10
I made another effort to bring Ron Clutz to water, but I'm quite sure now he knows what he's doing. In the link to the 2012 WUWT blog post where Walt Meier explains how things work with operational products, etc, a commenter called Ron C posts several references to NIC documentation.
But anyway, he's deleting my comments again (and his own comments to wipe out traces of the fact, which is a cowardly act), so I'm just posting the comments here for reference:
Ron C: To repeat, Neven’s criticism of MASIE does not apply to the product output since 2006, which NSIDC said was reasonably consistent as their reason for releasing the dataset.
---
Neven: So, it seems there is something of a contradiction on that documentation page. On the one hand IMS (the operational analysis product on which MASIE is partly based) is described as “relatively/reasonably consistent”, as you quoted, Ron. On the other hand on the same page one can read statements such as:
The best way to resolve this is to ask the NSIDC directly whether they think that MASIE can be used for interannual comparisons like you’re doing, Ron. I’d be willing to do this, but only on the condition that when the NSIDC says that MASIE is not the appropriate tool for interannual comparisons, you either stop doing so, or put up a clear caveat to inform people of the NSIDC’s stance on using MASIE for interannual comparisons.
Could you agree with that, Ron? If so, I’ll ask the NSIDC about this issue. Or you could do so yourself, of course.
---
Ron C: I will continue to follow the MASIE data coming out of the National Ice Center to see what it says about Arctic ice extents. No permission from Neven, Meier or anyone else is needed to analyze available data and draw conclusions. Nullius in verba.
---
[My next comment wasn't posted, but it was about how Ron C is not just following, but making his misleading chart and posting it without a caveat to inform his readers about what the NSIDC considers appropriate use of MASIE data; N.]
Neven: It seems my last comment hasn't shown up (there was no link, however). Could you please have a look to see if it got stuck somewhere, Ron?
---
Ron C: Neven, you keep saying the same thing. Enough already.
[Clutz then removed his own comment as well, and of course, my next comment hasn't shown up; N.]
---
Neven: I keep saying the same thing, because you keep refusing to acknowledge that you can't use MASIE the way you do and then claim a 'recovery' or a 'plateau', without letting your readers know that the NSIDC explicitly states in its MASIE documentation that interannual comparisons isn't an intended use. Either you stop doing it, or you put in the caveat. Anything else is misleading.
BTW, did you do anything to compensate missing dates? Or did you just divide a year's total by the total amount of days on which data was available?
Posted by: Neven | January 30, 2016 at 22:33
So, that was the referencing, now for the interesting bit (although it is a bit of a nitpick):
It turns out that MASIE data contains blanks on dates where numbers weren't reported. So, some years have 363 days, others 364, and 2009 has only 342 days. Clutz doesn't make the mistake of dividing the totals of all years by 365.
But if a year only has data for 342 days or 361 days (2014), the average is bound to change if you fill in the remaining 23 or 4 days (depending on the season). So, that's what I did. Here's an animation of the changes:
Only 2009's average changed markedly, from 10.82 to 10.95 million km2. The other changes are small. As for the trend line, R2 went down from 0.24 to 0.18, but I don't know enough about statistics to say if this really means anything.
Posted by: Neven | January 30, 2016 at 22:45
I'm not quite sure why you expend so much energy on Mr. Clutz, who happily "moderates" out of existence comments on his blog he doesn't care for.
However when his grossly erroneous calculations for 2015 were first plastered across the Twittosphere by the usual suspects I did produce this by now fairly familiar looking graph:
which can be viewed in close proximity to the NSIDC version at:
http://GreatWhiteCon.info/resources/arctic-sea-ice-graphs/#MASIE
Can you spot the difference? Can Ron for that matter?
Posted by: Jim Hunt | January 31, 2016 at 01:11
Because I'm annoyed, of course. Because he's the only source of misinformation wrt Arctic sea ice at the moment. And because the MASIE annual average graph differs so much from the annual average graphs of all other daily data products.
But as you repeat, an annual average doesn't convey the information shown in your minimum graph.
Posted by: Neven | January 31, 2016 at 09:30
P.S. Re Ron et al. see also:
http://forum.arctic-sea-ice.net/index.php/topic,578.msg69254.html#msg69254
et seq.
Posted by: Jim Hunt | January 31, 2016 at 09:39
He's the only source of misinformation wrt Arctic sea ice at the moment.
Actually some of the usual suspects are still up to their old tricks. Here's Rose channeling "Goddard" recently for example:
https://twitter.com/GreatWhiteCon/status/687919611539517440
Posted by: Jim Hunt | January 31, 2016 at 10:10
Ron still hasn't published my constructive comment, and the GWPF still haven't fixed their misleading headlines, so I'm afraid that I have to admit that I got a trifle annoyed also. I'm taking your name in vain in my latest rant Neven. I hope that's OK with you?
"The Great Global Warming Policy Forum Con"
See also "Snow White's" Twitter feed:
https://twitter.com/GreatWhiteCon/status/695176179322642432
Posted by: Jim Hunt | February 04, 2016 at 10:39
I'm not too vain for that, Jim. :-)
Posted by: Neven | February 04, 2016 at 10:46
I mean I'm vain enough for that, Jim. ;-)
Posted by: Neven | February 04, 2016 at 10:48
Not a lot of people know that Ron Clutz has yet to publish a single one of the numerous helpful comments I have left for him on his so called "Science Matters" blog, including one from yesterday.
Even fewer people know that I have just bumped into him somewhere else entirely:
http://archive.is/ICZib#selection-1031.0-1043.27
Posted by: Jim Hunt | February 20, 2016 at 20:04
@ Jim
Tee Hee
Posted by: Bill Fothergill | February 20, 2016 at 20:31
I'm having the proverbial whale of a time over there Bill. I can't type fast enough to keep up with them! By way of example see for instance:
https://archive.is/syz5k#selection-1151.0-1163.27
Posted by: Jim Hunt | February 20, 2016 at 22:13
Jim,
A few items you may care to point out to AndyG...
1)
The extent chart used in the First Assessment Report way back in 1990 was predicated upon 10% concentration. Therefore, all other things being equal, one would expect any anomaly swings to be greater than those seen using the current 15% threshold.
2)
On Fig 7.20 from the 1990 report, the peak of the smoothed anomaly gets down to about -0.35 or -0.4 million sq kms.
Using NSIDC figures, the average annual extent (not anomaly) for the period 1979-90 works out as 12.31 million sq kms. (That period starts from the deployment of Nimbus-7, with its SMMR instrument. The end date is set coincident with the end of the chart used in the 1st assessment.)
For the period 1991-2004, the average extent drops by a full 0.5 million sq kms to 11.81 million sq kms. (N.B. The half million drop is NOT a transient peak, but is the average across the entire period.)
For the period 2005-15, the annual average drops to 10.92 million sq kms.
In case your chum cannot work this out for himself, this means that, smoothed across the periods, there is about 1.4 million sq kms less ice during 2005-15 than there was during 1979-90.
I'll stress again that this is not a transient anomaly such as the dip at the LHS of Fig 7.20, its's effectively a horizontal line 1.4 million sq kms below the baseline.
3)
What possible bearing does ice extent during the early Holocene have upon today's situation? Does he think that, since wildfires have started naturally since the Great Oxygenation a couple of billion years ago, that the "supposed" crime of arson should be struck from the statute books?
Why stop at the Holocene? Let's jump back in time to before the Pleistocene Glaciation even began. What bearing does that have?
Posted by: Bill Fothergill | February 21, 2016 at 01:38
Thanks for all that most useful information. I wasn't previously aware of the 10% threshold. I wasn't an Arctic sea ice nutter in 1990!
However, for the moment at least, I'm waiting for him to reveal what it is he's so scared of. Pigs might fly?
Posted by: Jim Hunt | February 21, 2016 at 02:15
"Seekers of the truth" or "climate change sceptics", as they like to call themselves, often feel the need to refer to diagram 7.20(a) from the Working Group 1 contribution to the First Assessment Report dated way back in 1990.
https://www.ipcc.ch/ipccreports/far/wg_I/ipcc_far_wg_I_chapter_07.pdf
The reason for this love affair with that diagram is because it shows a slight downturn in Arctic Sea Ice. This graph containing the "unequivocal proof that AGW is a scam" runs from about 1973 to 1990, and does indeed have an early period which, when smoothed, (I think it's a 12 month rolling average) gets perhaps as low as 300k sq kms or so below the datum baseline.
What these "seekers of the truth" are strangely reticent to mention is the second of the paired graphs, namely 7.20(b). This pariah of the graph world relates to the Antarctic, and has the temerity to show an upward trend at the start of the measurement period. This reaches to about 1.3 million sq kms above the baseline.
I wonder why they're so silent about that one?
Anyway, for those interested in looking at the source data for these charts, it is available from the Naval Ice Centre, which is jointly run by NOAA, the US Navy and the US Coast Guard. (Obviously, the latter two organisations are well know for their subversive views, and long standing affiliation with those Commie bastards.)
http://www.natice.noaa.gov/products/ice_extent_graphs/arctic_weekly_ice_extent.html
Enjoy.
Posted by: Bill Fothergill | February 21, 2016 at 15:52
Thanks Bill. I once had a nice long chat with a senior officer from one of the subversive organisations to which you refer.
Here is a subversive recording of what he had to say for himself:
http://econnexus.org/the-economist-being-economical-with-the-truth-about-climate-change/
Posted by: Jim Hunt | February 21, 2016 at 16:12
Anyway, for those interested in looking at the source data for these charts, it is available from the Naval Ice Centre, which is jointly run by NOAA, the US Navy and the US Coast Guard. (Obviously, the latter two organisations are well know for their subversive views, and long standing affiliation with those Commie bastards.)
http://www.natice.noaa.gov/products/ice_extent_graphs/arctic_weekly_ice_extent.html
Enjoy.
NIC weekly sea ice charts from 1972 are available here: ftp://sidads.colorado.edu/pub/DATASETS/NOAA/G02172/gifs_weekly/
https://nsidc.org/data/docs/noaa/g02172_nic_charts_climo_grid/
Posted by: Diablobanquisa | February 22, 2016 at 16:34
@ Diablobanquisa
Due to the fact that I was away on a computer-free holiday late January to early February, I did not see Neven's reposting of your "September Arctic Sea Ice Extent: 1935-2014" article until my return.
You may therefore not have seen the very late comment I appended to the reposted article. (Or you may have already been aware of the data pertaining to Russian convoys during WWII.)
Posted by: Bill Fothergill | February 22, 2016 at 17:57
I hadn't seen your comment, thank you very much, Bill.
I was aware of the convoys during WWII, although not with so much detail.
Cheers
Posted by: Diablobanquisa | February 22, 2016 at 18:40