Models of projected Arctic sea ice decline.

[Juan C. García]

At the beginning of 2007, four scientists of the NSIDC and one of the National Center for Atmospheric Research (all at the University of Boulder, Colorado) wrote the article “Arctic sea ice decline: Faster than forecast” (1). This article showed that the models developed by IPCC overvalue the stability of the Arctic sea ice extent (SIE), so that the real melting of sea ice was faster than what the IPCC models were forecasting. They also published a graph that has become a continuous reference, showing the IPCC SIE models versus the real decline of sea ice. (Graph 1)

It is important to emphasize that this article was made six months before the new September 2007 SIE record, which means that the values of 2005-2006 trigger this criticism to the IPCC models.

After six years, having new 2007 and 2012 SIE records, they are developing new models but they continue to underestimate the actual melt. From my point of view, it is unacceptable that almost all the models put the Arctic sea ice free after 2100. Only the worst scenario has a sea ice free at 2060 (according to the definition of Arctic sea ice free happens when NSIDC SIE average is less than one million km2) (Graph 2) (2).

But instead of trying to change the IPCC forecast, I would like to propose another action. Now the USA National Climate Assessment and Development Advisory Committee (NCADAC) has a draft document to comment and it will become the Third Climate Assessment Report. So I want to propose that we seek to include a forecast of Arctic sea ice free, based on PIOMAS volume. The reviewing deadline is April 12, 2013.

What do you think? Do you agree that the IPCC models, as they are right now, are worthless? Would you like to make the effort to include a PIOMAS volume forecast on the USA Third Climate Assessment Report?

The link is: http://ncadac.globalchange.gov/

If we succeed, the UNEP also publishes an Annual Report and we can look to include the same forecast for the Year Book 2014.

(1) Stroeve, J., M. M. Holland, W. Meier, T. Scambos, and M. Serreze (2007), Arctic sea ice decline: Faster than forecast, Geophys. Res. Lett., 34, L09501, doi:10.1029/2007GL029703.
Publication History
Issue published online: 1 MAY 2007
Article first published online: 1 MAY 2007
Manuscript Accepted: 26 MAR 2007
Manuscript Received: 15 FEB 2007

(2) Graph taken from the “Federal Advisory Committee Draft Climate Assessment Report Released for Public Review”, “2. Our Changing Climate”, page 68. Green lines added to show 2012 September record and Arctic sea ice free at 1 million km2.

[Jim Hunt]

I agree Juan. See the latest paper by Valerie Livina and Tim Lenton, who also agree:

http://doi.org/kkq

See also the recently mooted "Arctic Sea Ice Forum Distributed Sea Ice Model"!

http://forum.arctic-sea-ice.net/index.php/topic,51.msg462.html#msg462

[crandles]

Chapter 22 Alaska and the Arctic

Key Messages
1. Summer sea ice is receding rapidly and is projected to disappear by mid-century.

I think that should generate quite a few comments from several of us.

[Juan C. García]

Even that there are several good comments and asseverations on the new documents, they failed to recognized how fast can the Arctic sea ice will disappeare. I don’t understand why the NSIDC changed their view from Arctic sea ice melting at 2030, to in the period 2030-2040. Even that it is only a few years, I would go to early 2020 or sooner (and I don’t like NSIDC extent as the official measurement, I will discuss this later).
But anyway, I don’t agree with the following quote of the UNEP Year Book 2013 (recently published, page 19):

The IPCC report warned that this could happen around 2100 (IPCC 2007). One extrapolation of recent trends suggested that September could be ice-free before the end of this decade (Wadhams 2012). However, the most common prediction is that this will take place around 2035 (Wang and Overland 2012).

http://www.unep.org/yearbook/2013/

[anonymous]

It will probably take some time until the famous SIE record guarded by the NSIDC gets replaced by a more skillful data set. The problem is SIE provides daily data measured by satellite using algorithms tested by the scientific community. There is nothing more robust or reliable. However, in terms of forecasting skills, we know, it fails. Also, assuming constant thickness or not mentioning assumed thickness at all is ridiculous.

Somehow, measuring sea ice using extent is like counting money and reporting we have 15 bills in our pocket. Essentially the lack of basic data makes us to sea ice illiterates. Despite the draft climate assessment ignores sea ice volume and thickness completely (check the author!), the Arctic 5 years research plan honors it: http://www.whitehouse.gov/sites/default/files/microsites/ostp/2013_arctic_research_plan.pdf

However, the situation is strange, to say the least. How would you react as a president when the Arctic melts out completely during your term, while at the beginning all scientific advisers told you it can't happen?

Would you accept 'Oups'?

[Jim Hunt]

ArcticIo - See my link over here. If Andrew Neil (an influential, albeit sceptical, political pundit here in the UK) is right Mr. Obama will be more than happy for renewables to be left in the dust of increasing US exports of shale oil and LNG.

[ChrisReynolds]

Do you agree that the IPCC models, as they are right now, are worthless?

No. I don't take them seriously for projection, but they have use for elucidating mechanisms and for attribution. It should be note here that projection does not just mean with regards Arctic sea ice. The Arctic will have such widespread secondary effects that regional climate projection will have to be treated with scepticism. Projection of global average temperature has such broad bounds that it may well still remain valid for a few decades.

Would you like to make the effort to include a PIOMAS volume forecast on the USA Third Climate Assessment Report?

Not really. When things happen they will happen. There is nothing like a kick up the derriere to wake people up.

[anonymous]

Would you like to make the effort to include a PIOMAS volume forecast on the USA Third Climate Assessment Report?

Not really. When things happen they will happen. There is nothing like a kick up the derriere to wake people up.

Chris, do you expect the report appearing on Amazon's bestseller charts?

[ChrisReynolds]

Did Lynas' Six Degrees or Hansen's 'Storms of my Grandchildren'

Even if the Arctic were to plummet below 1M this year I suspect the result would be the media saying 'ooh look isn't this interesting', then everyone would get back to reading the latest celebrity gossip on their Ipads.

But I'll leave it at that because such speculation is meant for one of the other boards I never get round to reading.

PS - interesting stuff over at the sea ice blog under the latest thread - cracks of dawn.

[Juan C. García]

Hi, Chris:

I know that it is frustrating to try to change the political respond to AWG. There are so many interests behind the “business as usual” economy. But I can give at least three reasons to express why we should react right now.

• Fourteen years ago I was reading articles like “The Mystery of the Missing Carbon” and I got concerned with subjects like the one on the following paragraph:

  If the world’s missing carbon is in fact being stored within the boreal forest, and if the present warming trend is turning the boreal forest into a source of carbon, then there could be a significant increase in the rate of carbon build-up in the atmosphere. Scientists fear that by the year 2100 the amount of carbon dioxide in the atmosphere might actually double pre-industrial levels (Wofsy 1999)–to more than 560 parts per million (the 1990 level was 353 parts per million).

  http://earthobservatory.nasa.gov/Features/BOREASCarbon/missing_carbon_4.php
  
  From my point of view, this could happen not at 2100, but much earlier (possibly 2025-2050). In fact, we are close to see it happen. It is not just carbon dioxide but methane, which is 20 times more powerful on a 100 year time frame, but 72 times more powerful on the 20 years time frame. If there are substantial emissions of methane to the atmosphere, I will say that the consequences will be enormous. So we cannot wait one more year to react.
• After more than five years of the Fourth Assessment Report, this year will be published the Fifth Assessment Report. If we see the models, I’m sure that most of us will agree that the IPCC models have a strong influence of deniers. Are we going to accepted that they will cover reality for another five years, until the Sixth Assessment Report?
• We are a community that is knowledgeable on Arctic sea ice and we are very worried about what we see that is happening. So we are the ideal group to react. Why should we wait?

Of course, the involvement will be a personal choice. But personally, I am not willing to wait. And I believe that as a group, we could make the changes that we cannot make as individuals. So the invitation is still there…

[Jim Williams]

1.  I agree with Chris that it's a waste of time to try to change the models they're using, and
2.  this seems like a question which belongs under Policy, not Sea Ice.  We might want to discuss which models we want to rely on under Sea Ice, but not which models others ought rely upon.

[Juan C. García]

Jim Williams:

I agree that it is a waste of time to try to correct IPCC models and my proposal is not trying to correct them. What I am proposing is, as a group, to pursue  to include a PIOMAS volume graph -showing the historic values and the possible tendency- on the following publications:

• Third Climate Assessment Report of the USA National Climate Assessment and Development Advisory Committee (NCADAC) (in review until April 12).
• The IPCC Fifth Assessment Report
• The UNEP year Book 2014
• Any official publication that will cover the Arctic sea ice melt on the following years

On the other hand, I agree that this topic could be changed to the category AGW, group Policy and Solutions.

[anonymous]

This paper describes in detail how sea ice was modeled for the Max Plank Institute. Reality check was done against sea ice extent and area (Bootstrap & NASATeam). It challenges volume decrease as modeled by PIOMAS and strongly supports an ice free Arctic only along high emission scenarios (RCP8.5) and surely not within next decades. The authors reject PIOMAS as a valid reference because:

Using the NCEP reanalysis, on which also PIOMAS is based, we find the same decay rate in summer sea-ice volume as the PIOMAS reanalysis. However, forcing MPIOM with ERA-Interim reanalysis, we find a 40 % smaller decay rate. This dependence of the modeled evolution of sea-ice volume on the particular choice of the atmospheric reanalysis indicates that a reliable estimate of sea-ice volume trends is currently not possible.

http://onlinelibrary.wiley.com/doi/10.1002/jame.20016/pdf

[ChrisReynolds]

Thanks Arctic.io,

Not overly impressed with the model, the ice has no heat capacity (unlike PIOMAS) and there is no attempt at sub-grid parameterisation of ice, PIOMAS use a probability density function for sub grid modelling of ice thickness and has a two layer model of ice which includes heat capacity. There are other issues but these I see as the most significant.

The biggest problems I have are that: The CryoSat 2 data along with ICESat now broadly supports the degree of loss shown by PIOMAS. Maslowski's NAME model uses ECWMF, not NCEP/NCAR, yet produces volume loss as aggressive as PIOMAS. And on reading the relevant section (pages X-29 to X-30) there are obviously further problems with the model.

I still think that PIOMAS is largely on the right track, and that years 2011 (when there was a loss of area not suggested by the weather) 2012 (when there was a new record that was not due to the August storm) are the result of the massive volume loss of 2010. And the agreement of ASCAT/DAM and PIOMAS after 2012 suggests that 2013 will be another massive loss.

[anonymous]

Not overly impressed with the model,

Me too, while reading I used left brain to memorize confessed deficiencies and right brain to book keep the bolder statements. Now both resist to talk to each other Too bad I can't simply run PIOMAS forced by ERA-Interim, I'd really like to know, so thanks for referring to NAME, very good point.

[OldLeatherneck]

I have one problem with leaving all of the current projections in the 'public domain', without any caveats, is that policy makers and citizenry at-large are going to assume that they have many decades to implement changes.

As an example, after retirement 5+ years ago, when I had the luxury of time to further my knowledge about AGW, I reviewed a large number of projections relative to Sea-Level Rise.  Base on what projections were available then, I was satisfied that civilization had 90 years (until 2100) to prepare for SLR of 12" -18".  Now I fear that we have less than 40 years (until 2050) to prepare for an SLR approaching 1 meter.

The policy makers and general public need to know the truth about how rapidly the arctic sea ice is declining and how imminent the resulting changes to weather patterns and sea-levels are going to be.

[Juan C. García]

I am not an expert in IPCC Arctic sea ice models, but let me know if I understood them correctly:

According to the table information, foot note 2, at 2005 we were at 375 ppm CO2-eq. So, if we assume that we increased 2 ppm CO2-eq each year, roundly we should be at 390 CO2-eq at 2012. Also, it is known that if we stop emitting GHG today, the world will continue warming. There is a time lag between the emissions and the complete effect that the GHG will have on our planet.

• Nevertheless, on the RCP 2.6 scenario, we can jump to 450 CO2-eq approximately at 2040, but the graph of the IPCC models shows (on average) that we will not significantly go under the Arctic SIE record establish at 2012.
• On the RCP 4.5 and on the RCP 6 we will increase to 650 and 850 ppm CO2-eq, respectively. That is, on the RCP 6 we more than double the CO2-eq that we have right now. But in both models the graph shows that we will not have (on average) an Arctic sea free of ice at 2090.
• Finally, in the RCP 8.5 we continue to build up GHG without any control. So in this scenario, the graph shows that we will have an Arctic sea free of ice (extent less than 1 million km2) at 2060 (almost half a century from now).

On the other hand, there is the possibility that we could have an Arctic sea free of ice in only eight years, that is, before 2021, if the 80% of the poll answers are right.
http://forum.arctic-sea-ice.net/index.php/topic,80.0.html
If I am wrong about this analysis, I will be happy if you let me know. But if I am right (and the forum members that are voting are also right), I would like to know if you share the concern that institutions -like the IPCC- are failing to accomplish their mission for which they were created (like making models that are credible).

[Juan C. García]

Results of the Poll Arctic sea ice free at March 5, 2013 2:36 PM

(Don't forget to give your vote)
http://forum.arctic-sea-ice.net/index.php/topic,80.0.html
(without "https")

[anonymous]

I would like to know if you share the concern that institutions -like the IPCC- are failing to accomplish their mission for which they were created (like making models that are credible).

Juan, it is not like this at all. Put simply, the IPCC' mission is to collect and assess all available knowledge about climate change plus its impact. Check http://www.ipcc.ch/organization/organization.shtml for details. No failure and no models here.

Models are useful to verify knowledge and estimate impact. However, the capabilities of a model can only be tested against historical and present data. In terms of sea ice extent/area - good data - they are getting better as you posted below. In terms of volume/thickness there is unfortunately not enough data, neither in time nor spatially to verify such a model.

PIOMAS, as a regional model, on the other hand - most readers here will agree - does a fair job modelling Arctic sea ice starting with 1979. But PIOMAS knows nothing about climate change and emission scenarios, so it won't tell us a thing about the future.

And here opens the gap: On one hand we have GCM modeler saying, look, it performs good against existing data and on the other hand we have people thinking extent/area tells only half of the story referring to PIOMAS.

I see two options 1) the scientific community agrees on an 'official' ice thickness data set incorporating all available data acquired from the bottom of the ocean up to satellites capable to verify GCM models or 2) we wait until the Arctic gets actually ice free, which will tell us a lot about PIOMAS.

To summarize: nobody is to blame for missing data, but everybody has a different strategy to deal with.

PS: What you might criticize is the reported level of confidence of statements like 'the Arctic becomes ice free earliest mid century'.

[Jim Williams]

PS: What you might criticize is the reported level of confidence of statements like 'the Arctic becomes ice free earliest mid century'.

I think this is the important point.  The 'public' doesn't understand the state of our lack of understanding, and nobody is explaining that we simply don't really know.

I will say that for the most part the sensitivity analyses and evaluations of risk under uncertainty are being suppressed, but that isn't really my topic of interest.  I've already decided that it is too late, and I'm convinced that what we are seeing now is basically the result of the Industrial Revolution 100+ years ago.  For the most part, I'm simply watching what happens now.

[anonymous]

Wanted to know whether the differences between NCEP and ERA-Interim reanalyses - mentioned below - are that significant and finally found http://cci-reanalyzer.org/Reanalyzer/index_tseries.php .

Here the DJF winter 2m Temps North of 70° from NCEP's V2 (1870-2010):



and ERA (1979-2012):



Would say comparability is rather low... What went wrong here?

[ChrisReynolds]

Arctic.io,

Annual Temperature north of 64degN.

From Climate Reanalyser.
ERA Interim


NCEP/NCAR V1


From NCEP/NCAR, monthly timeseries



NASA GISS (observational)


Conclusion, I won't be using the Climate Reanalyser because I don't understand why it disagrees with GISS, and NCEP/NCAR gives a very good match with GISS.

NCEP/NCAR timeseries.
http://www.esrl.noaa.gov/psd/cgi-bin/data/timeseries/timeseries1.pl
GISS Banded data.
http://data.giss.nasa.gov/gistemp/tabledata_v3/ZonAnn.Ts+dSST.txt

[anonymous]

Chris, sure, I'm not going to use -6°C as Arctic winter temp for anything. Still looking for the real difference between NCEP & ERA. I sent a mail to the address found at the footer of that page. Let's see what comes back...

[anonymous]

... what we are seeing now is basically the result of the Industrial Revolution 100+ years ago.  For the most part, I'm simply watching what happens now.

Jim, did you discuss that point with your children?

[ChrisReynolds]

In various papers ERA-40 is reported to be better than NCEP/NCAR in certain aspects. However it was some time ago that I noticed that NCEP/NCAR temperature matched GISS closely. So I'm happy to keep using it for temperature, and pressure (which is down to synoptic scale processes).

[Shared Humanity]

Jim Williams ......."I've already decided that it is too late, and I'm convinced that what we are seeing now is basically the result of the Industrial Revolution 100+ years ago.  For the most part, I'm simply watching what happens now."

I can't seem to figue out how to quote another. I am rather dense in this respect.

I agree with you Jim which is why I believe that every region of the world (By region, I mean areas which could be considered cohesive ecosysytems. They likely span national boundaries.) needs to develop and implement aggressive mitigation strategies now. They should include the capture and retention of water. Retention can best be accomplished by minimizing evaporation and transpiration. Techniques currently used in a rapidly disappearing climate regime are no longer appropriate. Dams in the southwestern U.S., for instance, encourage dramatic evaporation.

[Jim Williams]

I can't seem to figue out how to quote another. I am rather dense in this respect.

See the word "Quote" on the right side of the screen at the top of each post?  Click on it to start a reply with the whole post quoted.  We usually cut out most of the text.

While editing you can also "Insert quote" in much the same way.

... what we are seeing now is basically the result of the Industrial Revolution 100+ years ago.  For the most part, I'm simply watching what happens now.

Jim, did you discuss that point with your children?

My children are old enough to fend for themselves.  One of them might be stable enough to fend for me too.

[MOwens]

on climate models, sea ice, CO2, and surface air temperature: http://climatewatch.typepad.com/blog/2013/03/what-the-models-do-show.html

It looks to me like the models have the relationship right, but the magnitude wrong.

...using the GISS II model produced this relationship between CO2 and global sea ice (orange highlight is 2007-2013; total data set covers 1958 to 2100):


...while the historical relationship (1870 to 2007) is this:

[Juan C. García]

At the NSIDC August 6, 2012 Analysis, the NSIDC showed a graph with the SRESA1B models (that are part of the CMIP3 Models used in the IPCC 4th Assessment Report of 2007) and with the RCP 4.5 models (that are part of the CMIP5 models and could be use in the 5th Assessment Report to be published at 2013-14).
In this NSIDC August Analysis, the NSIDC said:

Previous research at NSIDC documented that September Arctic ice extent has declined faster than models predicted it would. The comparison was between observations and simulated trends from models participating in the World Climate Research Programme Coupled Model Intercomparison Project Phase 3 (CMIP3). These climate models were used in the 2007 4th Assessment report of the Intergovernmental Panel on Climate Change (IPCC). In a new paper, Stroeve et al. (2012) compared the observed 1979-2011 September trend for the Arctic against trends over the same period from the next generation of models in the CMIP5 archive. While the newer CMIP5 models do a better job of simulating the observed trend, most of the modeled ice extent trends are still smaller than the observed downward trend. NSIDC is working with researchers to further improve the models, which help extend and refine our understanding of the climate system.
Credit: National Snow and Ice Data Center courtesy Stroeve et al. 2012

http://nsidc.org/arcticseaicenews/2012/08/a-most-interesting-arctic-summer/

On the other hand, on Stroeve et al. 2012 we have (4. Discussion and Conclusions):

If we constrain the analysis to models that (based on criteria described earlier) can reproduce the observed climatological mean September ice extent, the spread in projected ice extent throughout the 21st century from the CMIP5 and CMIP3 models is similar. This holds despite the overall better match of the CMIP5 models with the observed seasonal cycle and trend. Furthermore, a similar number of these ensemble members reach nearly icefree conditions (less than 1.0 x 10⁶ km²) before the end of the 21st century. Viewed in this context, conclusions drawn from CMIP5 are not much different than those from CMIP3.

http://www.uib.no/People/ngfhd/EarthClim/Publications/Papers/stroeve_etal_2012.pdf

On this regard, I included the graph published in the NSIDC August Analysis, but with the following changes made by myself:

• The graph is updated with the new 2012 SIE record (yellow line)
• I made explicit that the new 2012 record is ahead 50 years of the CMIP3 SRESA1B (2007) models, but also 20 years of the CMIP5 RCP 4.5 models.
• Finally, I highlight that roughly at 2030, the difference between the two types of models is around 2.25 million km², while at 2100 this difference decreases to only 0.5 million km².

Would that be reasonable? Or are the models being forced so that they follow the real values that we are having on the last ten years, but then they are also being force so that they do not have an ice-free at 2100?

[Juan C. García]

Do the models are based on Arctic sea ice extent or are based on Arctic sea ice volume?
This image is a suggestion to the Slogan contest and I surely believe it is important to highlight that we have lost more than 50% of Arctic sea ice.
I invite you to participate in the Slogan contest that is ending at March 15th, 2013.
More information on Neven’s Arctic Sea Ice Blog:
http://neven1.typepad.com/blog/2013/01/slogan-contest.html

[Juan C. García]

For those who are entering the Forum as Guests (not registered as Users), seems that you are not able to see the attachments, so you are not able to see the graphs that I have put on this blog. I will look to put the next graphs as “images” instead of attachments. Seems that images work better and you will be able to see them.
But anyway, other users can put attachments (that are simpler to put on), so I invite you to register to the Forum.

[Juan C. García]

I will be writing about the characteristics of NSIDC SIE monthly averages and the difficulty of reaching less than one million km2 of sea ice extent. So I just want to show how it is the poll right now, before I start to talk about it.

https://forum.arctic-sea-ice.net/index.php/topic,80.50.html

[Juan C. García]

On their November 2012 analysis, NSIDC made public:

Average ice extent for October was 7.00 million square kilometers (2.70 million square miles). This is the second lowest in the satellite record, 230,000 square kilometers (88,800 square miles) above the 2007 record for the month.

(Green and red straight lines added by myself)
Quote and Graph: http://nsidc.org/arcticseaicenews/2012/11/

I couldn’t understand the 7 million km2 assigned as October 2012 average by NSIDC, for two reasons:

• NSIDC official October 2012 average was above October 2007 average, but the first fifteen days of October 2012 where substantially below 2007, while the second part of the month where just slightly above 2007 (and not for all of the fifteen days).
• If we analyze 2012 alone, the October values where substantially lower than 7 million km2 for the most part of the month, so how can it be that the average was 7 million km2?

I was wrong in my conclusion, but I thought that the October average was 6 million km2 and someone at NSIDC, by mistake, made it 7 million km2. I wrote comments at Neven’s Arctic Sea Ice Blog and I also wrote to NSIDC. Thanks for the answers of Wipneus (1), NLPatents (2) Piotr Djaków (3) and NSIDC (4), I found that NSIDC was not using the statistical monthly average, that is, the NSIDC monthly average is not the sum of the daily values of a month, divided by the days with value on that particular month.

(1) http://neven1.typepad.com/blog/2012/10/looking-for-winter-weirdness-2.html?cid=6a0133f03a1e37970b017d3d564252970c#comment-6a0133f03a1e37970b017d3d564252970c
(2) http://neven1.typepad.com/blog/2012/10/looking-for-winter-weirdness-2.html?cid=6a0133f03a1e37970b017ee4ceaf7e970d#comment-6a0133f03a1e37970b017ee4ceaf7e970d
(3) http://neven1.typepad.com/blog/2012/11/ct-sia-finally-above-2-million-km2-anomaly-mark.html?cid=6a0133f03a1e37970b017ee4ddeda8970d#comment-6a0133f03a1e37970b017ee4ddeda8970d
(4) http://neven1.typepad.com/blog/2012/11/ct-sia-finally-above-2-million-km2-anomaly-mark.html?cid=6a0133f03a1e37970b017d3d6af897970c#comment-6a0133f03a1e37970b017d3d6af897970c

Instead, NSIDC calculates the monthly average and makes a graph of the monthly sea ice extent, according to the following criteria:

2. Overview of Sea Ice Index Processing
…
Mean Concentration Fields and Median Ice Edge Position
On monthly extent images, ice ends and water begins where the concentration estimates of grid cells in the gridded average, or mean, concentration field for that month drop below 15 percent.

http://nsidc.org/data/docs/noaa/g02135_seaice_index/index.html

As I understand now the NSIDC monthly average, in a 30-days month the 15% is 4.5 days, in a 31-days month the 15% is 4.65 days and in a 28-days month the 15% is 4.2 days. To explain it with rounded numbers, if a grid cell is with 100% of ice during 5 days, that grid is going to count as 100% ice for the entering month. It can also have 50% of sea ice for 10 days or 15% for the whole month. Both will also count as 100% for the entering month. If it is 4 days or less, then the grid cell will count as 0% of sea ice for the entire month.
Finally, if a grid cell on October 22nd has 10% of sea ice, on October 23rd has 20%, and so on until October 30th with 90% and October 31st with 100% of sea ice, then this grid cell will also count as 100% with sea ice for the whole month. More or less, that is what happens on October 2012. Even that it was just slightly above 2007 for a few days, these days where on October 20th – 26th and it meant that several 2012 grid cells qualify as 100% sea ice for the month, but this didn’t happen in the same magnitude on 2007.   

Basically, the rule that NSIDC uses to calculate what I will be calling the “Official NSIDC Monthly Average” tends to over valuate the average, if it is compared with what I will be calling “The Daily Values Average” that will be the statistical average based on the sum of the daily values divided by the numbers of days with a value.
The overvaluation is especially true during the months where there is a fast freeze up or a fast melt, as it happens in October and July, respectively.

[Juan C. García]

Difference between NSIDC Official Monthly Averages and the Daily Value Averages by month (2012)

[Juan C. García]

I usually don't like to say "I said it" but this time I will:

After six years, having new 2007 and 2012 SIE records, they are developing new models but they continue to underestimate the actual melt. From my point of view, it is unacceptable that almost all the models put the Arctic sea ice free after 2100. Only the worst scenario has a sea ice free at 2060 (according to the definition of Arctic sea ice free happens when NSIDC SIE average is less than one million km2)

From the NOAA's News "Arctic nearly free of summer sea ice during first half of 21st century"
http://www.noaanews.noaa.gov/stories2013/20130412_arcticseaice.html

We can jump to the following article abstract made by James Overland of NOAA’s Pacific Marine Environmental Laboratory and Muyin Wang of the NOAA Joint Institute for the Study of Atmosphere and Ocean at the University of Washington:

Abstract
[1] The observed rapid loss of thick, multi-year sea ice over the last seven years and September 2012 Arctic sea ice extent reduction of 49 % relative to the 1979-2000 climatology are inconsistent with projections of a nearly sea ice free summer Arctic from model estimates of 2070 and beyond made just a few years ago. Three recent approaches to predictions in the scientific literature are: 1) extrapolation of sea ice volume data, 2) assuming several more rapid loss events such as 2007 and 2012, and 3) climate model projections. Time horizons for a nearly sea ice free summer for these three approaches are roughly 2020 or earlier, 2030± 10 yrs, and 2040 or later. Loss estimates from models are based on a subset of the most rapid ensemble members. It is not possible to clearly choose one approach over another as this depends on the relative weights given to data versus models. Observations and citations support the conclusion that most Global Climate Models results in the CMIP5 archive are too conservative in their sea ice projections. Recent data and expert opinion should be considered in addition to model results to advance the very likely timing for future sea ice loss to the first half of the 21st century, with a possibility of major loss within a decade or two.

doi: 10.1002/grl.50316
http://onlinelibrary.wiley.com/doi/10.1002/grl.50316/abstract