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Author Topic: Latest PIOMAS update (October 2019)  (Read 1044802 times)

oren

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Re: Latest PIOMAS update (July 2019)
« Reply #3050 on: September 22, 2019, 12:23:27 PM »
Making a probable summation, Beaufort + ESS + CAA should be around 250 km3 by the minimum (compared to 50km3 for 2012), and Greenland Sea another 250 km3. Adding the CAB should get the total to less than 4400 km3, with the lower limit not well defined.

Overall, I expect 2019 to pass 2016 (4400 km3) and 2011 (4300 km3) and reach 2nd place in volume. I'd be quite surprised if it manages to break 2012's 3670 km3 record.
In reality, Beaufort + ESS Laptev + CAA was a low 180 km3, and with Greenland Sea the minimum volume outside the CAB was a meager 290 km3 (similar to 2012 on minimum date and a bit lower than 2011's 320 km3). This helped to clinch the 2nd lowest title, which totaled a very respectable 4050 km3, but as expected did not break 2012's record.

All in all, the predictions were not far off the mark (but had I known in advance that August melting would be so poor I would have predicted higher numbers).

Wipneus

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Re: Latest PIOMAS update (October 2019)
« Reply #3051 on: October 05, 2019, 08:57:45 AM »
PIOMAS gridded thickness data has updated. Volume calculated from thickness was 4.57[1000km3] on 30th September, second lowest for the day.
The 2019 minimum was around the 10th, 4.06[1000km3]. As these number are not exactly the same as the official PIOMAS volume numbers, wait for the release of those.

Here is the animation.


Wipneus

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Re: Latest PIOMAS update (October 2019)
« Reply #3052 on: October 05, 2019, 09:04:04 AM »
The volume and volume-anomaly graphs.

Wipneus

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Re: Latest PIOMAS update (October 2019)
« Reply #3054 on: October 05, 2019, 09:13:14 AM »
More graphs to prepare (the ones with annual minimum), but that will be much later. Paint job to do.

blumenkraft

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Re: Latest PIOMAS update (October 2019)
« Reply #3055 on: October 05, 2019, 09:14:28 AM »
Thanks a million, Wipneus! :)
Refugees welcome

Shared Humanity

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Re: Latest PIOMAS update (October 2019)
« Reply #3056 on: October 05, 2019, 06:28:35 PM »
Your delivery of data in a consistent manner like a finely tuned Swiss watch is what makes this site so valuable to the rest of us. I cannot thank you enough. I now anticipate the other members here who use the data to provide other insights.

I am a spectator here and value all of you who do the work you do. It is not lost on me how much time you take to do this.

Jim Hunt

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Re: Latest PIOMAS update (October 2019)
« Reply #3057 on: October 06, 2019, 12:49:08 AM »
PIOMAS gridded thickness data has updated.

Thanks very much Wipneus.

Since I’m currently involved is a heated “debate” about Arctic sea ice trends over at ex Prof. Judy’s, here’s an added bonus. The September monthly volume trend:

http://GreatWhiteCon.info/2019/10/facts-about-the-arctic-in-october-2019/#Oct-05
Reality is merely an illusion, albeit a very persistent one - Albert Einstein

slow wing

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Re: Latest PIOMAS update (October 2019)
« Reply #3058 on: October 06, 2019, 05:35:49 AM »
Thanks Wipneus!

The September monthly volume trend:

Thanks for this plot. There is clearly some year-to-year correlation but, that aside, it seems to me that the Arctic sea ice volume data seems reasonably well described by a linear decline.

Eye-balling, it looks like it reaches zero volume in about 10 years time (and may fluctuate down to that sooner). I wouldn't rule that out!

Stephan

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Re: Latest PIOMAS update (October 2019)
« Reply #3059 on: October 06, 2019, 08:30:16 AM »
Thank you Jim for the link. [http://GreatWhiteCon.info/2019/10/facts-about-the-arctic-in-october-2019/#Oct-05]. From the two graphs it can be easily ruled out that sea ice thickness (expressed as volume divided by extent) Sept 2019 has been lower than in Sept 2012.

El Cid

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Re: Latest PIOMAS update (October 2019)
« Reply #3060 on: October 06, 2019, 08:48:16 AM »
The September monthly volume trend:



The trendline on this chart is obviously faulty.

A trendline is right if the datapoints are more or less randomly distributed above and below the trendline - this is simple statistics. If the datapoints are not randomly distributed above and below the trendline then it is
a) not a linear trend
b) the dataset is not right

In this case I suspect a), since from 1985-2005 all datapoints except 2 are above the trendline and then 6 consecutive ones are below. This is clear signal that this linear trend is not OK.
Also, volume is not going anywhere these past 10 years. 

b): Everyone uses the data from 1979 and creates linear/polinomial etc.  trends starting there just because that is where the dataset starts. That is a pretty terrible reason to start the trendlines from that point. What if you had the data since 1950? What if only from 1990? Would you get the same result? of course not. First, you need to have some proof as to when (natural processes leading to) the volume reduction  actually started and start the linear trend from that point (eg from 1988 or what have you).

Summarizing: It is obviously statistically NOT a linear trend and even if it were the dataset used for them is probably not the right one.

Jim Hunt

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Re: Latest PIOMAS update (October 2019)
« Reply #3061 on: October 06, 2019, 09:02:00 AM »
The trendline on this chart is obviously faulty.

Did I mention that "I’m currently involved is a heated “debate” about Arctic sea ice trends over at ex Prof. Judy’s"?

The displayed linear trend was created using the Excel "TREND" function. Surely you don't want to start a "debate" with Microsoft too?

« Last Edit: October 06, 2019, 09:08:52 AM by Jim Hunt »
Reality is merely an illusion, albeit a very persistent one - Albert Einstein

binntho

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Re: Latest PIOMAS update (October 2019)
« Reply #3062 on: October 06, 2019, 09:07:30 AM »
The September monthly volume trend:



The trendline on this chart is obviously faulty.

A trendline is right if the datapoints are more or less randomly distributed above and below the trendline - this is simple statistics. If the datapoints are not randomly distributed above and below the trendline then it is
a) not a linear trend
b) the dataset is not right


I would caution against calling any trendline "right" - it's only a model, an attempt to decipher underlying tendencies and predict future values.

In this case, 18 datapoints are under the line and 22 above. Pretty near random. Long stretches are above or below, which can be explained by inter-annual memory in the system (i.e. a low year tends to be followed by a low year and vice versa - not necessarily true at all times but perhaps more likely to be true than not).

The linear trend is clearly not perfect, but I'd suggest that it is the best we can get given the paucity of data points. Any eyeballing of other behaviour in the underlying data may seem compelling, but cannot be shown to be statistically valid.

The claim that "volume is not going anywhere" in the last 10 years is not correct since it's been swinging pretty much over that period, going both up and down. An outlier in 2012 + few datapoints + system memory may well create what looks like a stall, but isn't.
because a thing is eloquently expressed it should not be taken to be as necessarily true
St. Augustine, Confessions V, 6

Stephan

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Re: Latest PIOMAS update (October 2019)
« Reply #3063 on: October 06, 2019, 09:14:53 AM »
I kindly ask you not to overestimate the effects of the nature of the trendlines. I experimented with linear, logarithmic and polynomial trendlines. In the end (e.g. "When will a certain dataset reach a certain value?") the differences are small, within a few percent or even less of error margin.

Jim Hunt

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Re: Latest PIOMAS update (October 2019)
« Reply #3064 on: October 06, 2019, 09:38:34 AM »
I would caution against calling any trendline "right" - it's only a model, an attempt to decipher underlying tendencies and predict future values.

The claim that "volume is not going anywhere" in the last 10 years is not correct since it's been swinging pretty much over that period, going both up and down. An outlier in 2012 + few datapoints + system memory may well create what looks like a stall, but isn't.

Axel Schweiger is one of the authors of this paper, referenced over at Judy's place:

https://doi.org/10.1038/s41561-018-0256-8

Quote
The relative contribution and physical drivers of internal variability in recent Arctic sea ice loss remain open questions, leaving up for debate whether global climate models used for climate projection lack sufficient sensitivity in the Arctic to climate forcing.

Here, through analysis of large ensembles of fully coupled climate model simulations with historical radiative forcing, we present an important internal mechanism arising from low-frequency Arctic atmospheric variability in models that can cause substantial summer sea ice melting in addition to that due to anthropogenic forcing. This simulated internal variability shows a strong similarity to the observed Arctic atmospheric change in the past 37 years.
Reality is merely an illusion, albeit a very persistent one - Albert Einstein

Wipneus

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Re: Latest PIOMAS update (October 2019)
« Reply #3065 on: October 06, 2019, 09:57:04 AM »
Continuing with the graphs...

Here is the updated Fram volume export graph. September export was below normal.

grixm

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Re: Latest PIOMAS update (October 2019)
« Reply #3066 on: October 06, 2019, 10:02:49 AM »
Did I mention that "I’m currently involved is a heated “debate” about Arctic sea ice trends over at ex Prof. Judy’s"?


Can you post the raw link? Archive.is doesn't work with 1.1.1.1 DNS servers.

Wipneus

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Re: Latest PIOMAS update (October 2019)
« Reply #3067 on: October 06, 2019, 10:07:36 AM »
The graphs updated with the annual minima.
Here is my collection of possible math fits to the timeline.

This graph was originally as a reply posted on the ASI blog. In those days the minima closely followed an exponential decline.
Not so in recent years. Every year the extrapolated day of zero ice is postponed about one year. Similar for most other mathematical functions. More about that in the next posts. 

A click will give you a slightly better image.

Wipneus

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Re: Latest PIOMAS update (October 2019)
« Reply #3068 on: October 06, 2019, 10:15:12 AM »
Here is the exponential fit. The 2019 minimum is above the trend, shifting the extrapolated zero ice after  2025 where with only data up to 2018 it was 2014.

Wipneus

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Re: Latest PIOMAS update (October 2019)
« Reply #3069 on: October 06, 2019, 10:24:20 AM »
Continuing discussion this, here is an attempt to show how the estimates of zero ice have been shifting. It is the same graph as in the previous post with extrapolations form former years added.
Here the dark blue line is the extrapolation using data up to 2018; The next greenish line data up to 2017
And so fort.
Many years the zero ice prediction was close to 2015 but that has been postponed, on average 1 year every year for the last 6 years or so.
 

Wipneus

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Re: Latest PIOMAS update (October 2019)
« Reply #3070 on: October 06, 2019, 10:29:10 AM »
Same as the previous but now a Gompertz regression, preferred by some. The Gompertz function approaches but never reaches zero, but still the same postponement to later and later dates is clear.

Wipneus

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Re: Latest PIOMAS update (October 2019)
« Reply #3071 on: October 06, 2019, 10:38:20 AM »
Finally a linear trend. The 2019 data point lies near perfect on the trend line. That means that the zero ice extrapolation has not shifted either and stays at 2032. That, and the fact that is has not changed much for many years gives some confidence to this date.

So for comparison I have added the same graph that I posted in 2012: also a 2032 zero ice extrapolation. The 'prediction' for 2019 is spot-on.

Wipneus

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Re: Latest PIOMAS update (October 2019)
« Reply #3072 on: October 06, 2019, 10:51:53 AM »
Finally the thickness map comparisons. Here are thickness map, compared with previous years and their diff's on the 10th of September (approximate day of annual minimum).

Pavel

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Re: Latest PIOMAS update (October 2019)
« Reply #3073 on: October 06, 2019, 11:02:36 AM »
Thanks for the update. It looks the Fram export was low in volume because the survived ice is very thin

Jim Hunt

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Re: Latest PIOMAS update (October 2019)
« Reply #3074 on: October 06, 2019, 11:28:28 AM »
Can you post the raw link?

I'm afraid not. Neven would have my guts for garters if I did that!

Perhaps you could employ the services of the Great God Google instead?

https://lmgtfy.com/?q=ex+prof+judy+sea+ice
« Last Edit: October 06, 2019, 11:34:25 AM by Jim Hunt »
Reality is merely an illusion, albeit a very persistent one - Albert Einstein

Jim Hunt

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Re: Latest PIOMAS update (October 2019)
« Reply #3075 on: October 06, 2019, 11:32:31 AM »
Finally a linear trend. The 2019 data point lies near perfect on the trend line.

The 'prediction' for 2019 is spot-on.

Thanks for all the assorted "extrapolations" Wipneus.

Please bear in mind that in conformance with what appears to be standard practice at ex Prof. Judy's my graph was for the PIOMAS monthly volume numbers for September, not the September daily minimum volume.
Reality is merely an illusion, albeit a very persistent one - Albert Einstein

binntho

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Re: Latest PIOMAS update (October 2019)
« Reply #3076 on: October 06, 2019, 11:48:59 AM »
Thanks as always for your postings Wipneus, and specifically for the extrapolation posts - it does seem that the humble linear prediction has the best track record so far, in spite of the apparently non-linear behaviour at times.
because a thing is eloquently expressed it should not be taken to be as necessarily true
St. Augustine, Confessions V, 6

Stephan

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Re: Latest PIOMAS update (October 2019)
« Reply #3077 on: October 06, 2019, 11:54:47 AM »
Continuing discussion this, here is an attempt to show how the estimates of zero ice have been shifting. It is the same graph as in the previous post with extrapolations form former years added.
Here the dark blue line is the extrapolation using data up to 2018; The next greenish line data up to 2017
And so fort.
Many years the zero ice prediction was close to 2015 but that has been postponed, on average 1 year every year for the last 6 years or so.
 
I visualised this shift in "time to zero dates" derived from this graph

El Cid

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Re: Latest PIOMAS update (October 2019)
« Reply #3078 on: October 06, 2019, 02:24:37 PM »
The trendline on this chart is obviously faulty.
The displayed linear trend was created using the Excel "TREND" function. Surely you don't want to start a "debate" with Microsoft too?

I will not debate excel functions. I debate their use (or even usefulness). I did take quite a few statistics classes and if 15 datapoints in a row are above your trendline than it is obvious that you should not use that trendline (whatever the type of the trend), because it is not that sort of trend. That is all I wanted to say. There are various methods to determine randomness in your residuals but you don't need any (other than your eyeballs) if a long string of datapoints are above or below the trendline. Any trendline.

With all that said, I also want to thank Wipneus for his great work. May we never see his trendlines hitting that zero point! :)

 

binntho

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Re: Latest PIOMAS update (October 2019)
« Reply #3079 on: October 06, 2019, 02:29:34 PM »
The trendline on this chart is obviously faulty.
The displayed linear trend was created using the Excel "TREND" function. Surely you don't want to start a "debate" with Microsoft too?
... and if 15 datapoints in a row are above your trendline than it is obvious that you should not use that trendline (whatever the type of the trend), because it is not that sort of trend.

It's not at all obvious.

Wipneus has showed that the linear trendline is the only one that has any validity - so are you saying that there is no trendline that can be used on this data?

System memory may well cause 15 datapoints to fall to one side and 15 to another, even if the underlying trend over 30 points is linear.
because a thing is eloquently expressed it should not be taken to be as necessarily true
St. Augustine, Confessions V, 6

dnem

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Re: Latest PIOMAS update (October 2019)
« Reply #3080 on: October 06, 2019, 02:51:41 PM »
The trendline on this chart is obviously faulty.
The displayed linear trend was created using the Excel "TREND" function. Surely you don't want to start a "debate" with Microsoft too?

I will not debate excel functions. I debate their use (or even usefulness). I did take quite a few statistics classes and if 15 datapoints in a row are above your trendline than it is obvious that you should not use that trendline (whatever the type of the trend), because it is not that sort of trend.
With all that said, I also want to thank Wipneus for his great work. May we never see his trendlines hitting that zero point! :)

Did they teach you that linear regression minimizes the sum of the SQUARE of the residuals? The raw count of residuals above/below the line is not a factor in fit.

Very useful stuff Wipneus and thank you for all your work.

El Cid

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Re: Latest PIOMAS update (October 2019)
« Reply #3081 on: October 06, 2019, 03:16:31 PM »
Wipneus has showed that the linear trendline is the only one that has any validity - so are you saying that there is no trendline that can be used on this data?

That is EXACTLY what I am saying. The linear trend is still the best of all the bad solutions (but that is just a coincidence because luckily we have data from 1979, which was almost the time when we started to lose ice seiously!!!) Had we started gathering data in 1950 or 60 or 70 it would all look very different...

I suspect it is so, because there are multiple trends. eg there was probably basically nontrending behaviour from 1950-1985 (CO2 growth counterbalanced by various aerosols), then a linear trend (loss of periphereal seas) until cca 2006-10, and now we have something else (I don't know what, but the Central Arctic seems different) until it changes again.


/last one on linear trends: the residuals should be a white noise, and there should be no autocorrelation, in our case it is clearly NOT a white noise/

 

blumenkraft

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Re: Latest PIOMAS update (October 2019)
« Reply #3082 on: October 06, 2019, 03:26:47 PM »
Wipneus has showed that the linear trendline is the only one that has any validity - so are you saying that there is no trendline that can be used on this data?
That is EXACTLY what I am saying.

+1
Refugees welcome

uniquorn

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Re: Latest PIOMAS update (October 2019)
« Reply #3083 on: October 06, 2019, 04:09:17 PM »
Thanks Wipneus. Here's an animation of the piomas thickness difference collage, feb-sep, for 2019

dnem

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Re: Latest PIOMAS update (October 2019)
« Reply #3084 on: October 06, 2019, 04:10:56 PM »
Last one on this. I totally agree with your last statement El Cid, including about autocorrelation. (But still, you don't just count positive and negative residuals!).

I have frequently railed here against curve fitting in such a rapidly changing environment and I will continue to do so!

philopek

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Re: Latest PIOMAS update (October 2019)
« Reply #3085 on: October 06, 2019, 04:46:53 PM »
The trendline on this chart is obviously faulty.
Summarizing: It is obviously statistically NOT a linear trend and even if it were the dataset used for them is probably not the right one.

The following is not meant personal but general and I only use the quoted post as an arbitrary trigger post.

My take on such discussions is that the trend is obviously downward and that's most probably the only thing that matters and is of interest.

Generally experts from various fields of expertise should stop to overshadow the relevant information with discussions about technical detail.

Ice cover is shrinking, ice thickness is shrinking, ice-volume is shrinking and that's all we have to focus on with the REAL goal to find ways to stop it or to slow it down significantly.

The later goal is difficult enough to achieve and even more difficult to take sufficient fellow humans with us onto that path.

All discussions about who has more insight and how exactly such a trend looks like is not target leading IMO or at least only as a sideshow.

Juan C. García

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Re: Latest PIOMAS update (October 2019)
« Reply #3086 on: October 06, 2019, 05:38:57 PM »
According to NSIDC, 2007 is still the second lowest on record. But if we look at JAXA, 2007 is the fourth lowest on record. So, if we still have AMSR2 data on the next decade, JAXA will put as the default graph, the years 2012, 2016 and 2019, but 2007 will be out.

More important, if we analyze the PIOMAS volume, 2007 is now the tenth lowest on record. September 2019 end up being less than 2/3 of the September 2007 volume (64.2%).

There has been critics that as a Forum, we have the tendency to forecast low values. It has been true in cases when there is a forecast of a blue ocean event, but from my point of view, not completely true if you look at volume.

It is true that the forecast of less than 1,000 km3 has been moving forward (from what we expected after September 2012) but we will still have the chance to see this figure (less than 1,000 km3) on the next decade. From my point of view, less than 2,000 km3 will be very bad and there is a greater chance that we have this figure on 2020-29.

Thank you, Wipneus! Great graphs!
« Last Edit: October 06, 2019, 05:54:52 PM by Juan C. García »
Which is the best answer to Sep-2012 ASI lost (compared to 1979-2000)?
50% [NSIDC Extent] or
73% [PIOMAS Volume]

Volume is harder to measure than extent, but 3-dimensional space is real, 2D's hide ~50% thickness gone.
-> IPCC/NSIDC trends [based on extent] underestimate the real speed of ASI lost.

oren

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Re: Latest PIOMAS update (October 2019)
« Reply #3087 on: October 06, 2019, 06:19:15 PM »
Thanks Wipneus. Here's an animation of the piomas thickness difference collage, feb-sep, for 2019
Wonderful animation.
Comparing with 2016 and 2012, this year had huge success in killing off initially positive anomalies in the Kara and Barents, and southern Laptev. Another big win was the Lincoln Sea, going from zero anomaly to terribly negative. OTOH, 2019 failed to kill off the last of the anomaly along the FJL-SVALBARD line, an area that is normally not hard to kill off, and lost its early big advantage on the Chukchi-Beaufort side. This was the main effect of the calm August.
Very interesting year.
Note: all win lose gain etc. should be in "". Not meant as good/bad.

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Re: Latest PIOMAS update (June 2019)
« Reply #3088 on: October 06, 2019, 07:48:01 PM »
PIOMAS Volume as at 30 September 2019  4.568  km3 '000
The standard graphs and tables as I use for the JAXA extent data are attached.

Volume loss in the first half of September mostly below average, gain in the 2nd half mostly above average.

But 2019 volume is still 2nd lowest in the satellite record, by 601 km3 (15%) ABOVE 2012, and 221 k (5%) below 2011 the 3rd lowest, and less than 2018 by 549 km3 (11%).


_______________________________________________________________
The last table is a look at projections to the next maximum. Far too early to take it seriously, although it is obvious that 2012-13 disappears from the minimum maximum possibilities, replaced by 2016-17.

2012 shown again to be an outlier
Graph vol-4 shows the impressive decadal loss trend
« Last Edit: October 06, 2019, 08:18:33 PM by gerontocrat »
"Para a Causa do Povo a Luta Continua!"
"And that's all I'm going to say about that". Forrest Gump
"Damn, I wanted to see what happened next" (Epitaph)

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Re: Latest PIOMAS update (October 2019)
« Reply #3089 on: October 06, 2019, 07:56:03 PM »
Just for interest here is the plume of projections for October. Will the current slow refreeze of area and extent be reflected in volume data?

Also shown is how 2012 did produce a new record 365 day average volume low but not so impressive compared with 2016-17. 365 day data is currently progressing to a new record low - perhaps by the end of 2021 .

An just a reminder of how the 2019 minimum was at a record low by the normal amount if 2012 is excluded or averaged with the bounce back the following year.
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crandles

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Re: Latest PIOMAS update (October 2019)
« Reply #3090 on: October 06, 2019, 09:08:32 PM »
I have to admit the linear trend is surprisingly stable over last several years. I was surprised by this. 4 parameter gompertz fits can only manage such consistency since 2014.

To me a question remains of whether the trend in the data from 2012 to 2019 being pretty much an extension of the prior linear trend is just coincidence having wandered in different directions as indicated by the residuals being too similar.

Alternately perhaps autocorrelation explains the persistent residuals and the linear trend is more reliable than using too many parameters.

Either view seems quite reasonable as far as I can tell. I tend to prefer to give the shape models suggest more weight. Tamino finding statistically significant slow down in extent decline also improved my confidence in some form of sigmoid shape. But Wipneus has made me stop and think maybe this isn't yet enough to consider it done and dusted.


Archimid

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Re: Latest PIOMAS update (October 2019)
« Reply #3091 on: October 06, 2019, 10:20:00 PM »
I like using both the maximum and the minimum to glimpse into the future of the ice. Attached is an animation using the intersection of the trendlines of maximum volume and volume loss from 2007 to 2019.  Date of intersection estimated by sight, but it shouldn't be off by more than 1 year.

2032 has indeed been remarkably stable.
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binntho

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Re: Latest PIOMAS update (October 2019)
« Reply #3092 on: October 07, 2019, 07:16:46 AM »
I don't think there are any true linear rates of change in nature. Many systems will in isolation exhibit polynomial rates of change, but linear? I can't think of a single instance.

Expecting complex and compound systems to exhibit any behaviour that can be expressed in a single mathematical formula (linear, polynomial or other) is probably pure wishful thinking. Which means that every and all attempts at extracting trends from data are "wrong" in that they will never be able to express what the system is really doing.

For any and all real-world data, finding the "least bad" option is the best we can do. And I think we have seen enough examples over the last couple of days to lay this to rest once and for all: The least-bad modelling option of past satellite-era behaviour of arctic sea ice is by far the linear one. And at the same time, it may well be the worst option for predicting future behaviour - we'll just have to wait and see!
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Jim Hunt

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Re: Latest PIOMAS update (October 2019)
« Reply #3093 on: October 07, 2019, 09:09:48 AM »
Expecting complex and compound systems to exhibit any behaviour that can be expressed in a single mathematical formula (linear, polynomial or other) is probably pure wishful thinking.

I've been extolling the virtues of "The Slow Transition" concept over at Judy's, where my words of wisdom haven't fallen on entirely deaf ears!

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Shared Humanity

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Re: Latest PIOMAS update (October 2019)
« Reply #3094 on: October 07, 2019, 04:39:48 PM »
I've been extolling the virtues of "The Slow Transition" concept over at Judy's, where my words of wisdom haven't fallen on entirely deaf ears!

While this is based solely on my reading the work of others here, I also think the slow transition concept has merit.

kaixo

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Re: Latest PIOMAS update (October 2019)
« Reply #3095 on: October 08, 2019, 04:18:19 PM »
I like using both the maximum and the minimum to glimpse into the future of the ice. Attached is an animation using the intersection of the trendlines of maximum volume and volume loss from 2007 to 2019.  Date of intersection estimated by sight, but it shouldn't be off by more than 1 year.

2032 has indeed been remarkably stable.

This way of estimating the trendline of the september volume minimum at least includes the two basic processes determining it, freezing and melting.

To get into this a little bit more, it could be interesting to estimate the trendlines in decadal montly volume averages. To me Jim Pettits Arctic death spiral graph http://iwantsomeproof.com/extimg/siv_annual_polar_graph.png
suggests that over the last 40 years the trendlines in decadal average monthly volumes are different in winter months to those in summer/autumn.

I am aware that with four decades of measurements you only have four data points for each month, which makes any result from this exercise untrustworthy. Still, the arctic death spiral graph consists of quite a few individual months and the shape suggests a rather smooth change over the months of the year and over the years. And the 'dent' in the graph in recent years from august-october i find especially intruiging. To me it suggests some sort of change in dynamics.

Maybe one could use 5 yearly averages and thus create 8 data points for each month. Anyway, maybe like this one could estimate the decadal (or 5-yearly) monthly averages all year around for the near future.

Does anyone know where to find the monthly volume data since 1979? Maybe i will give it a try in a few months time when we also have 2019 numbers, although i haven't had anything to do with statistics for 30 years, so it will be quite a challenge  :)  If you have any suggestions or think this is a waste of time because of a lack of data or other reasons, let me know.


« Last Edit: October 08, 2019, 06:19:56 PM by kaixo »

Jim Hunt

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Re: Latest PIOMAS update (October 2019)
« Reply #3097 on: October 08, 2019, 06:46:16 PM »
WOW, kudos to Apple. I could copy&paste this into a blank Numbers sheet and it converted it to .CSV just like that.

This is 1979 vs. 2019
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Juan C. García

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Re: Latest PIOMAS update (October 2019)
« Reply #3098 on: October 08, 2019, 07:33:57 PM »
The always great video of Arctic Sea Ice Minimum Volumes 1979-2019, by Andy Lee Robinson:

Which is the best answer to Sep-2012 ASI lost (compared to 1979-2000)?
50% [NSIDC Extent] or
73% [PIOMAS Volume]

Volume is harder to measure than extent, but 3-dimensional space is real, 2D's hide ~50% thickness gone.
-> IPCC/NSIDC trends [based on extent] underestimate the real speed of ASI lost.

Neven

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Re: Latest PIOMAS update (October 2019)
« Reply #3099 on: October 14, 2019, 05:35:11 PM »
Latest update on the ASIB: PIOMAS October 2019
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