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What will the NSIDC 2018 Arctic SIE September average be?

Between 5.0 and 5.5 million km2
1 (1.3%)
Between 4.75 and 5.25 million km2
1 (1.3%)
Between 4.5 and 5.0 million km2
10 (13%)
Between 4.25 and 4.75 million km2
20 (26%)
Between 4.0 and 4.5 million km2
11 (14.3%)
Between 3.75 and 4.25 million km2
8 (10.4%)
Between 3.5 and 4.0 million km2
3 (3.9%)
Between 3.25 and 3.75 million km2
5 (6.5%)
Between 3.0 and 3.5 million km2
6 (7.8%)
Between 2.75 and 3.25 million km2
3 (3.9%)
Between 2.5 and 3.0 million km2
1 (1.3%)
Between 2.25 and 2.75 million km2
0 (0%)
Between 2.0 and 2.5 million km2
2 (2.6%)
Between 1.75 and 2.25 million km2
0 (0%)
Between 1.5 and 2.0 million km2
0 (0%)
Between 1.25 and 1.75 million km2
0 (0%)
Between 1.0 and 1.5 million km2
1 (1.3%)
Between 0.75 and 1.25 million km2
1 (1.3%)
Between 0.5 and 1.0 million km2
2 (2.6%)
Between 0.25 and 0.75 million km2
0 (0%)
Between 0 and 0.5 million km2
2 (2.6%)

Total Members Voted: 76

Voting closed: June 13, 2018, 12:10:19 AM

Author Topic: NSIDC 2018 Arctic SIE September average: June poll  (Read 3268 times)

Neven

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NSIDC 2018 Arctic SIE September average: June poll
« on: June 06, 2018, 12:10:19 AM »
ATTENTION: There are two polls on the ASIF. This one is for NSIDC sea ice extent monthly minimum or September average (which is also used for the SIPN sea ice outlook), the other is for JAXA sea ice extent daily minimum (provided by ADS, previously by IJIS). Make sure you are aware of the difference before voting. You can discuss various extent/area data sets in this dedicated thread.

-----

This NSIDC extent poll will run for 7 days (until June 12th). Until then you can change your vote. There will be a new poll next month.

Here's how things are currently looking based on data up to June 4th:



These are the September averages for the last 13 years (in millions km2, found here):

    2005: 5.50
    2006: 5.86
    2007: 4.27
    2008: 4.69
    2009: 5.26
    2010: 4.87
    2011: 4.56
    2012: 3.57
    2013: 5.21
    2014: 5.22
    2015: 4.62
    2016: 4.51
    2017: 4.80

You can use the comment thread below to motivate your choice, but discuss various SIE/SIA data sets in this dedicated thread.
« Last Edit: June 06, 2018, 12:41:38 AM by Neven »
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Neven

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Re: NSIDC 2018 Arctic SIE September average: June poll
« Reply #1 on: June 06, 2018, 12:42:17 AM »
Sorry for not opening the thread earlier, I was a bit busy.

Is everyone seeing the graph okay?

PS I voted 'Between 3.75 and 4.25 million km2'.
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RikW

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Re: NSIDC 2018 Arctic SIE September average: June poll
« Reply #2 on: June 06, 2018, 09:05:21 AM »
I can see it. Seeing the current weather forecasts I fear this year will see a lot of new records. I voted for 3-3.5 but in most polls I'm too negative ;)

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Re: NSIDC 2018 Arctic SIE September average: June poll
« Reply #3 on: June 06, 2018, 02:08:37 PM »
4.25 - 4.75 m km2 but lets see how June plays out

Jim Pettit

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Re: NSIDC 2018 Arctic SIE September average: June poll
« Reply #4 on: June 07, 2018, 12:35:27 PM »
For the record, were the remainder of the melt season to follow the average daily decrease of the last ten years, average NSIDC extent for September would end up at 4.228M km2.

CLICK FOR FULL-SIZE IMAGE:


FWIW, following 2012's trajectory would result in a September average of 2.826 M km2.

Tealight

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Re: NSIDC 2018 Arctic SIE September average: June poll
« Reply #5 on: June 07, 2018, 01:56:46 PM »
I forecast 4.30 million km2.

Volume, Temperature, Area/Extent are 2nd place, but sea ice compaction is in last place. It looks like another edge melting season and not a melt pond season.

Neven can't you make one category for below 2 million? For extent even 2 million is pretty much impossible this year. 0 km2 will never be reached simply due to the coastline sensor noise adding several thousand km2.

Neven

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Re: NSIDC 2018 Arctic SIE September average: June poll
« Reply #6 on: June 07, 2018, 03:03:20 PM »
Neven can't you make one category for below 2 million? For extent even 2 million is pretty much impossible this year. 0 km2 will never be reached simply due to the coastline sensor noise adding several thousand km2.

I believe this was discussed a couple of years ago when we did the first polls. I can't remember why, but we decided that it was better to have bins all the way down to zero. Probably because it makes it easier to calculate the average and median, etc.
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crandles

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Re: NSIDC 2018 Arctic SIE September average: June poll
« Reply #7 on: June 07, 2018, 05:57:52 PM »

These are the September averages for the last 13 years (in millions km2, found here):

    2005: 5.50

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Hyperion

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Re: NSIDC 2018 Arctic SIE September average: June poll
« Reply #8 on: June 07, 2018, 07:31:08 PM »
I forecast 4.30 million km2.

Volume, Temperature, Area/Extent are 2nd place, but sea ice compaction is in last place. It looks like another edge melting season and not a melt pond season.

Neven can't you make one category for below 2 million? For extent even 2 million is pretty much impossible this year.
It may not be that melt pondy but as there is now not enough deep keeled ice dispersed around the basin to keep a viable chilled lens deep enough to keep the surface mixing from entraining the massive amount of heat starting about 40m depth, AND now often only 1psu saltier, I think bottom melt is going to make less than 2 million very possible this year. And low compaction will assist this.
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Stephan

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Re: NSIDC 2018 Arctic SIE September average: June poll
« Reply #9 on: June 07, 2018, 07:42:28 PM »
I expect for the medium September extent something slightly below 5 mio. km². I do not expect a near-record value, the ice is thicker than last year, at least in a huge area of the CAB.
Let's look how it'll all end in the end. I am looking for knowing it in the first week of October...

Tetra

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Re: NSIDC 2018 Arctic SIE September average: June poll
« Reply #10 on: June 07, 2018, 09:01:53 PM »
3.75-4.25

I know I don’t post herw very often and lurk a lot, but I feel motivated too as it seems this melting season is finally getting interesting! Although we’ll have a much better idea of the minimum by the rnd of June it seems, after we can gauge the metling momentum thanks to melt ponding etc.

Something about this year reminds of 2016 for some reason. Althoigh the ice is thicker, it’s thicker in all the wrong places and thinner in even worse places.

Therefore I think top 3 is a real possibility. With a new record a more distant prospect.

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Re: NSIDC 2018 Arctic SIE September average: June poll
« Reply #11 on: June 11, 2018, 06:20:09 PM »
4.5-5 based on a crude statistical method:

latest 5-year averages

2007-2011: 4,78   
2008-2012: 4,65   
2009-2013: 4,78   
2010-2014: 4,76   
2011-2015: 4,70   
2012-2016: 4,63
2013-2017: 4,87

Quite a few individual years have of course been out of the 4.5-5 range, but considering the time of year this must do for now. Next month I propably change to the let's see what Slater team predicts method, which turned out to be succesful last year. (If I don't remember wrong they have had quite a good record on other years too...) But of course many a thing can happen between now and September :)

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Re: NSIDC 2018 Arctic SIE September average: June poll
« Reply #12 on: June 12, 2018, 04:30:30 AM »
3.75-4.25.

I simply went one bin - 0.25 - above my prediction for the daily minimum that I explained here.
« Last Edit: June 12, 2018, 04:41:26 AM by slow wing »

Daniel B.

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Re: NSIDC 2018 Arctic SIE September average: June poll
« Reply #13 on: June 12, 2018, 02:21:07 PM »
4.5-5 based on a crude statistical method:

latest 5-year averages

2007-2011: 4,78   
2008-2012: 4,65   
2009-2013: 4,78   
2010-2014: 4,76   
2011-2015: 4,70   
2012-2016: 4,63
2013-2017: 4,87

Quite a few individual years have of course been out of the 4.5-5 range, but considering the time of year this must do for now. Next month I propably change to the let's see what Slater team predicts method, which turned out to be succesful last year. (If I don't remember wrong they have had quite a good record on other years too...) But of course many a thing can happen between now and September :)

I did something similar, and came up with the same range.  The sea ice this year has been tracking 2015 fairly closely for the past three months, so I look to sea a similar minimum.  This would be at the low end of the bin, so I may lower my vote one notch.

Steven

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Re: NSIDC 2018 Arctic SIE September average: June poll
« Reply #14 on: June 14, 2018, 09:38:15 PM »
The poll is closed.  People voted relatively high this year, compared to the votes in the June polls of the past 5 years:





The fluo-green bins correspond to the observed NSIDC September extent in the past 5 years.

The median of the votes in the June 2018 poll is about 4.21 million km2

For comparison, the median of the votes was about 3.32 (million km2) in the June 2013 poll,  4.04 in the June 2014 poll,  4.02 in the 2015 poll,  3.82 in the 2016 poll, and 3.44 in the 2017 poll.

(Note about the above graphic: the 2018 poll has overlapping bins of width 0.5 million km2.  To compare it with the polls in previous years, I split each of the overlapping bins in two equal halves of width 0.25 million km2 and distributed the votes in the bin evenly over its two halves.)

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Re: NSIDC 2018 Arctic SIE September average: June poll
« Reply #15 on: June 15, 2018, 02:56:57 AM »
Thanks, Steven.  That's interesting.  This past year there's been more explicit discussion of the accuracy (or lack thereof)  of previous poll predictions.  Maybe that's having an effect on how people vote.

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Re: NSIDC 2018 Arctic SIE September average: June poll
« Reply #16 on: June 15, 2018, 05:40:05 AM »
How accurate should the predictions be?

By far the worst prediction was the first year, 2013, when the median was 3.32 and the melt season ended at 5.21 so off by 1.89.

Was the forum particularly alarmist in 2013? Or did it instead have something to do with the trend of preceding seasons, dropping from 4.56 in 2011 to 3.57 in 2012 - a drop of 0.99.

So the median prediction, after a drop of 0.99 in 2012, was to drop only a further 0.25 in 2013.

Imo that was not so unreasonable given the information available - and yet it was the worst prediction. Imo that was Nature's fault more than the fault of the participants in the poll.

If someone wants to make a counter-argument that it was the participants fault then they would do well to explain how the 5.21 result could have been known in advance in 2013, or at least a good approximation to that. Good luck!

So imo it's not a case of having been chastened out of alarmist tendencies. Instead, the main reason we didn't, this year, pick as low as in 2013 is the additional physical information available to us from the intervening years.

We still might anyway be off by a lot this year - Nature simply isn't that easy to predict here!
« Last Edit: June 15, 2018, 05:46:18 AM by slow wing »

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Re: NSIDC 2018 Arctic SIE September average: June poll
« Reply #17 on: June 15, 2018, 07:19:48 AM »
Not sure how much credence the DMI modeled ice thickness is, but based on that I predict this year will not see a record melt. Had I voted, I would have predicted 4.75 to 5.25 km2.
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Re: NSIDC 2018 Arctic SIE September average: June poll
« Reply #18 on: June 15, 2018, 02:48:06 PM »
Quote
So the median prediction, after a drop of 0.99 in 2012, was to drop only a further 0.25 in 2013.

In a chaotic system, I think after such a large drop it would be unusual to expect a further drop from the new low the following year, and that the principle of "regression to the mean" would mean that you should expect an increase the following year.

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Re: NSIDC 2018 Arctic SIE September average: June poll
« Reply #19 on: June 15, 2018, 03:56:20 PM »
How accurate should the predictions be?

By far the worst prediction was the first year, 2013, when the median was 3.32 and the melt season ended at 5.21 so off by 1.89.

Was the forum particularly alarmist in 2013? Or did it instead have something to do with the trend of preceding seasons, dropping from 4.56 in 2011 to 3.57 in 2012 - a drop of 0.99.

So the median prediction, after a drop of 0.99 in 2012, was to drop only a further 0.25 in 2013.

Imo that was not so unreasonable given the information available - and yet it was the worst prediction. Imo that was Nature's fault more than the fault of the participants in the poll.

If someone wants to make a counter-argument that it was the participants fault then they would do well to explain how the 5.21 result could have been known in advance in 2013, or at least a good approximation to that. Good luck!

So imo it's not a case of having been chastened out of alarmist tendencies. Instead, the main reason we didn't, this year, pick as low as in 2013 is the additional physical information available to us from the intervening years.

We still might anyway be off by a lot this year - Nature simply isn't that easy to predict here!

Whether being out by 1.89 is a bad result or not, depends in the confidence limits put on the prediction. If you had confidence limits of 0.1, then its really awful to be out by 1.89, and if you had confidence limits of 2.0 it isn't.

I don't think the median is a good measure for judging poll accuracy. I think there are three different populations represented in the poll, and only one of them is interested in how close their guess is (the others being only concerned about whether its a record or not, and whether its a blue ocean or not). This shows up as a multi-modal distribution and I'd take the highest mode as the indicator of where those who are interested in accuracy are making predictions.

In the case of 2013 this mode is 7 bins away from the outcome, which my challenge would score at -10, -6, -4, -2 and 0, depending on expressed confidence.

In the case of 2014 and 2017 this mode is 5 bins away from the outcome, for scores of -10, -6, -4 , -1 and 0.

In 2015 and 2016 its just 2 bins out for scores of -10, -2, 1, 1, 0.

Note that I am taking the mode by eye off Steven's post above and several of those years might well be judged a bin closer if the original data was used and it was in the same format as this years polls.

Overall, I score having very high confidence in the forum poll -50, high confidence -22, medium confidence -10, low confidence -2 and no confidence 0. It would seem Neven's lack of confidence in his entry has something to recommend it.  ;)

The 2013 polling was heavily influenced by looking at an exponential trend. Those that voted based on extrapolating an exponential trend should have been aware that these extrapolations have very high error margins and put a wide margin of confidence on their prediction. I think 3.5 was tenable in the June 2013 poll, but ruling out 5.2 wasn't, and 3.5 was no longer tenable by July 2013.

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Re: NSIDC 2018 Arctic SIE September average: June poll
« Reply #20 on: June 16, 2018, 01:09:00 AM »
I can't help but wonder what a June 1st poll would have said about 2012. I bet very few voters would have aimed as low as it actually scored, given the extent on that date was nothing special at all. My point being that the next record or even BOE will probably not be immediately recognized as such.

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Re: NSIDC 2018 Arctic SIE September average: June poll
« Reply #21 on: June 16, 2018, 01:34:59 AM »
The poll is closed.  People voted relatively high this year, compared to the votes in the June polls of the past 5 years:

I am a lurker the last few months, but one who uses past data to make future predictions I am surprised just how biased the community is. There is so much good science to read about here, but the leaning is strongly alarmist, based on these very clear results. There is a risk that this attitude could also bias the science if not careful.

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Re: NSIDC 2018 Arctic SIE September average: June poll
« Reply #22 on: June 16, 2018, 06:25:12 AM »
The poll is closed.  People voted relatively high this year, compared to the votes in the June polls of the past 5 years:

I am a lurker the last few months, but one who uses past data to make future predictions I am surprised just how biased the community is. There is so much good science to read about here, but the leaning is strongly alarmist, based on these very clear results. There is a risk that this attitude could also bias the science if not careful.
Considering current weather conditions, ice quality and melt pond fraction in the Arctic, I think most of the predictions are pretty conservative and possibly too high.

I used to use the trend and year over year data to make my estimates.  2013 & 14 smacked me in the face over that. 

More and more I'm trying to get a sense of weather trends and oceanic heat import, as we're seeing on unprecedented levels on both sides of the Arctic.

It all hinges on the weather, and so far, extent numbers notwithstanding, it hasn't been favorable for retention.
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Steven

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Re: NSIDC 2018 Arctic SIE September average: June poll
« Reply #23 on: June 16, 2018, 10:17:48 PM »
I can't help but wonder what a June 1st poll would have said about 2012. I bet very few voters would have aimed as low as it actually scored, given the extent on that date was nothing special at all.

By mid-June 2012 it was clear that there was strong surface melting and melt ponding going on.  It affected the sea ice concentration maps and the sea ice area numbers.

This forum started in 2013, but I found some older polls in the archives of Neven's blog, e.g. for June 2012, July 2012.  Those polls had a different format than on this forum, so it's a bit tricky to compare.  Anyway, for the June 2012 poll for NSIDC September extent, the median of the votes was about 4.22 million km2.  The actual value that year was 3.61 million km2, so the poll median was too conservative by about 0.6 million km2.

Note that NSIDC revised its methodology last year: they are now calculating the monthly average extent in a different way than before.  They also revised the numbers for previous years, which are now slightly lower than the original numbers (see table below), but I think it's more fair to use the original values to judge the accuracy of previous years' polls.


                    2012  2013  2014  2015  2016  2017
NSIDC v2:     3.61   5.35   5.29   4.68   4.72   4.87
NSIDC v3:     3.57   5.21   5.22   4.62   4.51   4.80

June median:4.22   3.32   4.04   4.02   3.82   3.44

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Re: NSIDC 2018 Arctic SIE September average: June poll
« Reply #24 on: June 28, 2018, 01:59:38 AM »
I think most of the predictions are pretty conservative and possibly too high.

Considering that the solar TSI has been low for 11+ years (including a 3+ year period setting a 100 year record), more efforts will have to be made to show that fairly large predictions of Arctic sea ice increases ARE too high. If lower solar TSI has "bottomed out", continued CO2 emissions should continue Earth warming trends. If solar TSI increases to "normal" levels, long term global CO2 warming levels will leap. 

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Re: NSIDC 2018 Arctic SIE September average: June poll
« Reply #25 on: June 28, 2018, 03:51:25 PM »
I think most of the predictions are pretty conservative and possibly too high.


Considering that 23% of the voters predict a new low (including a few predicting ice-free conditions) and another 21% predict second lowest, I would state that they are more likely too low.  75 out of 77 votes predicted a September average below the average extent of the past five years.  That leaves 2 votes out of 77 that are higher than the average, and none higher that the highest September average of the past five years.  Not exactly what I would call conservative predictions.

Neven

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Re: NSIDC 2018 Arctic SIE September average: June poll
« Reply #26 on: June 28, 2018, 03:54:18 PM »
But they're pretty conservative, with the ASIF's track record in mind.  ;) ;D
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Re: NSIDC 2018 Arctic SIE September average: June poll
« Reply #27 on: June 28, 2018, 07:42:22 PM »
75 out of 77 votes predicted a September average below the average extent of the past five years.

Seems true, seems noteworthy enough. But it also feels cherrypicked.

So what's that stat if you use the last 6 years instead of the last 5 years? (65-12)
last 10 years? (~70-7)
13 years? (75-2)

last 3 years? (65-12)

Less dramatic, but still striking.

Daniel B.

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Re: NSIDC 2018 Arctic SIE September average: June poll
« Reply #28 on: June 28, 2018, 08:23:09 PM »
75 out of 77 votes predicted a September average below the average extent of the past five years.

Seems true, seems noteworthy enough. But it also feels cherrypicked.

So what's that stat if you use the last 6 years instead of the last 5 years? (65-12)
last 10 years? (~70-7)
13 years? (75-2)

last 3 years? (65-12)

Less dramatic, but still striking.

Whether we choose the highest (75-2) or lowest (65-12), the predictions are skewed towards the low end, not the high.  If it were reversed, then I might say the guesses are conservative and possibly too high.