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petm

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Re: Slater's thread
« Reply #100 on: August 02, 2019, 06:21:46 PM »
As a native English speaker, I don't agree that 'predict' necessarily implies subjectivity. It depends on the context. I do agree that 'predict' is more forceful than 'forecast'.

blumenkraft

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Re: Slater's thread
« Reply #101 on: August 02, 2019, 06:30:04 PM »
Thanks, Petm. That helps. :)
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Re: Slater's thread
« Reply #102 on: August 02, 2019, 08:23:20 PM »
Discussing the semantics of the words "forecasting" and "prediction" is drifting dangerously close to being off-topic, so I will only comment on this once.

As with all models, do they ever predict anything?
No. They estimate, they calculate probabilities, they take knowns into account and they are unaware of black swans; and that's it.
Indeed. We aim to get a model that somehow reflects the thing we are modelling, and hence we can interpret the numbers we get out in some useful way. The interpretation and presentation of the output of models can sometimes be as hard as writing the model in the first place.

Quote
You can make true claims about the future. And those are the ones that would fall in the category of predictions.

Sorry for being pedantic here, but is my understanding of the word wrong?
The problem isn't that your understanding of the word is wrong: the problem is that there isn't a clear, precise, scientific definition of the words "prediction" and "forecast". It will vary from one discipline to another (and even within the same discipline). And then we've got "normal" day-to-day use of the words. Largely, they are interchangeable in English - although, stylistically, one often works better than the other.

In common parlance, "forecast" sounds more scientific than "prediction": hence we watch "Weather Forecasts" on the news, not "Weather Predictions", and a crystal-ball gazer makes "predictions" about the future (which are mostly wrong), not "forecasts". But... it would be perfectly acceptable to say that "Model X predicts Y": as per "Einstein's General Theory of Relativity predicts a gravitational lens effect of 0.0001 degrees". "Forecast", in this case, would just sound wrong (to me, anyway).

Personally, I don't think there is a lot of point getting hung-up on the use of those words. I'll go with whatever people feel most comfortable with - or I'll just try to avoid using the words and write math(s) instead :)
"There are two ways of constructing a software design: One way is to make it so simple that there are obviously no deficiencies, and the other way is to make it so complicated that there are no obvious deficiencies. The first method is far more difficult." -- C.A.R. Hoare

blumenkraft

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Re: Slater's thread
« Reply #103 on: August 02, 2019, 08:32:06 PM »
hence we watch "Weather Forecasts" on the news, not "Weather Predictions", and a crystal-ball gazer makes "predictions" about the future (which are mostly wrong), not "forecasts".

Very good point. Thanks for your answer. :)

I don't think though this is awfully off-topic? Making clear what we are talking about, defining words is helpful for this thread.
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petm

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Re: Slater's thread
« Reply #104 on: August 02, 2019, 09:31:04 PM »
Personally I don't think we need to worry too much about staying always and exactly on topic, on threads such as this one. That's mainly a problem on the melting thread (and others that are highly read).

GlassHalfEmpty

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Re: Slater's thread
« Reply #105 on: August 02, 2019, 10:01:19 PM »
Very good point. Thanks for your answer. :)
It's a pleasure :)

Quote
I don't think though this is awfully off-topic? Making clear what we are talking about, defining words is helpful for this thread.
I think my point is that that in informal English, they are used almost interchangeably, and in technical stuff, there isn't a very good definition for these particular words. Basically, I'm saying: don't read too much in to the use of the word "forecast" or "prediction" - just treat them the same way.

I doubt that anybody who uses the words (including me) intends them to be describing different concepts. I'm happy to be corrected on that.

Back on topic:

Does anybody know if there is an archive of the Slater model daily predictions/forecasts? And if so, where? Or any links to a description of the model's methodology. I've tried googling the obvious, but not found any paper whose title screams at me "this is it". I might just have been a bit dumb.

(Anyway, having popped up after so long lurking, I'll be away from the forums for a couple of weeks.)
"There are two ways of constructing a software design: One way is to make it so simple that there are obviously no deficiencies, and the other way is to make it so complicated that there are no obvious deficiencies. The first method is far more difficult." -- C.A.R. Hoare

petm

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Re: Slater's thread
« Reply #106 on: August 02, 2019, 11:02:55 PM »
Does anybody know if there is an archive of the Slater model daily predictions/forecasts? And if so, where? Or any links to a description of the model's methodology.

No archive that I'm aware of. I started saving them a few weeks ago.

The only methodology I could find was here: http://cires1.colorado.edu/~aslater/SEAICE/
Click 'About the plots' and then poster. I get the impression he was thinking of publishing it at one point but it didn't pan out for whatever reason.

binntho

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Re: Slater's thread
« Reply #107 on: August 02, 2019, 11:50:25 PM »
Well, that's the thing. I can predict this pencil will fall, 100% of the time. It will always work, even in the future.
Reminds me of the guy who would alway bet on the coin landing edge up - but seriously, saying what will happen based on 100% knowledge of the outcome is not predicting.
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Or when Einstein thought about relativity and was able to predict gravitational lenses. And by doing so, he proved his theory to be correct. He made the claim, that you can see stars behind the sun during a solar eclipse.
And scarily so. The ability of mathematics and mathematical formulas to predict real-world behaviour has some physical theorists reaching for the whisky glass.
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You can make true claims about the future. And those are the ones that would fall in the category of predictions.
No, you cannot make "true claims about the future". There is no such thing. You can predict what you think will happen and then you can be proven right or wrong.

And lots of predictions are totally off, totally wrong. When the Internet first became a thing, I was one of those optimistic techies who started an Internet Access Provider. Practically all my predictions at the time turned out to be totally wrong, including the financial viability of running an IAP.

But the predictions that I and others were making about what the Internet would be used for, and what it was good for, also turned out to be so very very wrong (except for the porn, of course.)
because a thing is eloquently expressed it should not be taken to be as necessarily true
St. Augustine, Confessions V, 6

petm

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Re: Slater's thread
« Reply #108 on: August 03, 2019, 12:11:42 AM »
Quote
Det er vanskeligt at spaa, især naar det gælder Fremtiden.

It is difficult to make predictions, especially about the future. (English translation)

https://quoteinvestigator.com/2013/10/20/no-predict/

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Re: Slater's thread
« Reply #109 on: August 03, 2019, 06:42:10 AM »
No, you cannot make "true claims about the future". There is no such thing. You can predict what you think will happen and then you can be proven right or wrong.

Erm, what? How is "the pencil will fall when i tip it over" not a "true claim about the future"?
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binntho

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Re: Slater's thread
« Reply #110 on: August 03, 2019, 07:14:54 AM »
No, you cannot make "true claims about the future". There is no such thing. You can predict what you think will happen and then you can be proven right or wrong.

Erm, what? How is "the pencil will fall when i tip it over" not a "true claim about the future"?
Boolan logic only allows present tense. I can make a claim that will become true when the pencil falls. But the claim is not true until the pencil has fallen. Truth does not apply to future events.

Epistemiologically the whole concept of truth is of course much more complicated than Boolean logic would imply. But if we want to talk science and statistics, truth becomes a much better defined concept, as laid down by Boole.
because a thing is eloquently expressed it should not be taken to be as necessarily true
St. Augustine, Confessions V, 6

blumenkraft

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Re: Slater's thread
« Reply #111 on: August 03, 2019, 07:21:10 AM »
Boolan logic/Epistemiologically

Fancy words. Not convincing though.
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binntho

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Re: Slater's thread
« Reply #112 on: August 03, 2019, 07:38:26 AM »
Boolan logic/Epistemiologically

Fancy words. Not convincing though.
Well, words are just words. And "truth" only exists in the present.

Predictions are not true in any sense of the word, but they can become true. When you "predict" an outcome with so close to 100% certainty that you could stake your life on it, then it is not a prediction.

So Einstein made predictions that became true, but he did not make true predictions.
because a thing is eloquently expressed it should not be taken to be as necessarily true
St. Augustine, Confessions V, 6

El Cid

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Re: Slater's thread
« Reply #113 on: August 03, 2019, 08:14:59 AM »
is this still slater's thread?!

 :o

DrTskoul

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Re: Slater's thread
« Reply #114 on: August 03, 2019, 09:17:22 AM »
What do you mean by "Slater" and what by "thread" ???   :o :o

be cause

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Re: Slater's thread
« Reply #115 on: August 03, 2019, 10:01:14 AM »
Slaters often get trapped in my sink . I leave a thread for them to use as a ladder .. b.c.
2007 + 5 = 2012 + 4 = 2016 + 3 = 2019 ...

binntho

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Re: Slater's thread
« Reply #116 on: August 03, 2019, 10:48:07 AM »
Slaters often get trapped in my sink . I leave a thread for them to use as a ladder .. b.c.
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because a thing is eloquently expressed it should not be taken to be as necessarily true
St. Augustine, Confessions V, 6

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Re: Slater's thread
« Reply #117 on: August 06, 2019, 06:03:32 AM »
No, you cannot make "true claims about the future". There is no such thing. You can predict what you think will happen and then you can be proven right or wrong.

Erm, what? How is "the pencil will fall when i tip it over" not a "true claim about the future"?
Because I might grab it before it falls, or some other unlikely event may occur. The claim is highly likely by not certain!
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binntho

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Re: Slater's thread
« Reply #118 on: August 06, 2019, 06:14:41 AM »
No, you cannot make "true claims about the future". There is no such thing. You can predict what you think will happen and then you can be proven right or wrong.

Erm, what? How is "the pencil will fall when i tip it over" not a "true claim about the future"?
Because I might grab it before it falls, or some other unlikely event may occur. The claim is highly likely by not certain!
As David says. Claims about the future cannot be true, although they can have a likelihood tending very strongly towards 100%. The claim "the sun will rise tomorrow" cannot be said to be true, although the changes of it not happening are miniscule.

In mathematics and formal logic, truth is very strictly defined.

In daily usage, truth is usually restricted to claims about the external world, usually in the present tense, rarely in the past and never in the future.

So the term "a true prediction" can only have the meaning of "a prediction that is truly a prediction" and not "a prediction that will become true" - the latter being a statement the truth of which cannot be verified until after the fact.
because a thing is eloquently expressed it should not be taken to be as necessarily true
St. Augustine, Confessions V, 6

petm

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Re: Slater's thread
« Reply #119 on: August 06, 2019, 06:22:34 AM »
Assuming of course that the future cannot be observed...

binntho

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Re: Slater's thread
« Reply #120 on: August 06, 2019, 06:26:51 AM »
Assuming of course that the future cannot be observed...
If it could it wouldn't be ...
because a thing is eloquently expressed it should not be taken to be as necessarily true
St. Augustine, Confessions V, 6

petm

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Re: Slater's thread
« Reply #121 on: August 09, 2019, 01:04:32 AM »
The Slater model website finally updated after a few weeks of nothing. At least the map did but not the graph. It's predicting 4.6 Mkm2 for Sept 27. So I still guess the Sept average will be ~4.3. If the model accuracy is consistent with previous years, then we can expect the measured Sept average to be not much lower than ~3.8, if this is an exceptionally high melt/compaction year.

Richard Rathbone

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Re: Slater's thread
« Reply #122 on: August 11, 2019, 06:48:10 PM »
Up to 4.93 for the 30th, and the dark blue continues to get higher than the light blue (i.e. the model thinks the ice has more chance of surviving/regrowing than a crude look at current conditions suggests).


petm

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Re: Slater's thread
« Reply #123 on: August 12, 2019, 05:33:52 PM »
Forecast date (+50 d) is now Oct. 1, at just over 5 Mkm2. Maybe the Sept. average is closer to 4.5? Hard to say due to the gap in reporting.

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Re: Slater's thread
« Reply #124 on: August 18, 2019, 02:04:00 PM »
Forecast date (+50 d) is now Oct. 1, at just over 5 Mkm2. Maybe the Sept. average is closer to 4.5? Hard to say due to the gap in reporting.

If I had to guess, I'd say that the forecasts made by the model stabilised towards the end of July to scenarios in which the minima was expected to be at a "normal" time (mid-September). Prior to that, either the model was (during the runs made during early July) forecasting an earlier minima (start of September), or a lower one at a later date.

It's possible, of course, that the model has been fundamentally unchanged for the entire duration, and it was forecasting an early minima and a later "stall". Difficult to know without knowing details of the modelling  ;)

Based on the assumption that the model did change, then, yes, a minima of around 4.25-4.5 Mkm2 seems the most likely "prediction". (To my eye, it looks like the missing days of output would probably have shown a gradual increase.)
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Re: Slater's thread
« Reply #125 on: August 18, 2019, 02:38:29 PM »
The slater’s forecast is very influenced by the concentration state and tendency 50 days before. The forecast between September 5 and 15 is very influenced by the relative coldness that the stormy weather caused from July 15 to 25.
I would expect, having seen the weather after July 25, the stored heat, and the current forecast, that the actual extent will follow a flatter line below or around 4 million until september 20 the least.
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petm

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Re: Slater's thread
« Reply #126 on: September 09, 2019, 06:06:05 AM »
Turns out that Slater overestimated extent loss this year relative to observation. Odd rapid breaking pattern in the end-of-season metrics, very likely not illustrative of the heat accumulated in the system. Not quite sure what to make of it.

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Re: Slater's thread
« Reply #127 on: September 19, 2019, 09:44:28 PM »
Current graph shows that the minimum of the 50-day forecasts wasn't massively far out in terms of minimum extent (it might get a smidgen closer), but I'll caveat that with a repetition of what I've said before: you can't read too much into the shape of the graph formed by the 50-day forecasts.

For all we know, the model runs that forecast a sub-4 million km2 at the start of September (and now look like it was forecasting an early minima) might have done so because the model was expecting the minima to be much lower and occur in mid-September.

Model runs performed a couple of weeks later may have revised that mid-September minima to a higher extent (very close to what actually occurred): the model forecast made for 3 or 4 days ago was pretty much bang on.
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Re: Slater's thread
« Reply #128 on: September 20, 2019, 03:18:08 AM »
For all we know, the model runs that forecast a sub-4 million km2 at the start of September (and now look like it was forecasting an early minima) might have done so because the model was expecting the minima to be much lower and occur in mid-September.

Model runs performed a couple of weeks later may have revised that mid-September minima to a higher extent (very close to what actually occurred): the model forecast made for 3 or 4 days ago was pretty much bang on.
That is my understanding of what happened.