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crandles

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Ice free predictions and their uncertainty
« on: August 28, 2016, 12:47:24 AM »
https://www.carbonbrief.org/guest-post-predictable-first-ice-free-arctic-summer
Quote
How predictable is the first ice-free Arctic summer?

In conclusion, our findings suggest that we cannot predict the timing of an ice-free Arctic summer with an uncertainty of less than about 25 years.

Hmm, possibly I suppose, but: If the central estimate is 10 years or less away then I wouldn't think that 25 years uncertainty would be needed. If the central estimate is over 50 years away then an uncertainty of more than 25 years might be needed?

Juan C. García

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Re: Ice free predictions and their uncertainty
« Reply #1 on: August 28, 2016, 04:43:29 AM »
Have someone ever read "How to Lie with Statistics"? I read it long time ago, like 20+ years.

When I see this kind of articles, I said that the shortest answer is my signature.  ;)
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.

Tigertown

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Re: Ice free predictions and their uncertainty
« Reply #2 on: August 28, 2016, 04:50:11 AM »
75% of all statistics are made up on the spot.

25 years is too generous of an uncertainty. That much I know.
« Last Edit: August 28, 2016, 05:05:48 AM by Tigertown »

longwalks1

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Re: Ice free predictions and their uncertainty
« Reply #3 on: August 28, 2016, 05:19:01 AM »
It appears to be based on the paper  doi:10.1002/2016GL070067

How predictable is the timing of a summer ice-free
Arctic?

Alexandra Jahn1, Jennifer E. Kay2, Marika M. Holland3, David M. Hall4

From conclusions,
Quote
Our results from the 40-member CESM LE and the 15-member CESM ME show that
due to internal variability alone, we can not predict the timing of a summer ice-free Arctic
with an uncertainty of less than 21 years. The much smaller ensembles (5–10 members)
from the CMIP5 archive show uncertainty ranges of 7–15 years due to internal variability,
which are consistent with the expectation for smaller ensembles from the bootstrapped
CESM LE. Past, present, and near future sea ice volume, trends, area, extent, and thickness
as well as global temperature metrics do not allow us to narrow the prediction
uncertainty due to internal variability within individual models.

I am puzzled about in the original source where they start talking about 5 and 10 year consecutive 1 x 10E6 ice extents. If I read it right, they are not using consecutive years, but they give the usage of consecutive years more ink than I believe it deserves. For a rugby or Canada-US football analogy it smacks of "moving the goal posts."   

Quote
Table 1. Range of years from CESM and CMIP5 ensembles when an ice free September in
the Arctic is first reached, based on different definitions of“ice-free” used in the literature. The
ensemble spread is given in parentheses after the year range and the ensemble size is given in
square parentheses after the model name
       

is found at the very end of the article with 5 and 10 year consecutive columns included.

One basis of the paper is doi:10.1175/BAMS-D-13-00255.1.

http://journals.ametsoc.org/doi/full/10.1175/BAMS-D-13-00255.1

The Community Earth System Model (CESM) Large Ensemble Project: A Community Resource for Studying Climate Change in the Presence of Internal Climate Variability

More also about posted here at
https://forum.arctic-sea-ice.net/index.php/topic,1356.msg60085.html#msg60085

In at least two places in the CESM  paper talks about a hiatus in global warming in the modelling.   

Quote
Off-shoot  experiments  have  already  started including  experiments  to  test  the  competing  hypotheses  for  hiatus  periods,  to  evaluate hurricanes in CESM1(CAM5) using high resolution time slice experiments, to force regional downscaling  simulations,  and  to  run  a  complementary  ensemble  under  RCP4.5  forcing  to assess  avoided  impacts.

This gives me pause, as I am not sure that there has been a hiatus in the Arctic.  I am not disputing that this form of modelling has value and use. I might be comparing apples and oranges. I wonder, however if CESM's value is larger outside of the Arctic. 

Quote
After initial condition memory is lost, which occurs within weeks in the atmosphere, each ensemble member evolves chaotically, affected by atmospheric circulation fluctuations characteristic of a random, stochastic process

Would using CESM have less use in an ocean environment with multi-year ice. 

A few years in the future however might convince me that I used too much ink on these studies. 


Juan C. García

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Re: Ice free predictions and their uncertainty
« Reply #4 on: August 28, 2016, 05:35:01 AM »
It upsets me that the IPCC started to use the definition of 5 consecutive years. See the poll:
https://forum.arctic-sea-ice.net/index.php/topic,1559.0.html
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.

epiphyte

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Re: Ice free predictions and their uncertainty
« Reply #5 on: August 28, 2016, 07:31:58 AM »
It upsets me that the IPCC started to use the definition of 5 consecutive years. See the poll:
https://forum.arctic-sea-ice.net/index.php/topic,1559.0.html

Quite seriously, I think that the most appropriate metric in this situation might be termed the "Gin and Tonic Test"...

I.E. When there's not enough ice to prevent it from tasting awful, there might as well not be any at all.

mmghosh

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Re: Ice free predictions and their uncertainty
« Reply #6 on: August 28, 2016, 12:30:49 PM »
From the IJIS poll thread
1980's Avg:   7.23
1990's Avg:   6.55
2000's Avg:   5.48
2003:   5.93
2004:   5.68
2005:   5.18
2006:   5.63
2007:   4.07
2008:   4.50
2009:   5.05
2010:   4.62
2011:   4.27
2012:   3.18
2013:   4.81
2014:   4.88
2015:   4.26

A straightforward linear extrapolation leads to the 2050s decade.  Isn't that bad enough?

Juan C. García

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Re: Ice free predictions and their uncertainty
« Reply #7 on: August 28, 2016, 12:51:26 PM »
From the IJIS poll thread
...
A straightforward linear extrapolation leads to the 2050s decade.  Isn't that bad enough?

It is not a linear trend. It has acceleration. And Extent is a good (and the fastest) measure to follow the status of the Arctic sea ice on a daily basis, but it should not be used to make any forecast (IMHO, NSIDC and IPCC are wrong using extent to make a forecast).

To make a forecast, you have to recognize that the Arctic sea ice is also loosing thickness. When you try to make any forecast with volume, recognizing that the melt has accelerated, then you can use a linear trend, but with less years.

Edit: Using extent and/or using the definition of "5 consecutive years" on a forecast, are ways to lie with statistics.

I like Wipneus forecasts:
« Last Edit: August 28, 2016, 02:27:12 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.

crandles

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Re: Ice free predictions and their uncertainty
« Reply #8 on: August 28, 2016, 04:10:30 PM »

It is not a linear trend. It has acceleration. And Extent is a good (and the fastest) measure to follow the status of the Arctic sea ice on a daily basis, but it should not be used to make any forecast (IMHO, NSIDC and IPCC are wrong using extent to make a forecast).

To make a forecast, you have to recognize that the Arctic sea ice is also loosing thickness.

What makes you so sure it isn't a case of 'It had acceleration' when thick MYI was being reduced significantlyand was largely no re-growing in winter, but now we are down to most being less than 2m thick, what is lost is largely regrown in the winter so it is decelerating as the models suggest will happen?

Tigertown

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Re: Ice free predictions and their uncertainty
« Reply #9 on: August 28, 2016, 04:52:05 PM »
Too many feedback systems have kicked in at this point. For just one example, albedo on land, which is being lost earlier in the melt season. The last three years, the global temperatures have set records and made a huge jump from pre-industrial averages. Arctic amplification is making it worse for the Arctic.

Richard Rathbone

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Re: Ice free predictions and their uncertainty
« Reply #10 on: August 28, 2016, 05:03:04 PM »
The first ice free September will be predictable about 2 months before it happens.

I'm rather less sure about the first ice-free June. That might well require tipping to an equable climate state, and I don't think anyone has a handle on what precipitates that.

crandles

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Re: Ice free predictions and their uncertainty
« Reply #11 on: August 28, 2016, 08:22:23 PM »
Too many feedback systems have kicked in at this point. For just one example, albedo on land, which is being lost earlier in the melt season. The last three years, the global temperatures have set records and made a huge jump from pre-industrial averages. Arctic amplification is making it worse for the Arctic.

Hmm, you choose 'the last three years' period and with all these feedback systems kicking in as you put it, 2013, 14 and 15 were higher than each of 2010, 11 and 12. Certainly can be noise but does this make you pause to wonder if perhaps all these feedback systems that are kicking in may not be very strong?

Archimid

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Re: Ice free predictions and their uncertainty
« Reply #12 on: August 28, 2016, 10:58:05 PM »
It upsets me that the IPCC started to use the definition of 5 consecutive years.

 That definition is perfectly designed to not lie about the risks while minimizing them. Within that statement is the veiled assumption that after the ice is gone for the first time it will come back. That is a huge assumption.

My layman opinion is that after the first ice free September, the freezing season will be delayed. Ice grows from the center out. If there is no ice in the North Pole then it will take sometime before the periphery gets cold enough to freeze the saltier arctic. Once the Pole is covered in ice, sea ice extent will grow rapidly (as the waves allow) and probably cover the whole arctic. But it will be very thin, not even first year ice. That ice will melt very quickly the following summer. Then the cycle begins again only with the arctic being ice free for the whole summer instead of just a few months, further delaying the freezing season. Rinse and repeat until is gone.




I am an energy reservoir seemingly intent on lowering entropy for self preservation.

Iceismylife

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Re: Ice free predictions and their uncertainty
« Reply #13 on: August 29, 2016, 12:05:05 AM »
It upsets me that the IPCC started to use the definition of 5 consecutive years.

 That definition is perfectly designed to not lie about the risks while minimizing them. Within that statement is the veiled assumption that after the ice is gone for the first time it will come back. That is a huge assumption.

My layman opinion is that after the first ice free September, the freezing season will be delayed. Ice grows from the center out. If there is no ice in the North Pole then it will take sometime before the periphery gets cold enough to freeze the saltier arctic. Once the Pole is covered in ice, sea ice extent will grow rapidly (as the waves allow) and probably cover the whole arctic. But it will be very thin, not even first year ice. That ice will melt very quickly the following summer. Then the cycle begins again only with the arctic being ice free for the whole summer instead of just a few months, further delaying the freezing season. Rinse and repeat until is gone.
Ice forms everywhere that the surface water local air temp. gets cold enough.

Tigertown

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Re: Ice free predictions and their uncertainty
« Reply #14 on: August 29, 2016, 12:10:34 AM »
Too many feedback systems have kicked in at this point. For just one example, albedo on land, which is being lost earlier in the melt season. The last three years, the global temperatures have set records and made a huge jump from pre-industrial averages. Arctic amplification is making it worse for the Arctic.

Hmm, you choose 'the last three years' period and with all these feedback systems kicking in as you put it, 2013, 14 and 15 were higher than each of 2010, 11 and 12. Certainly can be noise but does this make you pause to wonder if perhaps all these feedback systems that are kicking in may not be very strong?
Naw, I live in the real world, not happy land.

Archimid

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Re: Ice free predictions and their uncertainty
« Reply #15 on: August 29, 2016, 02:22:34 AM »
Ice forms everywhere that the surface water local air temp. gets cold enough.

Yes of course. However take a look at the first few months of the melting seasons. Ice do not grow in random patches throughout the arctic. It grows from the ice mass out, from the arctic islands out and from the arctic periphery in.

Temperature is not the only factor in the formation of arctic sea ice. Salinity and waves also play  an important part. When there sea ice present then the water adjacent to the ice has a more favorable environment to form ice. The ice calms waves and creates its own micro-weather. When there is no sea ice present then things like waves and mixing prevent ice from forming.

In the case of sea ice less arctic then waves and salinity will prevent formation until ice is formed in around the arctic islands and it grows from the peripheral coasts in. Thus rapid ice formation will be delayed for months, after the first blue ocean event.
I am an energy reservoir seemingly intent on lowering entropy for self preservation.

Michael Hauber

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Re: Ice free predictions and their uncertainty
« Reply #16 on: August 29, 2016, 05:36:30 AM »
Too many feedback systems have kicked in at this point. For just one example, albedo on land, which is being lost earlier in the melt season.

The feedbacks currently operating are mostly the same as have been operating for thousands of years.  In most cases they do not kick in and out, but amplify every change in climate to some extent.  Nearly all The same feedbacks were operating in the little ice age as the medieval warm period as will be operating in another hundred years of AGW.

As an example the land albedo feedback was certainly operating throughout the medieval warm period (less land snow), the little ice age (more snow) and is still operating, but is weaker than it has been at any stage in recorded history.  Modelling shows that the warmer the planet is, the less change in albedo for ice loss for every degree of warming.  Other feedbacks show different behaviours - for instance water vapour feedback gets gradually stronger as the world warms.
Climate change:  Prepare for the worst, hope for the best, expect the middle.

Tigertown

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Re: Ice free predictions and their uncertainty
« Reply #17 on: August 29, 2016, 06:14:52 AM »
Argue with my big friend. His name is NOAA.

www.noaa.gov/arctic-set-for-record-breaking-melt
« Last Edit: August 29, 2016, 02:43:10 PM by Tigertown »

Juan C. García

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Re: Ice free predictions and their uncertainty
« Reply #18 on: August 29, 2016, 06:33:59 PM »

It is not a linear trend. It has acceleration. And Extent is a good (and the fastest) measure to follow the status of the Arctic sea ice on a daily basis, but it should not be used to make any forecast (IMHO, NSIDC and IPCC are wrong using extent to make a forecast).

To make a forecast, you have to recognize that the Arctic sea ice is also loosing thickness.

What makes you so sure it isn't a case of 'It had acceleration' when thick MYI was being reduced significantlyand was largely no re-growing in winter, but now we are down to most being less than 2m thick, what is lost is largely regrown in the winter so it is decelerating as the models suggest will happen?

Hi Crandles.

I can beleive that there could be a deceleration, but definitely I see the first year of an ice-free Arctic before 2035 (and I believe that I am being conservative with this forecast).

I could be wrong but in my opinion, the IPCC models could be intentionally wrong. We have been seeing different versions of this graph, long time ago. This one comes from the US National Climate Assessment 2014. What the graph means is that reality is worst worse than the Model simulations. In this graph, clearly says that "Extrapolation of the present observed trend suggests an essentially ice-free Arctic in summer before mid-century".

Suddenly, the IPCC changes the definition of ice-free Arctic and starts talking about 5 consecutive years. And then the models are alright. Isn´t this a way to try to avoid the subject of when we are going to have an ice-free Arctic? Can we accept the argument of "Several models agree that..." knowing that the models haven't described the reality? Or accept that because 2016 did not beat the 2012 record low, then everything seems to be delayed? Isn't 2016 bad enough? Can we forget that all this is based on extent trends, not taking into account the volume?

In my (not humble) opinion, what this article is trying to do is just misinform the general public. Climate change is real but no so bad. We are not sure when we will have an ice-free Arctic. Maybe 2100.
« Last Edit: August 29, 2016, 07:32:04 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.

Neven

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Re: Ice free predictions and their uncertainty
« Reply #19 on: August 29, 2016, 07:34:08 PM »
Naw, I live in the real world, not happy land.

Argue with my big friend. His name is NOAA.

Could you try and leave the 'smart ass' home when making comments, please? Thanks.
Il faut comparer, comparer, comparer, et cultiver notre jardin

crandles

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Re: Ice free predictions and their uncertainty
« Reply #20 on: August 29, 2016, 08:37:20 PM »
All models are wrong and it is quite possible for all models to be too slow in reducing the ice below 1m km2 without needing to invoke intentionally wrong models. Suggesting that seems disrespectful to hard working scientists. I think conspiracy theories are generally unlikely and particularly so amongst argumentative scientists - too much reputation to gain by blowing the whistle.

Yes, the models were too slow in removing thick MYI. How much relevance does this have to rate of removal of ice which re-grows to similar thickness each winter? Maybe the models will be too slow again, but I don't think we can be sure of this and it could go either way. 3 or 4 years since 2012 isn't enough to tell. 2013-15 were surprising given the data to 2012 and that doesn't seem to encourage belief that models will be too slow again but there isn't enough data.

Juan C. García

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Re: Ice free predictions and their uncertainty
« Reply #21 on: August 29, 2016, 09:39:42 PM »
All models are wrong and it is quite possible for all models to be too slow in reducing the ice below 1m km2 without needing to invoke intentionally wrong models. Suggesting that seems disrespectful to hard working scientists. I think conspiracy theories are generally unlikely and particularly so amongst argumentative scientists - too much reputation to gain by blowing the whistle.

Yes, the models were too slow in removing thick MYI. How much relevance does this have to rate of removal of ice which re-grows to similar thickness each winter? Maybe the models will be too slow again, but I don't think we can be sure of this and it could go either way. 3 or 4 years since 2012 isn't enough to tell. 2013-15 were surprising given the data to 2012 and that doesn't seem to encourage belief that models will be too slow again but there isn't enough data.

I am not trying to disqualify all models and certainly, I want to respect the honest scientists working on these projects. But IPCC comes from "Intergovernmental Panel on Climate Change" and they are more than 10,000 people. How many of them are real and honest scientists? So, from my point of view, some thousand(s) IPCC people are politicians and it could be another thousand coming from the fossil fuel industry.

If we have Exxon, Hunt and others paying to misinform the general public, can we be so naive to think that everything that it is happening inside the IPCC is well intentioned? Just a question, even that I am sure that there are also scientists doing their honest work. At this point, I also want to recognize that I use information coming from the IPCC and I find it reliable. But I am concerned that global warming is happening much faster than what the IPCC is recognizing.
« Last Edit: August 29, 2016, 10:14:59 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.

Tigertown

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Re: Ice free predictions and their uncertainty
« Reply #22 on: August 29, 2016, 10:07:23 PM »
Naw, I live in the real world, not happy land.

Argue with my big friend. His name is NOAA.

Could you try and leave the 'smart ass' home when making comments, please? Thanks.
Sorry,Neven. You know I am usually the last to do that. I just got the feeling these guys were trying to pick a row, and that they were saying things they did not believe themselves only for that effect. I can't believe anyone on this forum would really feel that way. I guess I could be wrong.
Oh, and I was actually sincere, because where I live the world has changed so much, and I have neighbors and friends suffering because of it. However, will say no more.

budmantis

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Re: Ice free predictions and their uncertainty
« Reply #23 on: August 30, 2016, 07:19:52 AM »
I can commiserate Tigertown. There have been times I've felt the same way. By the way, thanks for the tip about adding smileys. Don't know why, I just cant get it to work! When I click on the smiley, the cursor disappears.

Regards,

Bud

Tigertown

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Re: Ice free predictions and their uncertainty
« Reply #24 on: August 30, 2016, 08:04:37 AM »
Juan C. Garcia,
" But I am concerned that global warming is happening much faster than what the IPCC is recognizing."
   Rightly so. Scientist recently discovered that many fats they thought were bad for you to consume  ( the ones in eggs, for example) are actually good for you. As a matter of fact, you can't properly absorb vitamins that your body needs without certain fats. Also, they discovered that some fats kill viruses and bacteria and fungi that cause other health problems.As a matter of fact, the right ones(mct's) kill the very bacteria that causes heart diseases previously blamed on fats. The problem is, however, they can't get other scientist or doctors to change what they always have believed and taught, because they had believed it  for so long. I think a similar thing is happening here with this issue. They believed for so long that they had the rate of warming figured out, that they can't adjust what they believe, though it is happening before their eyes.
« Last Edit: August 30, 2016, 08:23:00 AM by Tigertown »

abbottisgone

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Re: Ice free predictions and their uncertainty
« Reply #25 on: August 30, 2016, 08:52:15 AM »

It is not a linear trend. It has acceleration. And Extent is a good (and the fastest) measure to follow the status of the Arctic sea ice on a daily basis, but it should not be used to make any forecast (IMHO, NSIDC and IPCC are wrong using extent to make a forecast).

To make a forecast, you have to recognize that the Arctic sea ice is also loosing thickness.

What makes you so sure it isn't a case of 'It had acceleration' when thick MYI was being reduced significantlyand was largely no re-growing in winter, but now we are down to most being less than 2m thick, what is lost is largely regrown in the winter so it is decelerating as the models suggest will happen?
.. This is why my favourite graphs are of the MYI  ;)

IMHO they are the sole reason for why the internet exists !
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mmghosh

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Re: Ice free predictions and their uncertainty
« Reply #26 on: August 30, 2016, 10:13:03 AM »
The thing is,  IJIS is a measurement,  however indirect.  PIOMAS is a model.

People will generally trust direct or indirect measurements more than models.

Michael Hauber

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Re: Ice free predictions and their uncertainty
« Reply #27 on: August 30, 2016, 10:56:49 AM »
Argue with my big friend. His name is NOAA.

www.noaa.gov/arctic-set-for-record-breaking-melt

The opinions of a marine biologist, and a media officer.  But they work at NOAA so they must be experts on Arctic ice.  Is the article somehow relevant to the topic at hand?
Climate change:  Prepare for the worst, hope for the best, expect the middle.

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Re: Ice free predictions and their uncertainty
« Reply #28 on: August 30, 2016, 12:06:23 PM »
Too many feedback systems have kicked in at this point. For just one example, albedo on land, which is being lost earlier in the melt season.

The feedbacks currently operating are mostly the same as have been operating for thousands of years.  In most cases they do not kick in and out, but amplify every change in climate to some extent.  Nearly all The same feedbacks were operating in the little ice age as the medieval warm period as will be operating in another hundred years of AGW.

As an example the land albedo feedback was certainly operating throughout the medieval warm period (less land snow), the little ice age (more snow) and is still operating, but is weaker than it has been at any stage in recorded history.  Modelling shows that the warmer the planet is, the less change in albedo for ice loss for every degree of warming.  Other feedbacks show different behaviours - for instance water vapour feedback gets gradually stronger as the world warms.
Simply wrong!

<snip>

<Slow down, aig. Don't start all over again; N.>
« Last Edit: August 30, 2016, 12:50:31 PM by Neven »
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Re: Ice free predictions and their uncertainty
« Reply #29 on: August 30, 2016, 01:08:53 PM »

I am not trying to disqualify all models and certainly, I want to respect the honest scientists working on these projects. But IPCC comes from "Intergovernmental Panel on Climate Change" and they are more than 10,000 people. How many of them are real and honest scientists? So, from my point of view, some thousand(s) IPCC people are politicians and it could be another thousand coming from the fossil fuel industry.

Please have a look at the IPCC website about their organization. IPCC is a very small group, but for there reports they invite scientist from all over the world.

From IPCC AR5, WGI, chapter 11.3.4.1 Sea Ice (page 995, published in 2013)
Quote
Though most of the CMIP5 models project a nearly ice-free Arctic (sea ice extent less than 1 × 106 km2 for at least 5 consecutive years) at the end of summer by 2100 in the RCP8.5 scenario (see Section 12.4.6.1), some show large changes in the near term as well. Some previous models project an ice-free summer period in the Arctic Ocean by 2040 (Holland et al., 2006), and even as early as the late 2030s using a criterion of 80% sea ice area loss (e.g., Zhang, 2010). By scaling six CMIP3 models to recent observed September sea ice changes, a nearly ice-free Arctic in September is projected to occur by 2037, reaching the  rst quartile of the distribution for timing of September sea ice loss by 2028 (Wang and Overland, 2009).
The full chapter 11 was written by around 55 authors. (I assume not all were involved in the sea ice paragraph.) However the authors did not base their wording only on own publications but analysed a broad spectrum of the scientific literature. Before publication the report was reviewed by many others.

It is the final Synthesis Report and the "Summary for policymakers"  were the big (political) discussions about the wording starts. Not about text on page 995.

PS: haven a look at the report: there is also something about "ice free in 2016" (http://www.ipcc.ch/pdf/assessment-report/ar5/wg1/WG1AR5_Chapter11_FINAL.pdf)

crandles

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Re: Ice free predictions and their uncertainty
« Reply #30 on: August 30, 2016, 01:29:45 PM »

PS: haven a look at the report: there is also something about "ice free in 2016" (http://www.ipcc.ch/pdf/assessment-report/ar5/wg1/WG1AR5_Chapter11_FINAL.pdf)

seems worth quoting the section:

Quote
11.3.4.1 Sea Ice
Though most of the CMIP5 models project a nearly ice-free Arctic (sea
ice extent less than 1 × 106
 km2
 for at least 5 consecutive years) at the
end of summer by 2100 in the RCP8.5 scenario (see Section 12.4.6.1),
some show large changes in the near term as well. Some previous
models project an ice-free summer period in the Arctic Ocean by 2040
(Holland et al., 2006), and even as early as the late 2030s using a
criterion of 80% sea ice area loss (e.g., Zhang, 2010). By scaling six
CMIP3 models to recent observed September sea ice changes, a nearly
ice-free Arctic in September is projected to occur by 2037, reaching the
first quartile of the distribution for timing of September sea ice loss by
2028 (Wang and Overland, 2009). However, a number of models that
have fairly thick Arctic sea ice produce a slower near-term decrease in
sea ice extent compared to observations (Stroeve et al., 2007). Based
on a linear extrapolation into the future of the recent sea ice volume
trend from a hindcast simulation conducted with a regional model of
the Arctic sea ice–ocean system (Maslowski et al., 2012) projected that
it would take only until about 2016 to reach a nearly ice-free Arctic
Ocean in summer. However, such an approach not only neglects the
effect of year-to-year or longer-term variability (Overland and Wang,
2013) but also ignores the negative feedbacks that can occur when
the sea ice cover becomes thin (Notz, 2009). Mahlstein and Knutti
(2012) estimated the annual mean global surface warming threshold
for nearly ice-free Arctic conditions in September to be ~2°C above the
present derived from both CMIP3 models and observations.

So what I was saying has support in the scientific literature but some people feel I am saying such things without believing it only for that effect. Do we want to be an alarmist echo chamber or a place for sensible discussions?

I am trying not to react so I will just say thank you Neven for the moderation, hope a lot more isn't needed.

Archimid

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Re: Ice free predictions and their uncertainty
« Reply #31 on: August 30, 2016, 03:09:34 PM »
11.3.4.1 Sea Ice
Though most of the CMIP5 models project a nearly ice-free Arctic (sea
ice extent less than 1 × 106 km2 for at least 5 consecutive years) at the
end of summer by 2100 in the RCP8.5 scenario (see Section 12.4.6.1),
some show large changes in the near term as well. Some previous
models project an ice-free summer period in the Arctic Ocean by 2040
(Holland et al., 2006), and even as early as the late 2030s using a
criterion of 80% sea ice area loss (e.g., Zhang, 2010). By scaling six
CMIP3 models to recent observed September sea ice changes, a nearly
ice-free Arctic in September is projected to occur by 2037, reaching the
first quartile of the distribution for timing of September sea ice loss by
2028 (Wang and Overland, 2009). However, a number of models that
have fairly thick Arctic sea ice produce a slower near-term decrease in
sea ice extent compared to observations (Stroeve et al., 2007). Based
on a linear extrapolation into the future of the recent sea ice volume
trend from a hindcast simulation conducted with a regional model of
the Arctic sea ice–ocean system (Maslowski et al., 2012) projected that
it would take only until about 2016 to reach a nearly ice-free Arctic
Ocean in summer. However, such an approach not only neglects the
effect of year-to-year or longer-term variability (Overland and Wang,
2013) but also ignores the negative feedbacks that can occur when
the sea ice cover becomes thin (Notz, 2009). Mahlstein and Knutti
(2012) estimated the annual mean global surface warming threshold
for nearly ice-free Arctic conditions in September to be ~2°C above the
present derived from both CMIP3 models and observations.


All those references are from before the 2012 summer and before the 2016 winter/summer. It is important to note that those numbers also represents downward adjustments. Before 2007 the arctic was projected to be gone by 2070. After 2007 happened they were corrected  to project ice free by mid century and after 2012 it was adjusted to project ice free before 2050 and constantly ice free by 2050.

I would imagine that after the 2016 winter, and the non recovery from 2007 and 2012, the models will be further adjusted down.

As a layman, seeing this streak of underestimations places a lot of doubt in the actual capacity of scientist to predict the outcome of the arctic. I don't think it is because they are stupid or lazy or evil. It's simply a matter of not having enough data. There is plenty of data on the 1979-2004 arctic, but the 2005-2016 melting arctic is a new thing of which scientist can only speculate.  The  constant downward adjustments to the projections and the sheer uncertainty of climate change  calls for much more caution and much less "don't worry, it will be alright".
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Tigertown

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Re: Ice free predictions and their uncertainty
« Reply #32 on: August 30, 2016, 03:11:18 PM »
Argue with my big friend. His name is NOAA.

www.noaa.gov/arctic-set-for-record-breaking-melt

The opinions of a marine biologist, and a media officer.  But they work at NOAA so they must be experts on Arctic ice.  Is the article somehow relevant to the topic at hand?
Could have been the local dog catcher or anybody else, if they know when the snow melted. You should not judge people by their livelihood by the way. That is only part of what a person is. If it melts earlier in the year, you catch more rays for the year. I used the term kicked in, which perhaps I should have said kicked in to another gear. If NOAA and NASA believe it getting warmer faster and that its amplified in the Arctic, and you don't believe them, I really don't know what else to say.

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Re: Ice free predictions and their uncertainty
« Reply #33 on: August 30, 2016, 06:41:32 PM »
Could have been the local dog catcher or anybody else, if they know when the snow melted. You should not judge people by their livelihood by the way. That is only part of what a person is. If it melts earlier in the year, you catch more rays for the year. I used the term kicked in, which perhaps I should have said kicked in to another gear. If NOAA and NASA believe it getting warmer faster and that its amplified in the Arctic, and you don't believe them, I really don't know what else to say.
Tigertown,
I think no one spoke negatively against your concepts. They were just modulating your opinion. Nothing shows that there are new feedback mechanisms in only three years of sampling, not even that old ones have accelerated. But as far as I understand no one has denied that these mechanisms exist and that the warming is amplified in the Arctic.

Juan C. García

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Re: Ice free predictions and their uncertainty
« Reply #34 on: August 30, 2016, 10:01:45 PM »
Juan C. Garcia,
" But I am concerned that global warming is happening much faster than what the IPCC is recognizing."
...
The problem is, however, they can't get other scientist or doctors to change what they always have believed and taught, because they had believed it  for so long. I think a similar thing is happening here with this issue. They believed for so long that they had the rate of warming figured out, that they can't adjust what they believe, though it is happening before their eyes.

They have to change and also we have to change our way of thinking. We can fool ourselves and of course, we can fool other people with less knowledge than us.

But we are not going to fool nature. Nature is going at its own pace. So we better don't fool others and don't fool ourselves: the consequences will be greater.
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.

Juan C. García

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Re: Ice free predictions and their uncertainty
« Reply #35 on: August 30, 2016, 10:19:27 PM »
The thing is,  IJIS is a measurement,  however indirect.  PIOMAS is a model.

People will generally trust direct or indirect measurements more than models.

It is true that extent is a measure, while PIOMAS volume is just a model. Nevertheless, volume is the real thing, area [or extent] is just part of it. Even that volume is hard to measure and instead of 77.6%, it could be 75% or 70%, volume will always show greater loss than extent and the forecast of ice-free will always be sooner.

It is the story of the blind men describing an elephant. We have no to make the effort to look to the whole picture.

« Last Edit: August 30, 2016, 10:42:19 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.

Juan C. García

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Re: Ice free predictions and their uncertainty
« Reply #36 on: August 31, 2016, 02:17:08 AM »

Please have a look at the IPCC website about their organization. IPCC is a very small group, but for there reports they invite scientist from all over the world.


I was sure I read 12,000 people that participated in the report, even though most of them participated for free. But I checked and you are right. They are less:

Quote
More than 830 Authors and Review Editors from over 80 countries were selected to form the Author teams that produced the Fifth Assessment Report (AR5).They in turn drew on the work of over 1,000 Contributing Authors and about 2,000 expert reviewers who provided over 140,000 review comments.
 See the complete list of AR5 Authors and Review Editors. For statistics and regional coverage among the author teams see the AR5 page.
 For the Fourth Assessment Report (AR4) released in 2007, over 3,500 experts coming from more than 130 countries contributed to the report (+450 Lead Authors, +800 Contributing Authors, and +2,500 expert reviewers providing over 90,000 review comments).
http://www.ipcc.ch/organization/organization_structure.shtml
It is not a question of how many people participated. I still believe that it is a mistake to change the definition of ice-free Arctic to ask for 5 consecutive years. In my opinion, it is going to be bad if we start to have several years of less than 3 million km2 on extent on the period 2017-2030. So why is the IPCC talking about 5 consecutive years with ice below one million km2? Seems that they believe that ice on Greenland or permafrost melt will not be a problem until this condition is met.
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.

Juan C. García

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Re: Ice free predictions and their uncertainty
« Reply #37 on: August 31, 2016, 02:45:34 AM »
Returning to the main question on this topic: "...we cannot predict the timing of an ice-free Arctic summer with an uncertainty of less than about 25 years" I believe that it is a lie.

2016+25=2041

Defining “ice-free” as "daily sea ice extent of less than one million square kilometres on one year", we can open a poll on this Forum and ask to see how many of us believe that they expect to have the ice-free Arctic, before and after 2041.

From my point of view, I believe that Wipneus forecast (based on volume) could be closer to the true, and we can talk about natural variability, but we will not have this help for 20 years.

Edit September 1st, 2016: I add "daily" to the definition of ice-free Arctic, just to avoid the use of NSIDC monthly average, because it is not formally (or statistically) an average.
« Last Edit: September 01, 2016, 07:22:41 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.

mmghosh

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Re: Ice free predictions and their uncertainty
« Reply #38 on: September 02, 2016, 03:37:25 AM »
IMO when IJIS falls below 1 million on a single day in September will be when the public, and the media be finally convinced.

A dramatic number, a black swan event that will finally bust the public perception of the envelope.  Our quibbles here will become moot, well, they're probably moot anyway, but still.

budmantis

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Re: Ice free predictions and their uncertainty
« Reply #39 on: September 02, 2016, 05:27:18 AM »
IMO when IJIS falls below 1 million on a single day in September will be when the public, and the media be finally convinced.

A dramatic number, a black swan event that will finally bust the public perception of the envelope.  Our quibbles here will become moot, well, they're probably moot anyway, but still.

Reaching 1 million should get everyone's attention, but I doubt that it will. I think that a significant percentage of denier's, probably more than half are too entrenched in their views and/or don't see an ice-free arctic as a problem. They wont change their minds until the consequences of an ice-free arctic are staring them in the face.

abbottisgone

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Re: Ice free predictions and their uncertainty
« Reply #40 on: September 02, 2016, 09:58:39 AM »
Juan,

1 milion sq km would be an abomination: to ask that that condition be repeated three five ( :o :o :o)<headshake> times <!another headshake> before begging the world to do something would in my opinion amount to global genocide!

I know people in level 8 positions concerned about todays long term weather forecast!!!!



..
But I left school and grew my hair
They didn't understand
They wanted me to be respected as
A doctor or a lawyer man
But I had other plans..........

S.Pansa

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Re: Ice free predictions and their uncertainty
« Reply #41 on: September 08, 2016, 06:45:28 PM »
This post is an answer to Peter Ellis from a discussion we and others have about the IPCC- definition of an ice-free Arctic as "when sea ice extent is less than 10 6  km 2  for at least five consecutive years". I thought this discussion is more appropriate in this thread. Neven, if I was wrong, feel free to move this.

Well maybe - but I am not convinced, even more so as you, for some odd reason, keep mentioning a conspiracy here.
Alleging that changes are silently being made to IPCC reports for political reasons, coupled with comments like "I'm wondering about the IPCC integrity process" look, sound and smell like conspiracy theory to me. Call it what you will.

1) The figure caption reads as follows:

Quote
Figure SPM.7: ... (b) Northern Hemisphere September sea ice extent (5 year running mean) ...   The dashed line represents nearly ice-free conditions (i.e., when
sea ice extent is less than 10 6  km 2  for at least five consecutive years).  ... 

So first they say "5 year running mean" and 9 lines later (in the original caption) they all of a sudden change to "five consecutive years"?

Exactly my point.  The first draft said  "5 year running mean", and that's what the graph shows.  In the final draft, the bracketed part "(i.e. when sea ice extent is.... etc)" was added, without changing the graph or any of the other associated text.  It's bracketed, and starts with 'i.e.' - both signs that it is simply an attempt to clarify the foregoing text, not to alter its meaning.

Hi Peter,

after some sleep I think you might be right. But the fact remains, that the addition "for at least five consecutive years" does alter the meaning of the foregoing text "5 year running mean" and not clarify it. Or am I wrong on this?
And as, according to P-maker, figure captions "may be changed by the secretariat in consultation with the scientists afterwards" I find it weird that a Scientist involved in the IPCC process can't distinguish between a 5 year running mean and 5 consecutive years.

Anyhow. I asked aunt Google for help and - generous as she is - she came up with some infos that might shed some more light on the matter.

- First I found this article in Planet Earth from August 2015 about an ice-free summer in the Arctic by Prof. Ed Hawkins.

- Who is Dr. Ed Hawkings? He is "Climate scientist in the National Centre for Atmospheric Science (NCAS) at the University of Reading. IPCC AR5 Contributing Author." (from here about an ice-free summer in the Arctic by Prof. Ed Hawkins.

As it turns out he has contributed to the TS of AR5, WGI. So my guess is he should know why they added "5 consecutive years" I might be wrong tough). On page 21 he writes:

Quote
The Intergovernmental Panel on Climate Change (IPCC) concluded it was likely that the Arctic would be reliably ice-free in September before 2050, assuming high future greenhouse-gas emissions (where ‘reliably ice-free’ means five consecutive years with less than a million square kilometres of sea ice). Individual years will be ice-free sometime earlier – in the 2020s, 2030s or 2040s – depending on both future greenhouse- gas emissions and the natural erratic fluctuations.

- Second: In a more recent article on Climate depot he is quoted(last paragraph):

Quote
Dr Hawkins said the Intergovernmental Panel on Climate Change, the UN’s climate science advisory body, had forecast that the Arctic would be “reliably ice-free”, meaning more than five consecutive years below one million sq km, by the mid-21st century.
Dr Hawkins said: “Putting a precise date on when we see the first days or weeks that are ‘ice-free’ is unwise because of the chaotic nature of the climate system and uncertainties in future greenhouse gas emissions.”

So the idea was, he says, to find a measure of ‘reliably ice-free’, whatever that means. And, accroding to this at least, "5 consecutive years" seems to be meant literally and not as an explanation of a 5 year running mean (Or am I reading this wrong again?)

One thing is sure: By his own admission, this definition will change the date for an ice-free Arctic from the 20s, 30s to later decades.
But are "5 consecutive years" more reliable as a 5 year running mean or a single year? And what is the scientific basis of this definition? I have no clue - I hope others do. The best thing would probably be to ask Dr Hawkins himself.
Any native speaking volunteers out there?   :)

« Last Edit: September 08, 2016, 06:55:13 PM by S.Pansa »

Peter Ellis

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Re: Ice free predictions and their uncertainty
« Reply #42 on: September 08, 2016, 09:37:48 PM »
the fact remains, that the addition "for at least five consecutive years" does alter the meaning of the foregoing text "5 year running mean" and not clarify it. Or am I wrong on this?

I have no argument with that.

And as, according to P-maker, figure captions "may be changed by the secretariat in consultation with the scientists afterwards" I find it weird that a Scientist involved in the IPCC process can't distinguish between a 5 year running mean and 5 consecutive years.

I suspect (but may be being overly generous) that this was inserted by "the secretariat" misunderstanding what the scientist was saying. Consulting scientists doesn't mean correctly interpreting the results of that consultation, unfortunately.

Not sure if your Google findings help - they both come from after the report, at which point any competent scientist will be referring back to the agreed text to define the consensus view, and then explaining based on that. He's doing basically the same thing as we are in this thread - pointing out that an individual ice-free year will be definition come earlier than five consecutive ice-free years (or indeed an ice-free 5-year running mean). 

Might be worth checking with him, I suppose - but the larger point he's making is that the first single ice-free year is both completely unpredictable and largely irrelevant in scientific (rather than psychological) terms. Trying to forecast individual years is a mug's game.

Archimid

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Re: Ice free predictions and their uncertainty
« Reply #43 on: September 08, 2016, 10:13:26 PM »
Quote
The larger point he's making is that the first single ice-free year is both completely unpredictable and largely irrelevant in scientific (rather than psychological) terms.

To me that is a an extraordinary claim.  I honestly don't know what to say about it that could not be offensive. I mean, really? The first ice free Arctic in millions of years not scientifically interesting?

C'mon.
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Peter Ellis

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Re: Ice free predictions and their uncertainty
« Reply #44 on: September 09, 2016, 09:55:55 AM »
Of course the consequences of an ice-free Arctic are interesting! The details of whether random variability means that it happens in 2020, 2025 or 2030... not so much.

skanky

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Re: Ice free predictions and their uncertainty
« Reply #45 on: September 09, 2016, 11:39:40 AM »
Ed Hawkins runs this blog, for those who may want to discuss it with him:

http://www.climate-lab-book.ac.uk/

 :)

Bill Fothergill

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Re: Ice free predictions and their uncertainty
« Reply #46 on: September 09, 2016, 11:52:50 AM »
Of course the consequences of an ice-free Arctic are interesting! The details of whether random variability means that it happens in 2020, 2025 or 2030... not so much.

Peter, I'm pretty sure I understood the point you were making all along.

However, I can also understand how easy it is to be misinterpreted, especially when, as in this instance, a phrase you employed was taken on its own - without your accompanying contextual setting.

6roucho

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Re: Ice free predictions and their uncertainty
« Reply #47 on: September 09, 2016, 12:24:20 PM »
Surely predictability hinges on the nature of the decline? Will the ice melt out in a linear fashion, or will it undergo a state change? If it's a state change, then we can't in principle predict the timing of the event by extrapolating trends, since a non-linear event is characterised by divergence from historical behaviours.
« Last Edit: September 09, 2016, 12:41:32 PM by 6roucho »

crandles

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Re: Ice free predictions and their uncertainty
« Reply #48 on: September 09, 2016, 12:37:29 PM »
Ed Hawkins runs this blog, for those who may want to discuss it with him:

http://www.climate-lab-book.ac.uk/

 :)

http://www.climate-lab-book.ac.uk/2016/predicting-an-ice-free-arctic-summer/

seems an excellent place to ask the question. (Think I should let Juan C. García or someone who has done more of the work tracking down what happened a shot at it before someone like me barges in.)

Archimid

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Re: Ice free predictions and their uncertainty
« Reply #49 on: September 09, 2016, 12:41:12 PM »
Out of context?  Not only is the right context, it is the exact reason why a 5 year ice free definition was chosen over a single year. To minimize the significance of one single year without ice. It's a brilliant strategy.

I get it you.  You assume once the arctic is gone the world's climate will not significantly change. The jet stream will remain the same. Atmospheric patterns will remain the same. The salty Atlantic water will not mix with the Arctic ocean. The changes in albedo from an ice covered ocean to a water covered ocean won't matter. Unknown unknowns be dammed.


  Honestly, diminishing the significance of the first ice free arctic in millions of years sounds like madness to me. That would be perfectly fine for some random internet troll, but when this is happening at the front line of defense against climate change, the IPCC, its really disheartening.

How many people would be digging for answers to the uncertainties of an ice free arctic if they knew it will happen within 10 years?  How many people would prepare for the real but hidden from view worst case scenarios of such event? How many people would change their lifestyle to a low carbon one if they knew the real risks they face in their lifetimes? No worries, no response, no change. We'll just sit here and wait for it to happen.

I'm very sadden to see this written here and not only go without rebuttal, but be seconded. My hope is dimming. We will have an ice free arctic, because it is an irrelevant event. I pray you are right, but everything I know about the scientific process, uncertainty, risk assessment and society tells me that you and the IPCC are tragically underestimating the significance of an ice free arctic.






I am an energy reservoir seemingly intent on lowering entropy for self preservation.