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Napoleon
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Message 52283 - Posted: 21 Jul 2015, 14:42:36 UTC

Arctic ice melt is ahead of model predictions, I believe, at least those used by the IPCC.

Peter Wadhams, death spiral etc.

So does the BOINC model account for this ?
If not, is there any point running it ?

Profile Iain Inglis
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Message 52284 - Posted: 21 Jul 2015, 15:41:45 UTC

Some CPDN models forecast the future, or rather "a future", but many models also attempt to understand what caused the past as it is known to have happened: in those "hindcasts" the ice extent would presumably be taken from observations - in which case it doesn't matter that the extents were worse at that time than was forecast at some earlier time.

For forecasts, underestimating the ice loss would be expected to produce a "not quite as bad" world. If the people in that world were to address even that not-quite-as-bad world then they would be better prepared for the worse world that is almost inevitable given our catastrophic indolence.

Profile Byron Leigh Hatch @ team Carl Sagan
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Message 52285 - Posted: 21 Jul 2015, 17:52:38 UTC

Napoleon
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Message 52286 - Posted: 21 Jul 2015, 18:23:07 UTC - in response to Message 52284.

Some CPDN models forecast the future, or rather "a future", but many models also attempt to understand what caused the past as it is known to have happened: in those "hindcasts" the ice extent would presumably be taken from observations - in which case it doesn't matter that the extents were worse at that time than was forecast at some earlier time.

For forecasts, underestimating the ice loss would be expected to produce a "not quite as bad" world. If the people in that world were to address even that not-quite-as-bad world then they would be better prepared for the worse world that is almost inevitable given our catastrophic indolence.


Well that's a good point about being prepared , and the root of my question, because my town was flooded during the recent storm surge - and the authorities, basing their defenses on IPCC projections, weren't prepared.

So does the CPDN take into account the latest ice cap data to verify it's models ?

I know there is a bit of a fight over this because Wadhams goes with a non linear ice retreat based on observation - leading to imminent ice cap loss, whereas most modellers draw a straight line through the data and think it's less urgent.

Wouldn't it be a good test of the backcasting to compare model results with the latest ice loss data ?

Napoleon
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Message 52287 - Posted: 21 Jul 2015, 18:25:42 UTC - in response to Message 52285.

Here is some interesting information from 2013 -- the Guardian --

http://www.theguardian.com/environment/earth-insight/2013/dec/09/us-navy-arctic-sea-ice-2016-melt

The project, based out of the US Naval Postgraduate School's Department of Oceanography, uses complex modelling techniques that make its projections more accurate than others.

sorry for the Long copy and paste.



I'm familiar with that - the US navy has a more accurate model. Is it more accurate or does it agree with the CPDN modelling ?

Les Bayliss
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Message 52290 - Posted: 22 Jul 2015, 3:46:38 UTC

This needs to be taken in context.

The models used have been written over many years, by many people, at the UK Met Office, for running on several generations of supercomputers.

These people, and those providing the data sets that we run, (and getting the results that we return), are professionals, and are always looking at and for research results in the climate field.
So they'll be well aware of what your post refers to. And a lot more that doesn't make it into the popular press.

As for what data is included in different runs of our modelling, that's up to the researchers running each experiment. And if you watch the files being down loaded onto your computer, you can see some of the data ideas (for want of a better word), that are going to be used.

And the models are getting more sophisticated, as computers available to the public get more powerful.
e.g. You'll notice from the Server Status page that some use the MOSES II land scheme, and some also use TRIFFID.
The earlier models used MOSES, the original scheme. These II versions are using the latest, more detailed descriptions.
(MOSES and TRIFFID are descriptor files for various land use. e.g. vegetation, large bodies of water, high snow forming mountains, etc.)

If you look at this old one of mine under Perturbed Parameters, you can see that it took into account Sea ice, and also the file in which that was contained.
Others over the years have labels to do with ice fall.

As for what ANY military group is using, I'd prefer not to comment. I don't want people with fedoras, dark glasses, and turned up collars coming around and asking me what I'm up to.


Profile Byron Leigh Hatch @ team Carl Sagan
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Message 52291 - Posted: 22 Jul 2015, 3:52:24 UTC - in response to Message 52290.
Last modified: 22 Jul 2015, 4:02:01 UTC

Hi Les, Iain, Napoleon ... thank you for this information, excellent posts.

noderaser
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Message 52315 - Posted: 23 Jul 2015, 17:25:37 UTC - in response to Message 52290.

I don't want people with fedoras, dark glasses, and turned up collars coming around and asking me what I'm up to.


I don't the the Fedoras are standard issue anymore, unless you live in a Noir film.
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Professor Desty Nova
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Message 52326 - Posted: 24 Jul 2015, 17:04:58 UTC
Last modified: 24 Jul 2015, 17:05:44 UTC

Napoleon
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Message 52340 - Posted: 27 Jul 2015, 5:37:34 UTC - in response to Message 52291.

Hi Les, Iain, Napoleon ... thank you for this information, excellent posts.


Aye

Napoleon
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Message 52341 - Posted: 27 Jul 2015, 5:44:36 UTC - in response to Message 52290.
Last modified: 27 Jul 2015, 5:45:26 UTC

Napoleon
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Message 52342 - Posted: 27 Jul 2015, 5:56:04 UTC
Last modified: 27 Jul 2015, 5:58:22 UTC

Here's a wee bit more about this, from the latest by James Hansen

http://www.huffingtonpost.com/dr-james-hansen/multi-meter-sea-level-rise-is-an-issue-for-todays-public_b_7875828.html

...which to me says that ice modelling is something tricky that hasn't been mastered yet

Says,

In contrast, we show in a prior paper and our new paper that ice sheet models are far too sluggish compared with the magnitude and speed of sea level changes in the paleoclimate record. This is not surprising, given the primitive state of ice sheet modeling.


So would the CPDN simulations concur with this - do their ice results match with the paleoclimate record ?

Les Bayliss
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Message 52344 - Posted: 27 Jul 2015, 7:49:56 UTC

The IPCC reports are conservative because the representatives of a lot of the governments insist on "watering it down". Otherwise they can end up in strife from big business.

The originator of the University of Oxford's interest in climate, Prof Myles R. Allen (People) does, apparently, have input to IPCC reports.

A lot of the problem with ice simulation is due to the small number of polar monitoring stations, and thus the small amount of data available from there, compared to the rest of the world. Thus computer simulations of polar ice is nowhere near as good or as accurate as for the more populated parts of the planet.

Give it another 10 years, and then re-visit the subject. :)


Napoleon
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Message 52354 - Posted: 28 Jul 2015, 7:45:25 UTC - in response to Message 52344.



Give it another 10 years, and then re-visit the subject. :)




I think that'll be a visit to an expanse of open water by then.

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