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How accurate are modern climate models?


Filski

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Posted
  • Location: Sydney, Australia
  • Location: Sydney, Australia
    The accuracy of computer models that predict climate change over the coming decades has been the subject of debate among politicians, environmentalists and even scientists. A new study by meteorologists at the University of Utah shows that current climate models are quite accurate and can be valuable tools for those seeking solutions on reversing global warming trends. Most of these models project a global warming trend that amounts to about 7 degrees Fahrenheit over the next 100 years.

    http://www.physorg.com/news126356149.html

    paper

    http://www.inscc.utah.edu/~reichler/public...7_BAMS_CMIP.pdf

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    Posted
  • Location: Brighouse, West Yorkshire
  • Location: Brighouse, West Yorkshire

    Thanks for that Filski. An interesting read.

    The paper compares older generations of climate models against newer ones and, not suprisingly, the newer, more advanced models do a better job of simulating present climate from past observations.

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    Posted
  • Location: Colchester, Essex, UK (33m ASL)
  • Location: Colchester, Essex, UK (33m ASL)

    The way I read the paper is that no true conclusion can be drawn apart from the fact they the models are more realistic now but how realistic is inconclusive as too many variables and unknowns involved.

    If accuracy or realisism is 100/100, older models had 10/100, the latest say 50/100, that is a great improvement, but still a long way from 100/100.

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    Posted
  • Location: Sydney, Australia
  • Location: Sydney, Australia
    The way I read the paper is that no true conclusion can be drawn apart from the fact they the models are more realistic now but how realistic is inconclusive as too many variables and unknowns involved.

    If accuracy or realisism is 100/100, older models had 10/100, the latest say 50/100, that is a great improvement, but still a long way from 100/100.

    100/100 will never be acheived. It is not possible and should not be desired since it assumes a complete knowledge of how climate systems behave. This is impossible since no matter how fine the gridded data there will always a finer level of detail missed. It is unreasonable to request a perfect model and even states this in the paper (pg 4). Detractors of the AGW theory always state that we cannot know everything and then complain when the models are not 100% accurate. They set themselves up for disappointment.

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    Posted
  • Location: Harrogate, N Yorks
  • Location: Harrogate, N Yorks

    In answer to the original question - not even remotely accurate. They couldn't even predict the intensity of this year's La Nina (or before you leap on me for the short time scale the complete stop in global temperature rise so far this century, as measured by satellites), so how the heck can they be expected to calculate the temperature 10, 20, 50 years out when their margins for error are at best 20% per decade (making them no better than a guess mid century). Do anybody believe they have successfully modelled this:

    post-7195-1208787247_thumb.jpg

    with enough accuracy to base global economic decisions on?

    I don't think so....

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    Posted
  • Location: just south of Doncaster, Sth Yorks
  • Location: just south of Doncaster, Sth Yorks

    I think perhaps you are posting that with tongue in cheek, as your rather bold statement is a bit thin on factual evidence.

    Mind you it depends on what any of us term as accuracy. very long range lrf is looked upon as accurate if you get the type of airmass correct, trying to predict El Nino or La Nina onsets is even more fraught. Nevertheless the prediction of La Nina, done last year, was sufficiently accurate for both the autumn, winter and spring general weather patterns for the UK to have a fairly accurate prediction by the UK Met Office.

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    Posted
  • Location: Harrogate, N Yorks
  • Location: Harrogate, N Yorks
    I think perhaps you are posting that with tongue in cheek, as your rather bold statement is a bit thin on factual evidence.

    Mind you it depends on what any of us term as accuracy. very long range lrf is looked upon as accurate if you get the type of airmass correct, trying to predict El Nino or La Nina onsets is even more fraught. Nevertheless the prediction of La Nina, done last year, was sufficiently accurate for both the autumn, winter and spring general weather patterns for the UK to have a fairly accurate prediction by the UK Met Office.

    So as I say, perhaps your comments are done tongue in cheek or possibly to try and wind up one or two posters on here?

    Well yes and no. Forward projections must contain a reasonable margin for error and that margin is cone shaped as any error close in is amplified over time. If you posted a prediction for this autumn with 80% confidence and hit it you'd be pretty proud, so why is 20% margin over a DECADE way out there, especially when we're expected to take these models and make decisions for the rest of the century? Yes, the Met office got it about right on Western Europe this winter, pity absolutely nobody saw the deep freeze that affected the rest of the Northern Hemisphere. Please point me to a post if I'm wrong because I saw nothing about record breaking cold in the US, best skiing season for 20 years, late spring starts. But I do see lots of crap about spring being early in the UK again (despite it still snowing) although I see no evidence for this compared to last year - plants and trees are pretty much in line with where I remember them to come out and the birds and their food have synchronised perfectly in my garden - so I don't expect the mass extinction of blue tits due to lack of caterpillers like what was reported last year.

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    Posted
  • Location: just south of Doncaster, Sth Yorks
  • Location: just south of Doncaster, Sth Yorks

    as someone trying to learn about trying to predict 1-2 months in advance I have to admit I have no idea about the next decade or how accurate any prediction of that or even longer time scale is or may turn out to be. I will not be around much beyond the next decade I suppose once the grim reaper gets my location!

    However, I have never totally believed in either the next Ice Age cometh even though I had the privilege of meeting Hubert Lamb the main supporter of this theory at the Uni he worked from. Nor have I totally believed, in spite of my professional credentials, the idea of GW is all man made. We do not know enough to be able to be sure of that, although increasing amounts of evidence do support that view. What is really without argument is that, for whatever reason the earth has, overall, warmed during the past 100-150 years.

    Again without any convincing evidence to prove it will slow down or stop the consequences of this 50 to 100 years from now are fairly certain.

    Yes, its happened before but with only several thousand people not billions on the earth.

    That is the problem and the effect it will have on the food chain as well as many millions being either drowned or starved to death.

    A bleak prospect and arguing about whether this or that scientific idea is correct is a bit like playing the fiddle whilst the city burns.

    I doubt, even without the effect China and India look like having that we can slow it down much and certainly not stop it but we could start to take decisions to try and alleviate the suffering many many millions before even that is too late.

    sorry, end of sermon, I normally stand back from what are often circular arguments from those with differing views on this forum.

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