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Will IPCC climate models make accurate predictions?

Climatologists have simulated Earth's climate with climate models, which based on physical theories and observations of Earth's past climate, on average predict that adding CO2 to the atmosphere will warm the planet. Skeptics tend to be dismissive of climate models for various reasons, some suggesting the models are extremely uncertain, and others suggesting that systemic biases in the construction of the models leads to outputs that favor warming scenarios.

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Experts and Influencers

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Agree
Experts In Climatology


RealClimate    Climatology Blog
Agree
We discuss climate models a lot, and from the comments here and in other forums it’s clear that there remains a great deal of confusion about what climate models do and how their results should be interpreted. This post is designed to be a FAQ for climate model questions. ... All models show basically the same behaviour that is in line with basic theory and observations.
03 Nov 2008    Source


Gavin Schmidt    Climatologist
Agree
Is Climate Modelling Science? At first glance this seems like a strange question. Isn’t science precisely the quantification of observations into a theory or model and then using that to make predictions? Yes. And are those predictions in different cases then tested against observations again and again to either validate those models or generate ideas for potential improvements? Yes, again. So the fact that climate modelling was recently singled out as being somehow non-scientific seems absurd.
12 Jan 2005    Source

Sub-Arguments Of This Expert:
Have climate models made good predictions so far?
   Mostly Agree

Andrew Dessler    Climatology Professor
Agree
So how do we get a sense of the reliability of climate models? The approach taken by the scientific community is really the only one available: analyze and validate the individual processes in the climate models. ... If you can validate enough processes of the model (water vapor, clouds, ice, oceans, etc.) then you generate confidence that your model is probably making predictions that are at least in the ballpark.
25 Feb 2009    Source

Sub-Arguments Of This Expert:
Is the Anthropogenic Global Warming hypothesis falsifiable?
   Agree

Intergovernmental Panel on Climate Change    (IPCC) Scientific Body formed by U.N.
Agree
There is considerable confidence that climate models provide credible quantitative estimates of future climate change, particularly at continental scales and above. This confidence comes from the foundation of the models in accepted physical principles and from their ability to reproduce observed features of current climate and past climate changes. ... models have consistently provided a robust and unambiguous picture of significant climate warming in response to increasing greenhouse gases.
01 Jan 2008    Source


Disagree
Experts In Climatology


Roy Spencer    Meteorologist
Disagree
Where the IPCC has departed from science is that they have become advocates for one particular set of hypotheses, and have become militant fighters against all others. They could have made their case much stronger if, in addition to [existing models], they would have put just as much work into model formulations that predicted very little warming. If those models could not be made to act as realistically as those that do produce a lot of warming, then their arguments would carry more weight.
23 May 2010    Source


Experts In Science


Denis Rancourt    Physics Professor
Disagree
There is of course much more wrong with state-of-the-art global circulation models (climate models) than the assumption and implementation of CO2-H2O feedback. Although these models are among the most elaborate predictive models of complex non-linear phenomena, they are nonetheless sweeping oversimplifications of the global climate system and its mechanistic intricacies.
27 Feb 2007    Source

Sub-Arguments Of This Expert:
Are climate records (of temperature, CO2, etc.) reliable?
   Disagree

Andrew Monaghan    Meteorologist
Mostly Disagree
This paper provides further evidence that the multi-decadal global climate models are significantly overstating the water vapor input into the atmosphere, and thus are not providing quantitatively realistic estimates of how the climate system responds to the increase in atmospheric well mixed greenhouse gases in terms of the water vapor feedback. This water vapor feedback is required in order to achieve the amount of warming from radiative forcing projected in the 2007 IPCC report.
01 Jan 2008    Source


Robert Carter    Marine Geophysical Professor
Disagree
With the complete discrediting of the ‘hockey stick’ curve of recent temperature change (McIntyre and McKitrick, 2003, 2005; Wegman, Scott and Said, 2006) that was the icon of their report, the IPCC case for dangerous human-caused warming now rests only on ambiguous anecdotal evidence, unvalidated computer models and misleading attribution studies (IPCC, 2007).
02 May 2007    Source


Freeman Dyson    Physics Professor
Disagree
The [climate] models solve the equations of fluid dynamics, and they do a very good job of describing the fluid motions of the atmosphere and the oceans. They do a very poor job of describing the clouds, the dust, the chemistry, and the biology of fields and farms and forests. Many basic processes of planetary ecology are poorly understood. They must be better understood before we can reach an accurate diagnosis of the present condition of our planet.
14 Aug 2007    Source


Patrick Frank    Chemist
Disagree
The claim that anthropogenic CO2 is responsible for the current warming of Earth climate is scientifically insupportable because climate models are unreliable. ... It turns out that uncertainties in the energetic responses of Earth climate systems are more than 10 times larger than the entire energetic effect of increased CO2. If the uncertainty is larger than the effect, the effect itself becomes moot.
01 Jan 2008    Source


Encyclopedia


Conservapedia    Christian Encyclopedia
Disagree
Currently the most advanced climate models, still disagree by more than a factor of two in their sensitivity to greenhouse gas forcing, and have significant disagreements with observed climate behavior at high latitudes. They are, therefore, utterly unable to project the change of climate in response to future greenhouse gas scenarios.
10 Aug 2007    Source


Miscellaneous Experts


Donald DuBois    Computer Modeller
Mostly Disagree
[Models can be misleading, because] underlying assumptions can completely predetermine the results of the model. If the major climate models that are having a major impact on public policy were documented and put in the public domain, other qualified professionals around the world would be interested in looking into the validity of these models. Right now, climate science is a black box that is highly questionable with unstated assumptions and model inputs.
17 May 2007    Source



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0 Points      Terry Oldberg      14 Jul 2010      General Comment
The question "Will IPCC climate models make accurate predictions?" is based upon a false premise. This premise is that the IPCC models make predictions.

The IPCC does not claim that its models make predictions. What it claims is that they make "projections" ( see http://icecap.us/images/uploads/SPINNING_THE_CLIMATE08.pdf ). There is a significant difference between the two.

An IPCC "projection" is a mathematical function that maps the time to the computed average global temperature. A "prediction" is a proposition that states the outcome of a statistical event.

A model that makes predictions is falsifiable, thus lying within science under Karl Popper's criterion for differentiation of scientific from non-scientific models. A model that makes only projections is not falsifiable, thus lying outside science. It follows that the IPCC's advice to the world's policy makers lacks a basis in science.

The IPCC's 2007 report contains a description of the scientific method of inquiry together with the implication that the IPCC follows this method. This implication, however, is false.


0 Points      Benja      15 Jul 2010      General Comment
Thanks for bringing up the issue of falsifiability - you prompted me to add a new question on that specific issue here.

"The IPCC does not claim that its models make predictions. What it claims is that they make 'projections'"
Whether it's a crystal ball or a climate model, if the output tells us something about the future, we have a prediction. Let's not fail to address the issue of falsifiability by getting bogged down in semantics. The climatologist Gavin Schmidt is very representative of the IPCC, and he says in the opening sentence in this article that "There is a simple way to produce a perfect model of our climate that will predict the weather with 100% accuracy.", so if he's using the term "predict", I think that's an acceptable use of the term.


0 Points      Terry Oldberg      17 May 2012      Stance on Question: Disagree
To disambiguate the term "prediction" sufficiently for it to be determined that a prediction has or has not been made is the process that Benja describes as "getting bogged down in semantics." Once we are "bogged down" in this way, it is revealed that the IPCC's climate models do not make what one ordinarily references by the term "predictions."




0 Points      Benja      29 Jun 2010      General Comment
Interesting quote from Roy Spencer: "....[The IPCC should] have put just as much work into model formulations that predicted very little warming. If those models could not be made to act as realistically as those that do produce a lot of warming, then their arguments would carry more weight."

At least he's admitting models are in principle useful! But his suggestion is odd, when you consider that additionally constraining a model to output a desired result can only make it harder for that model to act realistically (i.e. in accordance with all known observations). Essentially he's suggesting that some modelers should assume a future result as part of the input to the model. But isn't that exactly what he's against? It would suggest that modelers should pick and choose elements in the model on the basis of whether it caused a particular metric of the output (i.e. Global Temperature) to be a particular value. But that's backwards. You don't want to assume your hypothesis in the evaluation of whether to accept or reject each element in the model. Roy Spencer is concerned - and that's a good thing - that modelers have an implicit systemic bias in favor of AGW, but his suggestion to build a model that introduces an explicit systemic bias against AGW won't prove anything other than if you're biased you can prove anything.

I agree with Roy Spencer that auditing models for any bias that would favor warming is worthwhile, but I don't think that anyone following Roy Spencer's scientific philosophy will contribute anything useful to this. This comment in his article, which early on advises his readers of the importance to "stick to science rather than hyperbole" reveals why:

"As a result of all this uncertainty, the IPCC starts talking in meaningless probabilistic language that must make many professional statisticians cringe. These statements are nothing more than pseudo-scientific ways of making their faith in the models sound more objective, and less subjective"

Please. Probabilistic language is exactly what we need to make sense of such assessments.


0 Points      Benja      29 Jun 2010      General Comment
Interesting background on the peer-review process for Patrick Frank's article "A Climate of Belief" published in Skeptic magazine, run by Michael Shermer:

Pat Frank says here:

"Michael Shermer then sent [my article] to two further climate scientists of his choice. I was required to respond in detail to their critical comments, and did so. I can tell you as a well-published scientist myself and as an experienced reviewer, that the article went through a very valid peer-review"

Yet, this is what one of those climate scientists, Tapio Schneider, has to say here:

"In September 2007, Michael Shermer, the publisher of the magazine, sent me Frank’s submitted article (an earlier but essentially similar version thereof), asking me what I think of it. This was not a request to review it but an informal email among acquaintances. I pointed Shermer to some of the most glaring errors in Frank’s article. ... After pointing this and other errors and distortions out to Shermer–all of which are common conceptual errors of the sort repeatedly addressed on this site, with the presentation in Frank’s article just dressed up with numbers etc. to look more “scientific” – I had thought this was the last I had seen of this article. ... Indeed, I was surprised by the decision to publish it given the numerous errors."


1 Point      cornwall_5      14 Aug 2009      Stance on Question: Mostly Agree
If one is a firm believer in GIGO (garbage in, garbage out) and that, therefore, computer models are faulty, and specifically that computer models that predict a significant global warming in the 21st century due to humans are faulty, then it also follows that computer models are faulty for proving the opposite point of view: that there is no significant global warming or that humans contribute negligibly. In other words, one is in a "you cannot prove god exists, you cannot prove god does not exist" situation.

I thought I could do a simple search online for computer models that might offer a different prediction than the ones currently recognized internationally, which predict significant global warming caused by humans.

Every time I find any counter website, the website reveals its anti-socialist, pro-capitalism political bias. Moreover, they completely discredit themselves with their irrationality, because they never logically consistently apply the fact that - if computer models are faulty at predicting future - or even past - cause and effect - from some arbitrarily chosen initial condition - and computer models merely include the ideas we humans put into them, then it follows that humans - without the help of computers - are far LESS capable of logically consistently determining cause and effect with their single-variable mind and extremely limited ability to hold massive amounts of data in their memory, compared to a computer.