Talk:General Circulation Model

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Improvement[edit]

WMC, "come on" is not informative as to what is wrong with the following. [1] You've seen the source quotations. (SEWilco 14:53, 20 May 2005 (UTC))

  • "Thousands of climate researchers around the world use climate models to understand the climate system. There are thousands of papers published about model-based studies in peer reviewed journals - and a part of this research is work improving the models. Improvement has been difficult, and progress has sometimes led to discovering new uncertainties."
(William M. Connolley 18:54, 20 May 2005 (UTC)) Rv without understanding wasn't very helpful either. In this case, I reverted without reading your edit, on the assumption that "rv" meant revert. The first change is no great matter one way or another. Adding Improvement has been difficult, and progress has sometimes led to discovering new uncertainties. is more questionable. If you insist on putting it back in, I won't like it, but won't re-remove it for now. Much of the model accuracy section needs a rebalance sometime anyway.
Oh yes, please do improve the models so they are more accurate. Although we won't know until AR4 how accurate the IPCC claims they are for their purposes. (SEWilco 02:30, 21 May 2005 (UTC))

Driver decisions[edit]

This is not true? How did models explain these things? (SEWilco 03:04, 21 May 2005 (UTC))

"The computer models cannot decide among the variable drivers, like solar versus lunar change, or chaos versus ocean circulation versus greenhouse gas increases. Unless they can explain these things, the models cannot be taken seriously as a basis for public policy."

To AOCGM or not to AOGCM[edit]

"Coupled ocean-atmosphere GCMs are used to project/predict future temperature changes under various scenarios."

But the IPCC did not use that? (SEWilco 04:17, 21 May 2005 (UTC))

"AOGCMs can only be integrated for a limited number of scenarios due to computational expense. Therefore, a simple climate model is used here for the projections of climate change for the next century. The simple model is tuned to simulate the response found in several of the AOGCMs used here."[2]

(William M. Connolley 22:30, 21 May 2005 (UTC)) That was Silverbacks mistake, too. Read on. Its obvious that AOGCMs were used. See if you can work out the subtle distinction...

Working from memory, I assume you're referring to the following mention of SRES. I looked at that but didn't spot phrasing which indicated that SRES was the "simple climate model". (SEWilco 04:05, 22 May 2005 (UTC))
(William M. Connolley 13:11, 27 May 2005 (UTC)) I'm baffled. What are you talking about? SRES are scenarios.
LOL Citing only the hottest A2 scenario is a bit biased isn't it, and calling the 1% compound CO2 concentration business as usual is also stretching NPOV. Hans Erren 20:57, 24 December 2005 (UTC)
You need to laugh less and study more... 1% is clearly labelled "idealised"; A2 isn't the hottest, is92a is used as well... William M. Connolley 21:25, 28 December 2005 (UTC).

I just did, see below,

'The A2 scenario is characterized by a politically and socially diverse world that exhibits sustained economic growth but does not address the inequities between rich and poor nations, and takes no special actions to combat global warming or environmental change issues. This world in 2100 is characterized by large population (15 billion), high total energy use, and moderate levels of fossil fuel dependency (mostly coal). The A2 scenario is the most well-studied of the SRES scenarios that assume no attempt to address global warming.'

A near tripling of world population? Ever heard of Lutz? ref: Wolfgang Lutz, Warren Sanderson & Sergei Scherbov, 2001, The end of world population growth, Nature 412, 543-545, 2 aug 2001 [3]

I prefer, for climate model intercomparison, the pure mathematical 1% compound CO2 concentration rise over any SRES storyline. BTW the graph [4] is called Global_Warming_Predictions.png. I suggest to change it (and the graph title) to "Climate model intercomparison". Hans Erren 22:20, 4 January 2006 (UTC)

Good grief, I may agree with you here... firstly, that graph has on itself the correct word "projections" and the graph itself should probably be moved to G_W_projections rather than intercomparison. Put a note on the talk page there to be polite. I'm really note sure quite how important the variouis SRES stuff is... its better to just rescale from a time axis to a CO2 axis, which to first order works. William M. Connolley 23:37, 4 January 2006 (UTC).

Not with my approval[edit]

(William M. Connolley 13:16, 27 May 2005 (UTC)) SEW added some stuff, apparently because he thought I recommended it. I'm not sure exactly what he meant, but I regard most of what he added as badly phrased and pretty much POV pushing (the POV being anti-model). So I've removed it.

rm flat planet[edit]

SEW wrote: many models are based on a flat planet. This is so bizarre that I don't know what he meant, but its wrong. William M. Connolley 09:23, 12 Jun 2005 (UTC).

Many models have been based on a flat planet. An example above, "1.25 degrees in latitude and longitude", uses a grid with the characteristic that grid areas become much smaller and closer together closer to the poles as lines of longitude converge. Conversely, there is less resolution around the climatically significant areas near the Equator. The first model to use a geodesic grid was announced in 2001. [5]
  • I mentioned one example of a grid with a spacing of "1.25 degrees in latitude and longitude". In what way do its lines of longitude not get closer together toward the poles? (SEWilco 15:22, 12 Jun 2005 (UTC))
(William M. Connolley 19:21, 12 Jun 2005 (UTC)) Of course they get closer towards the poles. What has this got to do with a flat planet?

rm history of conv param[edit]

I've removed:

Convection parametrization was found to be necessary in the 1950s, as climate models otherwise became unstable after simulating a few weeks. Akio Arakawa's widely used solution was to ignore loss of kinetic energy and enstrophy. Although ignoring some basic physical behavior, the technique has been widely used in order to get results which resemble what is expected. [6] [7] [8]

Most of this is history of GCMs, which doesn't belong there.

Of the bits that *aren't* history but are current, its impossible to determine. Current models do (I think) conserve KE, so leaving it in is misleading. And... the refs in the AMIP table... don't mean that the exact Arakawa 1972 scheme is being used. People tend to ref the paper when doing a brief description and not ref local improvemnts.

Also, the AIP page is a bit... mystical in that section. I slightly wonder if Weart is a bit out of his field there.

  • A little background seems appropriate rather than just saying "Arakawa's computational trick is in use". (SEWilco 14:51, 12 Jun 2005 (UTC))
  • Any sources that current models do conserve KE? (SEWilco 14:51, 12 Jun 2005 (UTC))
(William M. Connolley 19:26, 12 Jun 2005 (UTC)) You have abstracted, with no real understanding, a small fragment from the AIP history. This *isn't* the history of climate models page, please don't try to make it so. Start a page on that if thats what you want. The only reason you've dumped this in here (with absolutely no idea whether or not any of this is still current) is because it looks slightly dodgy. Please try to give up the instinctive septicism. Is A's "trick" still in use? You don't know. What is the trick? HYou don't know. Do models conserve KE? Models go to great lengths to conserve quantities that should be, so the default is, yes they do, unless you've got good evidence otherwise.

Getting into this one a bit late. The AIP page is hopeless, a mish-mosh of allusions to aliasing (not named as such) and quadratic-conservative schemes. In the real world KE cascades from larger to smaller scales and eventually is dissipated at the scale of molecular viscosity, which of course is too small to represent in a GCM. The unresolvable part of the cascade is instead mimicked by viscosity-like terms that dissipate KE in the smallest resolvable scales. Raymond Arritt 04:51, 7 July 2006 (UTC)

rm van Dorland[edit]

I removed:

Rob van Dorland, lead author of the IPCC report scheduled for release in 2007, stated "Truthfully, we are far from knowing with certainty how natural climate factors, such as volcanic eruptions and solar activity, affect the earth's climate" [9].

From the context, its clear that this statement isn't really about the *accuracy* of the models - its about the Hockey stick stuff. Also, the source is distinctly dubious: essentially propaganda.

Parameters[edit]

There is a link to parametrization which redirects to Coordinate System which does not seem very relevant. I think linking Climate parameters, forcings and feedbacks is more relevant. However I am not happy with the quality of the page. Perhaps William Connolley could use his expertise to improve it then change the link.

Hmm yes. I've moved (and heavily edited) Clim param... to Parametrization (climate) and will change the link to that. William M. Connolley 18:57:55, 2005-07-31 (UTC).

Error Found in Models[edit]

I'm not sure how recent this China Daily article's information is, but it portends badly. Into Global Warming I inserted the paragraph "In December, 2005 it was revealed the reflectivity effect of airborne pollutants was about double that previously expected, and that therefore some global warming was being masked. This effect implies that pre-2006 models will underpredict future global warming. [10]" However, I feel that more detail is merited in this article. Does somebody get Nature? Simesa 20:56, 28 December 2005 (UTC)

I've seen this. I would always prefer to let things settle in the literature for a while, for all but the most definite results. This one has the potential to be less exciting than it seems, but its hard to be sure at this stage. William M. Connolley 21:39, 28 December 2005 (UTC).

Follow-up: I contacted a researcher (Jerry Meehl) at NCAR: He replied that, as WMC suggested, the new estimates are within the uncertainty bands for models being used ror the next IPCC report. (I wasn't aware that China had supercomputer-model capability.) Specifically, the researcher said:

The exact magnitude of various forcings is uncertain. The new estimates you refer to for aerosols are larger than what some models use (the magnitude of what models compute, for example, for sulfate aerosols varies depending on the nature of their sulfur cycle models or types of sulfate aerosol concentrations they use) but not out of the range of uncertainty for aerosol forcing used across all of the more than 20 models currently being assessed in the IPCC AR4. This accounts for some of the range of model responses to the simulation of 20th century climate. Even with this uncertainty in aerosols, the GHGs are still the largest forcing by far, and are the big driver for late 20th century warming and estimates of 21st century warming. The latest simulations will be assessed in the IPCC AR4, but many modeling groups are publishing their latest findings in the peer reviewed literature now (for example, from our group see: Meehl et al., 2005: How much more warming and sea level rise? Science, 307, 1769—1772).

Simesa 18:59, 29 December 2005 (UTC)

Para to talk[edit]

I've rm'd:

Accurate predictions of climate effects due to solar forcing and its associated feedbacks are important to prediction of effects due to anthropogenic greenhouse gas emissions, because models which fit observed temperature data but underestimate effects due to solar forcing will overestimate effects due to anthropogenic greenhouse gases, and vice versa.

This para is somewhere between wrong and misleading. If models underestimate solar forcing, then they are likely to underestimate other forcing as well; so underestimating solar is just as likely to lead to underpredicting future change. It also (I think) rather misrepresents the D+A stuff. See-also http://www.realclimate.org/index.php?p=229 (and the comments) William M. Connolley 21:39, 28 December 2005 (UTC).

Techncal template[edit]

I've added the Technical template to this article largely because of the part under "A rather more complete discussion of climate models is provided by the IPCC TAR chapter 8, Model Evaluation (2001)." It really doesn't make much sense out of context, and needs cleaned up. Calion | Talk 06:41, 21 February 2006 (UTC)

Predictive value?[edit]

Have there been examinations of the predictive value of climate models? I'm pretty sure that early models were around in 1990, say, so how well did their predictions accord with the change in climate over the past 15 years or so? "Postdiction" of facts known to the people who made the model isn't a terribly impressive achievement, I would say, and it surely isn't a good measure of how well the model will predict the future. —Simetrical (talk • contribs) 20:45, 12 March 2006 (UTC)

Not a lot, because the question isn't as sensible as it appears. People run coupled GCMs starting in about 1860 ish (for a variety of reasons) so thats not a good test of the 1990-now timeframe, because they aren't constrained at 1990. There is some stuff by Hansen in 1990 predicting to now; I think that came out OK though can't remember the ref. Also climate models aren't supposed to predict year-to-year variability William M. Connolley 20:52, 12 March 2006 (UTC)
What kind of time scale is more suitable to test the validity of a climate model? Are any other tests being performed (and links if possible)? Can any model claim to have any predictive value without being properly tested? I agree that creating outputs that match past data well should not at all be considered the same as making reasonable predictions of the future, even if it is very difficult and based on valid science. Why wasn't the above question as sensible as it appears? TheQuickBrownFox (talk) 15:11, 6 November 2009 (UTC)
Hansen's 1988 predictions overestimate global warming. Try a google image search for "hansen 1988 prediction". I suspect that WC is very aware of this.
He considered 3 scenarios and only Scenario 3 - a rapid decline in greenhouse gas emissions around the year 2000 (which didn't happen) - comes close to the actual temperatures recorded. Since this decline in gasses did not happen, this scenario prediction is also a failure in the same direction as the others (overestimating warming).
It would be reasonable and balanced to mention the failure of past climate models when considering the predictive value of current ones.
194.81.49.122 (talk) 11:53, 30 August 2011 (UTC)

Relation to weather forecasting[edit]

Cleaned this part up a bit. Also removed the tangential comments on analog forecasting and such. That material could be appropriate for an article on history of weather forecasting but has no relevance to GCMs. Raymond Arritt 03:42, 8 May 2006 (UTC)

S+H 2003[edit]

I've cut this to talk:

As recently as 2003, Sun and Hansen were calculating and using flux corrections and parameterization of cloud models to achieve cold start of a simulation based on "the assumption that the planet was in radiative balance in 1951".

because I dont know what it means. There is some mixing of flux corr and clouds? William M. Connolley 19:24, 17 June 2006 (UTC)

you should read the article. parameterization of the cloud model was used to achieve the flux correction.--Poodleboy 15:07, 19 June 2006 (UTC)
Um. And you think that will make sense to the reader of the article? The text already says *most* recent models don't use FC; so listing *one* that does (and not even telling us which model it is) doesn't make much sense. I haven't read the article; it shouldn't be necessary, to understand what you are on about. I suggest that if you really want the text in (and I can't see what it gains you) you need to make it comprehensible. So... they are using FC; but they weren't using the normal method, they were including the clouds? (were calculating and using flux corrections and parameterization of cloud models doesn't mean what you're now saying; if you mean param of clouds (clouds are always param!?!) was used to generate the FC... then I'm still baffled) In what way? Do tell William M. Connolley 15:36, 19 June 2006 (UTC)
OK, reading the paper: Ocean A is imposed SSTs, so no FC. We apply no flux adjustments with ocean E because such nonphysical adjustments can have a significant effect on the simulated climate (Neelin and Dijkstra 1995; Tziperman 2000). And ocean B has imposed horiz fluxes, which is FC. So this is a sensitivity study on different models... your text is misleading for that alone. And I don't see your point about the clouds... please quote chapter and verse William M. Connolley 15:36, 19 June 2006 (UTC)

grids[edit]

I took out:

The grid can either have a fixed resolution, or can be specified as a gaussian grid, where the latitude resolution is not constant.

Its confusing as written (many people will interpret "fixed" and "constant" as meaning in time). Its also wrong, in implying that this exhausts the possibilities: as mentioned later, its perfectly possible to have a grid with any variation in latitude. What I think it means is that FD models tend to use constant-spacing and Spectral ones use gaussian... William M. Connolley 08:18, 21 September 2006 (UTC)

Okay, I sort-of see why you have removed this twice. This section of the article is about grids, and I feel that it is worthwhile to mention some common grid types, such as gaussian grids (e.g., NCEP-DOE reanalysis 2, CCCma, ECMWF). I'm not a climate modeler, but I was very confused when I first encountered NCEP's fixed and gaussian grids about 1/2 a year ago. So I read up on them and created the gaussian grid article to help me, and others, understand what they are. To me, it would be more confusing to not mention a few common grid types, as they are encountered by non-climate modelers. Certainly, there are many types of grids, such as polar, etc, and these do not need to be described here, as they are very climate modeler niche material — better suited in technical books and journal literature rather than Wikipedia. Much of the content in this article is very technical by nature, so I don't feel that adding a mention of a few common types of grids would contribute to much more confusion. Also, I was sure to specify "latitude" when using "constant", thereby reducing the confusion with other dimensions (such as time). +mwtoews 20:44, 21 September 2006 (UTC)
Maybe I was too harsh. Sorry. How about the current version? BTW: re NCEPs grids: as I understand it (and I'm sure of this for ECMWF) there is the "native" grid (which is gaussian; and indeed reduced-gaussian to boot) which is actually used by the physics. Then there are various other grids - 2.5 degrees, say - onto which the output can be interpolated William M. Connolley 21:41, 21 September 2006 (UTC)
Perfect, I think that is all that is needed, thanks. I thought that the "native" grid would have been the gaussian grid, but I was never really sure until now. +mwtoews 21:56, 21 September 2006 (UTC)

New Paper[edit]

Anyone see this: New Study Increases Concerns About Climate Model Reliability. How does this get worked into the article and is the full paper out yet? DJ CreamityOh Yeah! 20:45, 11 December 2007 (UTC)

I don't think its out yet. I do think the paper is dodgy (here for my opinion) William M. Connolley (talk) 21:21, 11 December 2007 (UTC)
Yeah, but thats a blog .... we cant use it, right? DJ CreamityOh Yeah! 21:45, 11 December 2007 (UTC)

Koutsoyiannis Et Al[edit]

I would like to add this new peer reviewed and published scientific paper concerning the predictive power of climate models. http://www.atypon-link.com/IAHS/doi/abs/10.1623/hysj.53.4.671

The data on page 9 is of particular importance. I know original interpretation is not allowed and I will find a credible source for that.

The data is very obvious, however, as the correlation numbers are absurd. —Preceding unsigned comment added by Mickeyklein (talkcontribs) 19:45, 3 August 2008 (UTC)

Wikiproject Earth[edit]

Hello i have recently proposed the Wikiproject Earth. This Wikiproject`s scope includes this article. This wikiproject will overview the continents, oceans, atsmophere and global warming Please Voice your opinion by clicking anywhere on this comment except for my name. --IwilledituTalk :)Contributions —Preceding comment was added at 15:34, 30 March 2008 (UTC)

page has wrong title[edit]

This page should be titled 'General Circulation Model'. —Preceding unsigned comment added by 216.165.95.70 (talk) 01:37, 10 January 2009 (UTC)

Why? William M. Connolley (talk) 12:24, 10 January 2009 (UTC)
Yes, there is already a page on climate models, so this page should concern itself with the general circulation model, which is a component of a climate model. That would both be more correct than merging the two pages. Eric Salathe (talk) 18:37, 23 January 2009 (UTC)
Indeed, at first sight the article needs to split up, one specifically about general cirulation models (GCMs), and one about climate models. Since there already is an article about climate models, the best approach in my opinion is to move a large part of this article to the Climate Model article (and remove redundant parts). Note that even though there is some ambiguity in literature about the term GCM (general circulation model vs. global climate model vs. some variants), in the scientific literature GCM means "general circulation model". Therefore I also agree with anonymous. Hulten (talk) 10:22, 21 February 2011 (UTC)
I also agree, and since most recent discussion seems to agree, I have moved the page to "general circulation model" and updated links pointing to "global climate model." The "climate model" page is preserved as the page concerning global climate models in general, while this page is reserved for general circulation models in particular. Redirects from pages seeming to search for climate modeling in general, specifically "Climate change modeling" and "Climate change model," have been changed to direct to "Climate model." Beezorphlegmon (talk) 22:01, 2 February 2014 (UTC)

weaknesses section[edit]

I've added this http://en.wikipedia.org/wiki/Global_climate_model#Weaknesses_of_Global_Climate_Models Needless to say, WMC reverted all my work without attempting to improve it. Please can people look at the text i added (try history if it's been axed again) and comment/improve on it. Andrewjlockley (talk) 15:11, 6 April 2009 (UTC)

"Needless" to say that he reverts you... Perhaps you should reflect a bit about why he reverts you. (and why i just did the same)
Could it be:
  • Bad representation (to direct misinterpretations) of references?
  • Undue weight?
  • One sided focus?
  • Original research?
etc etc? --Kim D. Petersen (talk) 15:25, 6 April 2009 (UTC)
Same as it ever was. Short Brigade Harvester Boris (talk) 15:27, 6 April 2009 (UTC)
I'm not disputing it needed improvement, I'm asking for something constructive that I can work with - not just blanking everything I've added. The list above is just a scattergun criticism with no effort made to apply it to the actual text. How am I supposed to actually work with that? Andrewjlockley (talk) 15:43, 6 April 2009 (UTC)

I think the problem is that you don't understand the material you are adding. Your "model" of the situation is, or appears to be from the outside, "fling stuff at the article and hope someone will fix it up". Our model is "if people add stuff that is wrong, remove it, and ask them to discuss on the talk page before they re-add it". You now have a solid repuation for failing to understand the references you add, so no-one trusts your refs to actually support what you say. Your task is to force us to revise this reputation William M. Connolley (talk) 15:47, 6 April 2009 (UTC)

Another thing you need to work on is structure and logical order. You have a history of plopping material into articles without regard to context or flow (again, presumably because you don't understand it well enough to gauge how different aspects of a topic relate to one another). So not only do we have to fix your references, and fix your prose, we have to figure out the right place for it. It's not reasonable to demand that of other people. Short Brigade Harvester Boris (talk) 16:09, 6 April 2009 (UTC)

The entire thing was badly broken. This bit Carbon cycle modelling, notably the impact of climate change on methane clathrates and methane stored in permafrost.<ref>Harvey, L. D. D., and Z. Huang (1995), Evaluation of the potential impact of methane clathrate destabilization on future global warming, J. Geophys. Res., 100(D2), 2905–2926.</ref> is perhaps the most obvious - but please don't assume from that I mean the rest of reasonable. Most carbon cycle models do ocean carbon, and soil carbon, and some representation of vegetation. I don't think anyone does oceanic clathrates (probably because it would be dull: the ocean is too cold to release them, and will stay that way for a while) in GCMs and I don't think anyone does permafrost carbon but I could well be wrong about the latter. If anyone *is* doing it, it wont be in a ref from 1995. Without a doubt that ref (which I haven't read, any more than AJL has) says nothing about what happens when you add MC to GCMs William M. Connolley (talk) 21:09, 6 April 2009 (UTC)

The reason I added that reference was that they attempted to do some basic modelling of MC. I'll use another reference (perhaps referencing permafrost modelling) as that's probably a better example. Now, what else needs cleaning up before the section gets rebuilt? Guys, I really value your advice and help and comments - I just wish you could be a bit less brutal with the editing when you give it. I'm not here to mess up WP, and whilst my edits are rarely perfect they aren't usually complete drivel either. Andrewjlockley (talk) 21:46, 6 April 2009 (UTC)
New section seems to address a lot of these concerns.Andrewjlockley (talk) 23:18, 29 April 2009 (UTC)

Weart[edit]

Might use http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6VH6-50S8C4F-1&_user=870092&_coverDate=09%2F30%2F2010&_rdoc=4&_fmt=high&_orig=browse&_origin=browse&_zone=rslt_list_item&_srch=doc-info%28%23toc%236058%232010%23999589996%232436735%23FLA%23display%23Volume%29&_cdi=6058&_sort=d&_docanchor=&view=c&_ct=11&_acct=C000046800&_version=1&_urlVersion=0&_userid=870092&md5=44592835a9247366ae32ffba471562f6&searchtype=a someday William M. Connolley (talk) 11:30, 5 October 2010 (UTC)

Merge - argh[edit]

I've just noticed [11], which appears to "merge" (actually, copy - the original is still there) text from Climate model. I'm not at all convinced that made sense.

In the course of which, I notice that Climate models are systems of differential equations based on the basic laws of physics, fluid motion, and chemistry. To “run” a model, scientists divide the planet into a 3-dimensional grid, apply the basic equations, and evaluate the results. Atmospheric models calculate winds, heat transfer, radiation, relative humidity, and surface hydrology within each grid and evaluate interactions with neighboring points. is at http://celebrating200years.noaa.gov/breakthroughs/climate_model/welcome.html, though they may have copied us. That text came in [12].

William M. Connolley (talk) 11:42, 5 October 2010 (UTC)

Referencing the above post, Gobal Climate Models do not "calculate" winds, etc. Those are affected by convection and other latent heat factors such as precipitation which are "estimated". The estimates are in turn applied to parameters, which in fact are not parameters of the real world at all, but only of the model. To actually "calculate" those factors would required computational ability in excess of what is available at this time, as although the phyusics is known, the grid sizes are much too large to accurately reflect reality, especially in terms of increased heat retained at the surface which would alter convection, precipitation, etc. Stevehhll (talk) 16:20, 17 October 2010 (UTC)

Artificial initial conditions.[edit]

Why do you object to indicating that the climate models begin from an artificial (i.e. human constructed even if they are based on data) set of initial conditions? --The great sluggo (talk) 21:09, 22 October 2010 (UTC)

Because if they are based on data, they are not artificial. We aim for WP:NPOV, and the word "artificial" would suggest that general circulation model results are fake. Awickert (talk) 21:25, 22 October 2010 (UTC)
You seem to have a misunderstanding about the definition of artificial. Please follow the link. The reality is that the initial conditions are first and foremost a man-made construct (even if in some sense they were derived from some natural measurements) which means that the term artificial is the appropriate one to describe them. They most certainly are NOT a natural formation or construct. Are you truly suggesting that they are?
Nothing in that statement suggests that the models are fake and the fact remains that they are inherently an artificial construct including their initial conditions.
Please suggest an acceptable wording to make the above point clear to the reader. --The great sluggo (talk) 21:48, 22 October 2010 (UTC)
Followed the link, and the word is still unacceptable ("false, misleading"). "The initial conditions are parameterized from field data" would be acceptable. Awickert (talk) 22:14, 22 October 2010 (UTC)

Edit request from Stevehhll, 26 October 2010[edit]

{{edit semi-protected}} In the phrase: "Atmospheric models calculate winds, heat transfer, radiation, relative humidity, and surface hydrology within each grid and evaluate interactions with neighboring points.]]"

Please change "calculate" to "estimate" because grid sizes are too large to realistically calculate those factors, so they are parameterized or affected by parameters. The parameters are artificial inputs to the model. They are not calculations, so it is logically incorrect to say those factors are "calculated". They may be calculated in the model, but to say they are calculations of real world physical processes is inaccurate.

Thank You. Stevehhll (talk) 10:12, 26 October 2010 (UTC)

Stevehhll (talk) 10:12, 26 October 2010 (UTC)

I think this is an edit that was tried but reverted the other day. I'm not innately opposed to this but I'd need to see examples of this terminology in use by modelers themselves (and since it's been called into question, the same applies to the word "calculate"). While I recognise the distinction and I would use verbs like "estimate", "approximate", "simulate" or even just plain "model" in describing the computed numerical components of my own (non-climatological) models, I'd like to see what the terms of art are used in climate modeling. Tasty monster (=TS ) 16:29, 26 October 2010 (UTC)
Not done: please establish a consensus for this alteration before using the {{edit semi-protected}} template. -Atmoz (talk) 16:51, 26 October 2010 (UTC)

Reorganization and additions[edit]

A history section was added, which was mostly from the recently-upgraded numerical weather prediction article. The section of GCM, within the GCM article, was giving the article the look of a nesting doll, so content from this section was subdivided between the history, computation, and accuracy sections. Thegreatdr (talk) 01:12, 9 January 2011 (UTC)

Title–lead sentence mismatch[edit]

Given that this article's title is "Global climate model", it's confusing to have the opening sentence of this article begin, "A General Circulation Model (GCM) is a mathematical model of the general circulation of a planetary atmosphere or ocean...". I would encourage someone familiar with the subject matter to rewrite the lead to introduce the term "Global climate model" before "General Circulation Model". - dcljr (talk) 19:57, 21 June 2011 (UTC)

I believe that this is part of a bigger issue, namely that the initialism GCM is used for this page that is mostly about global climate models (or Earth system models). The original meaning of GCM is General Circulation Model. I have tried to put this information under "Note on nomenclature" in the article. This clarifies the issue on GCM somewhat, but for the page as a whole it may be confusing. I'd suggest a separate page on General Circulation Models (GCMs), the models that describe circulation (chiefly AGCM and OGCM) and not things like interfaces (e.g. air-sea), chemistry and biology. Hulten (talk) 11:42, 13 May 2013 (UTC)

Inhofe on accuracy?[edit]

I removed the last sentence from the Accuracy section...

Forecasts of climate change are inevitably uncertain. Even the degree of uncertainty is uncertain, a problem that stems from the fact that these climate models do not necessarily span the full range of known climate system behavior. [13]

... with an edit summary of "Removed "...Even the degree of uncertainty is uncertain..." statement. Inhofe does not satisfy WP:RS on the topic"diff. This was reverted with an edit summary of "rv unexplained removal of text" diff. I'll bite. When did The Facts and Science of Climate Change by U.S. Senator James M. Inhofe become more than a WP:PRIMARY source for the political opinions of Inhofe? Without a better source the statement cannot remain. - ArtifexMayhem (talk) 06:54, 27 August 2011 (UTC)

It's undoubtedly true, but I agree, it cannot remain. — Arthur Rubin (talk) 13:49, 27 August 2011 (UTC)

IPCC citations.[edit]

There is a wide spread pattern of deficiences, inconsistencies, and inaccuracies present in most existing citations of the IPCC AR reports. I have developed a replacement set of complete, verified citations, which can be seen at Global warming. If there are no objections I propose to appy them to this article. - J. Johnson (JJ) (talk) 23:40, 12 September 2011 (UTC)

Yes I had noticed that too. Its a lot of work. Great idea. Go ahead. Good on you. Mrfebruary (talk) 01:08, 13 September 2011 (UTC)
Done. I have also tagged several "citations" that consisted of a mere URL (or URL+title). In an article as high-level as this, with such a preponderance of editors with serious scientific experience, I am surprised that there is any tolerance of such a shoddy practice. A citation needs to identify the source, not just point to where the text is found on the Web. This includes the author(s) or organization behind it, and identifying information such as ISBNs or DOIs. Otherwise the material is not sourced. Hopefully someone will fix those soft spots. _ J. Johnson (JJ) (talk) 19:03, 15 September 2011 (UTC)

Reference for study[edit]

Anyone wanting to study this topic furhter might want to see "A Vast Machine" by Paul Edwards, reviewed in Science (14 Jan. 2011, p. 149). ISBN 9780262013925 ~ J. Johnson (JJ) (talk) 21:44, 27 October 2011 (UTC)

Climate sensitivity[edit]

I am baffled by the results listed under zero-dimensional models. How in the world could the temperature be twice as sensitive to albedo as it is to incident intensity? This is clearly an error. Geoffrey.landis (talk) 21:04, 30 January 2012 (UTC)

Confuses Climate Models with Circulation Models[edit]

This article is confusing, because it uses the acronym GCM to mean both "General Circulation Model" and "Global Climate Model", and it is the article that is reached by searching for either term. I attempted to clarify this a little.

The structure is a little odd as well; it starts out with the most complicated models, and then after many screens of complicated models, without warming switches to discussing very basic models. I tried to clarify this by putting in a new heading "Simplified Models of Climate", and putting all the models that previously had their own headings as subheadings under this.

I will also note that as far as I can tell, the text here is cut-and-paste identical to the text in the Wikipedia Climate model article, even to the extent of including the same climate sensitivity error. Why do we have this material here? These aren't circulation models. Can't we just link to the Climate model article?

I would suggest renaming this article "General Circulation Model", and making the term "Global Climate Model" redirect to the Climate model article. Geoffrey.landis (talk) 21:32, 30 January 2012 (UTC)

Yes, but then all the non-GCM things (i.e. everything that is not either an ocean general circulation model or atmospheric general circulation model, without interfaces, chemistry and so on) should be removed from this article on General Circulation Models (GCMs). Hulten (talk) 11:47, 13 May 2013 (UTC)
I agree, and believe that these should be removed. There is little value in including descriptions of zero-point and other models in this article unless in the background section, as there is significant overlap with the page on climate models in general. I suggest removing the entire section "Simplified models of climate." Beezorphlegmon (talk) 08:00, 9 February 2014 (UTC)

Proposed Rename[edit]

I did a google search, and found 1.15 million hits for the search term gcm "general circulation model", 307 thousand hits for the search term gcm "global climate model", and 329 thousand hits for the search term gcm "global circulation model." It seems pretty clear that GCM is used to mean "general circulation model" much more than that other uses of the phrase.

Therefore, I propose renaming this page "General Circulation Model," and redirecting "Global climate model", and "Global circulation model" here. Geoffrey.landis (talk) 20:01, 2 February 2012 (UTC)

I agree for the most part. Following your reasoning, we should indeed rename it to "General Circulation Model" (and maybe redirect "Global circulation model" to this page. However, a global climate model is something else and is already pretty well described in the page Climate model, so I'd refer it to that page. Hulten (talk) 11:54, 13 May 2013 (UTC)


any comment on recent nature climate paper on model accuracy[edit]

Overestimated global warming over the past 20 years, J C Fyfe et al, Nature Climate Change, vol 3, page 767 (2013) Their Figure one suggests that climate models dramatically overpredict temp rise; this is in contradiction to http://www.ipcc.ch/pdf/assessment-report/ar4/wg1/ar4-wg1-chapter8.pdf — Preceding unsigned comment added by 24.91.51.31 (talk) 01:53, 14 October 2013 (UTC)

Agree Accuracy section needs to be rewritten to reflect scientific data. In particular, it must be noted that despite the positive review of climate models (currently discussed in the article) in 2001, more than 95% of them have proven incorrect a decade later. A good figure for inclusion would be something along the lines of http://wattsupwiththat.files.wordpress.com/2014/01/clip_image013.jpg ALso references http://www.dailytech.com/After+Missing+5+Predictions+IPCC+Cuts+Global+Warming+Forecast/article33457.htm In the end these are supposed to be scientific models, subject to falsifiability. Mrdthree (talk) 02:55, 10 July 2014 (UTC)
You can't use the Torygraph, or WUWT, as a source for science William M. Connolley (talk) 08:01, 10 July 2014 (UTC)