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All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.

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Climate Hustle

How reliable are climate models?

What the science says...

Select a level... Basic Intermediate

Models successfully reproduce temperatures since 1900 globally, by land, in the air and the ocean.

Climate Myth...

Models are unreliable
"[Models] are full of fudge factors that are fitted to the existing climate, so the models more or less agree with the observed data. But there is no reason to believe that the same fudge factors would give the right behaviour in a world with different chemistry, for example in a world with increased CO2 in the atmosphere."  (Freeman Dyson)

Climate models are mathematical representations of the interactions between the atmosphere, oceans, land surface, ice – and the sun. This is clearly a very complex task, so models are built to estimate trends rather than events. For example, a climate model can tell you it will be cold in winter, but it can’t tell you what the temperature will be on a specific day – that’s weather forecasting. Climate trends are weather, averaged out over time - usually 30 years. Trends are important because they eliminate - or "smooth out" - single events that may be extreme, but quite rare.

Climate models have to be tested to find out if they work. We can’t wait for 30 years to see if a model is any good or not; models are tested against the past, against what we know happened. If a model can correctly predict trends from a starting point somewhere in the past, we could expect it to predict with reasonable certainty what might happen in the future.

So all models are first tested in a process called Hindcasting. The models used to predict future global warming can accurately map past climate changes. If they get the past right, there is no reason to think their predictions would be wrong. Testing models against the existing instrumental record suggested CO2 must cause global warming, because the models could not simulate what had already happened unless the extra CO2 was added to the model. All other known forcings are adequate in explaining temperature variations prior to the rise in temperature over the last thirty years, while none of them are capable of explaining the rise in the past thirty years.  CO2 does explain that rise, and explains it completely without any need for additional, as yet unknown forcings.

Where models have been running for sufficient time, they have also been proved to make accurate predictions. For example, the eruption of Mt. Pinatubo allowed modellers to test the accuracy of models by feeding in the data about the eruption. The models successfully predicted the climatic response after the eruption. Models also correctly predicted other effects subsequently confirmed by observation, including greater warming in the Arctic and over land, greater warming at night, and stratospheric cooling.

The climate models, far from being melodramatic, may be conservative in the predictions they produce. For example, here’s a graph of sea level rise:

Observed sea level rise since 1970 from tide gauge data (red) and satellite measurements (blue) compared to model projections for 1990-2010 from the IPCC Third Assessment Report (grey band).  (Source: The Copenhagen Diagnosis, 2009)

Here, the models have understated the problem. In reality, observed sea level is tracking at the upper range of the model projections. There are other examples of models being too conservative, rather than alarmist as some portray them. All models have limits - uncertainties - for they are modelling complex systems. However, all models improve over time, and with increasing sources of real-world information such as satellites, the output of climate models can be constantly refined to increase their power and usefulness.

Climate models have already predicted many of the phenomena for which we now have empirical evidence. Climate models form a reliable guide to potential climate change.

Mainstream climate models have also accurately projected global surface temperature changes.  Climate contrarians have not.

Various global temperature projections by mainstream climate scientists and models, and by climate contrarians, compared to observations by NASA GISS. Created by Dana Nuccitelli.

There's one chart often used to argue to the contrary, but it's got some serious problems, and ignores most of the data.

Christy Chart

Basic rebuttal written by GPWayne


Update July 2015:

Here is a related lecture-video from Denial101x - Making Sense of Climate Science Denial

Additional video from the MOOC

Dana Nuccitelli: Principles that models are built on.

Last updated on 31 December 2016 by pattimer. View Archives

Printable Version  |  Offline PDF Version  |  Link to this page

Further reading

Carbon Brief on Models

In January 2018, CarbonBrief published a series about climate models which includes the following articles:

Q&A: How do climate models work?
This indepth article explains in detail how scientists use computers to understand our changing climate.

Timeline: The history of climate modelling
Scroll through 50 key moments in the development of climate models over the last almost 100 years.

In-depth: Scientists discuss how to improve climate models
Carbon Brief asked a range of climate scientists what they think the main priorities are for improving climate models over the coming decade.

Guest post: Why clouds hold the key to better climate models
The never-ending and continuous changing nature of clouds has given rise to beautiful poetry, hours of cloud-spotting fun and decades of challenges to climate modellers as Prof Ellie Highwood explains in this article.

Explainer: What climate models tell us about future rainfall
Much of the public discussion around climate change has focused on how much the Earth will warm over the coming century. But climate change is not limited just to temperature; how precipitation – both rain and snow – changes will also have an impact on the global population.

Update

On 21 January 2012, 'the skeptic argument' was revised to correct for some small formatting errors.

Comments

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Comments 1051 to 1100 out of 1107:

  1. NorrisM @1047 , if I may add some background to Tom Dayton's posts :-

    When considering climate models, it is well to remember that the models are based on the physical realities of this world.

    And the most basic of relevant points, is that the natural greenhouse effect from CO2 etc. has been "artificially" (anthropogenically) pushed higher by the addition of fossil-origin CO2 to the atmosphere.  The result is that the world is warming up — it is gaining heat at the rate of approx. 2 watts per square meter.  (Which may not sound very much : yet if you think it through planetwide and decades-long, then it represents a major problem for this planet.)  Also, if you think it through (regarding where that heat is going and how it moves about within the system of the planet) then you will realize that a pause or hiatus is simply not possible until such time as the system eventually reaches equilibrium (in 2 or 3 centuries' time).

    Therefore if Koonin says there is a real "Hiatus", then he talks nonsense.

    If you are a Black-Letter lawyer, you will wish to examine "fake-skeptic" comments without considering their provenance or any ad-hominem aspects.  Yet as a pragmatic man-of-the-world lawyer, you will wish to take into account the background information regarding the four protagonists you mentioned [Koonin, Christy, Curry, Lindzen], when you come to assess their evidence.

    And you will be aware of human frailties — particularly that frailty called "Motivated Reasoning" : where even very intelligent people (such as Koonin) do bend their rationality and end up deceiving themselves.  And doing so, very staunchly!  And with apparently honest demeanor!

    Climate science is a large area, where you can educate yourself considerably — and if you do so, you will find yourself in agreement with the extensive and almost unanimous consensus of experts (e.g. the U.S. National Academy of Sciences; the U.K. Royal Society; the Vatican's Pontifical Academy of Sciences; and dozens more of peak scientific bodies).  All in consensus about Global Warming.  Indeed, there is only a score or so of Koonins, Christys, Currys, and Lindzens who hold an outlier position in disagreement with the overwhelming preponderance of scientific experts.  And as you yourself gain education in climate science, you will understand that these 4 protagonists, despite their intelligence, have all managed to make a very poor judgment of the actual position.  And that, as you look beyond their rhetoric, you will find that their apparently scientific arguments are empty and false.

    How is it possible for 4 intelligent people to be so very wrong?  It is because their emotions have pushed them into motivated reasoning.  Motivated reasoning by Koonin / fundamentalist religious bias from Christy and Lindzen / and something less clear, from Curry [about whom you need ask: Cui Bono ].

    In the strictest sense, these four are not being scientists — because they have allowed their emotions to override their dispassionate intellects.

    They have muddied the waters and confused your understanding of the significance of models (and of the physical realities).

  2. NorrisM @1047,

    A big long comment from you setting out a lot of stuff. Can I home in on the things you describe as "what also troubles me in everything that I have read so far on climate change." (As you say it is off topic for the thread but...)

    (1) The Mediaeval Warm Period. This you describe as being "at least 200 years in at least Greenland and Northern Europe close to or equal to our present temperature." The temperature at the top of Greenland can be reconstructed from ice cores with some accuracy. GISP2, for instance shows results like this graph and some will take the last few thousand years of this graph as proof that recent warming is trivial when compared with previous centuries, as this SkS post describes. Yet the most recent GISP2 data dates from 1855 and when you graft on modern temperature data things look a whole lot different. The idea that Greenland experienced temperatures "close to or equal to our present temperature" is not borne out by the evidence.

    2. "During the 1600's and 1700's there was ... skating on the Thames." We do have the CET Central England Temperature record stretching back into the 1600s, temperatures recorded a few dozen miles up the road from the Thames at London. This shows seriously cold winter month have been occuring occasionally throughout the record with the last occuring in 2010. History tells us that Ice Fairs were rare events and they do coincide (almost always) with these exceptional cold CET months.  Ice Fairs stopped not because of a Little Ice Age ending or because of global warming but because the old London Bridge was demolished and the banks of the river were embanked. It's all a bit nerdy, but ancient accounts of the Thames freezing continue back in time and continue through the Mediaeval Warm Period (prior to the bridge being built) and are even found for the centuries called by some the Roman Warm Period.

    3. You are on much safer ground suggesting that reconciling the temperature record and climate forcing in the first half of the 20th century is not straightforward but very much less safe with the so-called hiatus. There is a lot of comment on these elsewhere within the SkS site. You do raise the idea that if the hiatus was the product of La Nina sucking the warming from the atmosphere and down into the ocean depths. (It is not controversial to state that the years 2007-13 saw lower global temperatures due to La Nina and withut these years the so-called hiatus is truly a non-event.) From this you speculate whether it was potentially the oceans warming the atmosphere 1975-98. You are not the first with such speculation. Bt if there was such a warming from the oceans, there would be evidence of it in the Ocean Heat Content data as it takes a lot of heat to both warm and keep warm the atmosphere. The level of heat required would certainly have to be evident in the OHC data. It is not evident.

    Response:

    [PS] Thanks for contribution but it would be more appreciated if you had followed the request to put it on the correct place since MWP is offtopic here.

  3. Tom Dayton, Eclectic & MA Rodger.  I would like to thank all of your for your comments.  I think I have to spend more time reading the full thread  both for this topic as well as on questions of MWP etc.  I think that I will withdraw from any further comments until I have at least read the full thread on this topic (this could be a long time!). 

    As a lawyer and not a scientist, I find the best way to come to a conclusion is listen to both sides similar to the process in determining any litigation (I am actually a business lawyer not a litigator).  For this reason, my plan is to stay on this website and also the Nigel Lawson GWPF site.   I actually have never even looked at the Skeptical Science website.  I think I can "filter" things sufficiently to read postings on both sites.

    The information on Steve Koonin is quite interesting given his statements in the transcript of the APS panel hearing where he professes surprise a number of times on what he was hearing.  I thought I was reading the questions of independent physicists who were trying to get at the facts (I just about said "truth").  But I do commend that transcript to all of you, if only to hear how  these significant IPCC climatologists respond to the questions. 

    But one suggestion to the editor of this website.  I think that "ad hominen" comments on the persons contributing to this website should be fully deleted and never appear at all on the website.  Just "stroking them out" but allowing everyone to read them just encourages those kind of comments to be made.  I do find that the proponents of anthropogenic global warming seem to be much more in "attack mode" than the other side.  Can we not come up with a less pejorative term than "climate change denier" with all its connotations when literally none of the Curry, Christy et al group deny that the world is getting warmer.

    This term "fake skeptic" is awfully close to "fake news".  Is it recently invented since the advent of Trump?

    Having said all of this, the recent post today indicating that Stephen Hawking is onside and part of a new organization gives me a significant degree of comfort.  Reading his History of Time was a challenge but I got through it.  Unless I have missed another YouTube, I was very disappointed with the Neil DeGrasse Tyson video explaining global warming because it is so simplistic and does not explain any of the challenges in trying to "predict" future changes in the climate.   I appreciate why he has done this, reaching for the lowest common denominator amongst the public, but I think scientists do have a responsibility to qualify absolute statements.  Otherwise, they move into the political arena which then undermines the confidence the public has in their scientific statements.

    In any event, thanks very much for all of your comments.  Lots of reading ahead of me.

    Response:

    [DB] "This term "fake skeptic" is awfully close to "fake news".  Is it recently invented since the advent of Trump?"

    The term "fake-skeptic" has been used in this venue since at least 2010.  The denial of the science by the venues you note is well-established over the years.

    [PS] Your "truth search" understandably seems to be about determining the reliability of witnesses. How many bits of GWPF propoganda, misinformation and denial would we have to demonstrate to you before you decided they were unreliable witnesses?

  4. NorrisM

    Firstly, for you as a lawyer, whose principle skill is the use of language...

    "Can we not come up with a less pejorative term than "climate change denier" with all its connotations when literally none of the Curry, Christy et al group deny that the world is getting warmer."

    This is standard rhetorical technique which I presume you would be adept at slicing through in a legal context. The term 'climate change denier' covers a range of differing 'denials' and by claiming it is being ascribing to one subset of of this 'population', aren't you are engaging in rhetoric.

     

    Next, the purpose and function of climate models. They are, really, no different from weather models. Used to produce the weather forecast.

    Climate models work at a coarser resolution than weather models but essentially attempt to produce differing results. A weather model takes what the weather is today and attempts to determine what the weather will be x days from now. In principle, exactly. Well, sort of...

    A climate model, being coarser, has a snowflakes chances in hell of doing this. One run of a climate model will be significantly random. And another run of a climate model, with slightly differing starting conditions will also be significantly random.

    What if we do many runs of the climate model, each with slightly differing starting conditions? Each run is different. But what does the average of many runs look like? Well this starts to have a pattern, an order to it.

    Although each run differs, their average is much less chaotic. Because the underlying climate does vary in a modestly predictable way. The average has predictability.

    But that does not mean that the actual day to day evolution of weather over climate timescales will accurately follow this average trend. Because day-to-day weather is chaos superimposed over an underlying order. And since we can't easily predict the chaotic component, the actual weather data will not ever match the climate exactly.

    So we can't expect weather to progress with the regularity that the climate averages suggest.

  5. NorrisM:

    With a legal background, and experience in trying to assess the credibilty of different sources, one thing for you to look for is inconsitencies in a position. Skeptical Science has a summary page listing contradictions in the so-called "skeptical" view of climate change.

    Another issue to keep track of is how often someone expresses complete certainty on something. Generally, you will find that the science of climate change has a lot of "ifs" and "most likelys" - sources of error are discussed at length, and implications of uncertainty are noted. In the so-called "skeptical" view, you will often find very definitive statements (that often contradict other definitive statements). In science, admission of uncertainties is a strength, not a weakness.

  6. Response to NorrisM's comment on another thread: Norris wrote "If I understand your first example, this would suggest that it is appropriate to "average" the various model results and compare them with the actual observations."

    No. There is only one observation run, so you cannot average it with other observation runs to obtain the observations mean, so you cannot compare the models mean to the observations mean. Instead, you compare the observations run to the statistics of the model runs, including not just the model runs mean but the model runs spread.

    Likewise, we have only one observations run of Earth's temperature because we have only one Earth. You continue to ignore my explanation from weeks ago. As MA Rodger noted, in that comments thread you have merely reiterated your claims from this thread without responding here to the people who gave you information you asked for. 

  7. Also following from NorrisM's comment on the thread Tom Dayton refers to:

    The model spread is also not an ideal representation of the uncertainty in the prediction, because the number of models is very limited and the type of things they include is different.

    RealClimate has set up a page that discusses such things in more detail.

  8.  NorrisM @that other thread,

    In the context of seeing the results of Multiple Linear Regression adjustment to the global temperature record (Foster and Rahmstorf (2011) adjusting for Sol, Vol & ENSO), you ask:-

    "I do not know if you are able to do this but if you were to elimate both the 1998 El Nino and the 2015-2016 El Nino from the data, how would the models stack up to actual observations excluding those events?"

    The linear assumption for temperature response in F&R2011when Sol,Vol&ENSO are accounted for does leave much unaccounted for while the models in accounting for actual forcings and climatic responses and so have no problem with the 'non-linear', but in so doing fail to reproduce the very important but unpredictable ENSO oscillations.

    One approach to coping with ENSO unpredictability adopted by Risbey et al (2014) is to be selective of the model results and only include "those models with natural variability (represented by El Niño/Southern Oscillation) largely in phase with observations are selected from multi-model ensembles for comparison with observations."

    And the finding - "These tests show that climate models have provided good estimates of 15-year trends, including for recent periods and for Pacific spatial trend patterns."

    Another approach adopted by Huber & Knutti (2014) is to calculate the adjustment required to account for ENSO effects in the models. They conclude from this work "that there is little evidence for a systematic overestimation of the temperature response to increasing atmospheric CO2 concentrations in the CMIP5 ensemble."

  9. Clarifying MA Rodger's excellent reply to NorrisM: Risbey et al.'s approach demonstrated that the models do a good job of producing the sizes and durations of ENSO events. What the models do a poor job of is getting the timings ("phasings") right. Possibly the models never will get better at that, no matter how powerful the computers. Part of the reason for that shortcoming is that climate models are not intialized with the conditions yesterday in order to project the conditions tomorrow. Weather models do that, which is why weather models solve the "initial values" problem. In contrast, climate models are initialized with conditions far enough in the past so that by the time they get to projecting the future, the weather has canceled itself out, thereby wiping out any preferential effect of their particular choice of initial values. What constrains climate models to converge on their long run statistics regardless of their initial values, are the "boundary conditions" of the climate system, such as the net energy entering/leaving the top of the atmosphere. See the post on weather versus climate. After you read the Basic tabbed pane there, read the Advanced tabbed pane, and be sure to watch the video there.

  10. Responding to comment by Mike from here

    Further to that - when modellers run one of projections for what humans will do (the RCPs which are about emissions, aerosols), they also have to put in what they think natural forcings will be. (Sun, volcanoes). These are not predictable. If you didnt put in some volcanic eruptions, then the models would always run to hot. However, modellers cannot actually predict when, where, or how big an actual eruption will be - so you put representative volcanic aerosols based on average past history, and vary that with runs. Solar is also hard to tie down precisely.

    So if your interest is how well a particular model predicted climate 10 years ago, it is better to rerun the identical code but with actual forcings not the what was projected at the time. This will tell you how well the model will predict climate as opposed to how well modellers predicted forcings. Unless you are pseudoskeptic of course - if so then any distortion that backs your ideologically-based prejudices is just fine, by ideology beats reality, right?

  11. My two cents worth. I'm not a scientist, and not a lawyer, but I have done some stage 1 introductory level university maths, chemistry, physical geography,  in the 1980's.

    The comments 1054 - 1059  above on models are of course perfectly correct, but would be hard for a lawyer or total lay person to understand.

    I would simplify or maybe summarise comments by saying models can predict long term temperature trends, and endpoints, because greenhouse gases and basic, underlying long term solar changes can be quantified as a long term trend. Models cannot predict every wiggle along the way, because ocean processes are slightly random in their timing. These wiggles might be a couple of years or up to ten years, but they don't alter the basic long term trend or track.

    This is how I have explained things to denialists. If I'm wrong please tell me.

    The pause was significant, but by the time it was properly measured, it was not outside of what models predict could happen.The "pause" looks about 8 years maximum in the nasa giss graph. Models have error bars partly to allow for this short term, random, natural variation.

    If you look at the model / real world data comparisons on realclimate.org the models are predicting temperatures over the last 30 years pretty well. 

    Temperatures are slightly 'under' but not by much, and are certainly within error bars. 

    The more useful question is to ask why  are models still slightly over estimating temperatures. I have read a theory that oceans are delaying warming a little.

    Anyway if you look at the realclimate graph, it obviously wouldn't take much for temperatures to jump towards the very top of the error bar.

    The bottom line is it seems absurd to me to claim in 2017 that models are way off, or anything like that. Therefore scientists claiming this are grand standing to make inflammatory statements. I dont think that really helps, as it gets picked up by the media.

  12. Also following along the question of removing El NIno effects from the observational record, a simper appraoch is to look at only the years with El Nino, only the years with La Nina, and the remaining "neutral" years as different data sets. Examining the trend in each set individually will help separate the effects in a much simpler manner than the multiple regression or modelling techniques. The simplicity may make it easier to understand.

    This has been done by John Nielsen-Gammon, and SkS posted on this in this discussion:

    https://skepticalscience.com/john-nielsen-gammon-commentson-on-continued-global-warming.html

    Short story: all three sets show basically the same trend.

  13. Thanks everyone above. 

    Nigelj, I have to admit that 1054-1059 are challenging for a lawyer.  I have not had time to go to realclimate.org but I will after we return from holidays.  On our sailboat and hoping for wind but I have to admit, I do turn the diesel engine on when there is no wind! 

    To me the issue of how close the models match observations over whatever necessary period (20 years?) is critical.  The "other side" says that there are large discrepancies (I believe that is what they say).  If anything, a Red Team Blue Team approach would be the opportunity to show the other side what the models can and cannot do over specified periods of time and how accurate they are.  As I noted elsewhere, Santer and Held had the chance to make this point at the APS panel and now have Koonin questioning the models because they did not adequately defend them.

    My simplistic understanding of the scientific method is that one comes up with a theory and tests it to see if it is borne out by the tests.  Or the model makes predictions and one looks back to see if the models were correct. 

    If the models cannot show that they are accurate over a 10 year period, then it does get problematic because how are public officials expected to commit massive amounts of funds until the models have shown that it is reasonable to assume they are right on, for example, a 3C rise by 2100 assuming that it is "business as usual"?  When I use "predict", I mean a model projection which assumes that no mitigation is taken.

    One last point before I head off.  I do not think we can rely on "hind casting" to prove that the models can closely match reality because there are too many "fudge" factors used to make the models "fit" the actual history.  There is no way of knowing if the same fudge factors work for the future.  This is not original, I know. I think this is Freeman Dyson's comment  at the beginning of this thread. 

    i will certainly spend more time on this when I get back.  Perhaps by then we will have heard what the Trump administration has decided to do.  If all we get is a TV debate as suggested by Scott Pruitt then all we will get is a gong show.

    I truly think that a scientific debate along the lines of a legal hearing with both sides going at each other with an independent panel coming to a decision (with dissenting opinions) would be the best way to achieve some form of acceptance by the Republican party.  I know this sounds naive but I have to admit I would like to see it!

     Moderator:  Sorry, just a little "off topic" at the last.  Sometimes it does not make sense to fully "stream" these thoughts.

    I am very much still a "fence sitter" on this issue because it is so technical and you have intelligent human beings on both sides of this debate saying different things.  It is very frustrating.  You would think that everyone could at least agree on the facts.  Perhaps the Red Team Blue Team traditional approach could achieve some agreement on at least how far apart the models are from observations.  That is why I so much trust our adversarial system of justice in Canada and the US compared to the European system.  Let each side go at it and have an independent judge or judges render their decision AND provide their reasons for their decision.  If there is disagreement amongst the panel, then dissenting opinions are also given.

    Response:

    [DB]  "If the models cannot show that they are accurate over a 10 year period"

    As Tom Dayton notes, you continue to ignore the explanation he gave you even earlier.  You also continue to not investigate the links you were given.  You  instead resort to sloganeering (repeating claims already invalidated).  In a judicial trial, a judge would warn you for this behaviour.  In this venue, there is a similar reproach.

    Please note that posting comments here at SkS is a privilege, not a right.  This privilege can and will be rescinded if the posting individual continues to treat adherence to the Comments Policy as optional, rather than the mandatory condition of participating in this online forum.

    We really appreciate people's cooperation in abiding by the Comments Policy, which is largely responsible for the quality of this site.
     
    Finally, please understand that moderation policies are not open for discussion.  If you find yourself incapable of abiding by these common set of rules that everyone else observes, then a change of venues is in the offing.

    Please take the time to review the policy and ensure future comments are in full compliance with it.  Thanks for your understanding and compliance in this matter.

  14. NorrisM @1061 , several points :-

    1.  Yes, you are beyond even the most extreme naivety, if you feel there's a chance that the political extremists [= Republicans, in this case] would come to any "acceptance" of what the climate science is telling us.   And I'm sure that you, as a man of the world, are aware of the situation.   It doesn't matter how many hearings occur, at ever higher levels of review and appeal, all the way up to the Supreme Court or beyond . . . . . the extremists will reject authoritative judgment (even if it were issued by the Archangel Gabriel).

    2.  The Global Warming issue has already already been "Red-Teamed and Blue-Teamed" extensively, for many years — and the result is as you know, a unanimous decision by the only court truly competent to make the judgment (i.e. by the scientists who have the technical knowledge to make the properly-informed decision).  Yes, not quite strictly unanimous : there is a minuscule group of "dissenter" climate scientists [ well under 1% ] but their decisions are incompetent owing to the incoherent and mutually contradictory assertions they make.  (And a realistic cynic would regard these "few" as composed of crackpots and/or shills for vested interests).

    3.  The politicians who reject & deny the plain scientific truth, will only change their viewpoint if it seems imminent that they will be voted out by a "fed-up" public — or if their major donors die off or themselves succumb to public pressure (e.g. to shareholder revolt).   It is the long-running propaganda campaign of denial, which is the actual influencer or "hamperer" of public opinion : and not any judicial decision or series of judicial decisions.

    4.   NorrisM, let us be realistic : the question of virtuosity of "models" is unnecessary to the scientific case.   The real physical world has already given us the decision, by means of obvious and incontrovertible evidence — sea levels have risen and are rising ever faster; planetary temperature has already risen 1 degreeC above the previous [downward] trend; glaciers and polar ice and permafrost are disappearing at a rapid & increasing rate; the oceans have warmed & acidified; plants and animals have changed their traditional pattern of activity.

    Crackpots & shills try to delude themselves and deceive us with graphs which are downright economical with the truth [to use that ironically polite phrase!!].    But in summary :- the world is clearly rising significantly higher in temperature, and with no sign of slowing down any time soon — so to that extent "models" are unnecessary for responsible policymakers (and for us ordinary citizens, too).

    Reckless foolhardiness & negligence are the traits of the "deniers".

  15. Correction : that should be addressed to NorrisM @1063.

    My apologies for that typo.

  16. Regarding modelling. Even if you forget models, just for one minute, and just project the last 30 years trends forward as a linear trend to end of century, you get very significant warming.

    However it will then only take a quite small acceleration to this recent trend, due to constant ramping up of emissions combined with proven positive feedbacks, to cause more warming of about roughly 4 degrees. (Sort of like compound interest). This is what people need to get their heads around.

    The Red Blue team court room concept  is not the appropriate mechanism to decide science. Courts are already having huge problems making sense of complex financial cases, that are beyond judges, juries and lawyers. Repeating this exercise for science is verging on insanity.

    You would be deciding the fate of the planet on who is the best dressed most articulate, and possibly devious speaker and gut reactions of people to all this. Its better to leave such decisions to the people at the IPCC and their more measured processes.

    The Europeans grasp this problem and have more of an "Inquisitorial" legal system for complex cases. The  IPCC  system that we already use is essentially an inquisitorial system!

    Honestly I cannot believe the absurd lenths the Republican Party are going to try to deny the climate problem.  If only they could see themselves from the outside looking in, and how absurd and desperate they look.

  17. NorrisM,

    To me the issue of how close the models match observations over whatever necessary period (20 years?) is critical.

    as a lawyer then, perhaps I could ask you whether a person should be judged on the basis of what they have clearly stated (and is recorded), or on the basis of what someone else has reinterpretated them to say?

    What climate science expects, is that surface temperature will evolve as a very wiggly line that mostly lies within the range of the multiple model runs ( the grey area in the model projection maps).

  18. Also, I wonder that put so much emphasis on prediction. Models beat reading entrails hands done, but they are not best way to test climate theory, especially such a noisy variable as surface temperature. The normal physics verifications are much better but funnily enough, not skeptic talking points.

    Closer to my speciality, I am glad  people can take the necessary expensive reforms required from taking earthquake science seriously without demanding prediction models match observations exactly first. Good thing ideological biases havent got in the way there.

  19. I have an important challenge for all climate scientists who feel mathematically inclined.

    According to modern climate science theory, H2O vapor concentration is determined only by temperature. This is because H2O can exist on earth in all three phases (solid, liquid, or gas), and therefore the concentration of H2O vapor is determined by the Clausius-Claperyon (C.C.) equation at the given temperature. CO2, however, exists on earth only as a gas (except of course for man-made dry ice), and therefore is subject to no such constraints by the C.C. equation.

    The fact that CO2 concentrations can freely vary whereas H2O vapor concentrations are determined by temperature makes CO2 a "control knob" for the greenhouse effect. The argument is that we can increase CO2 concentration without it condensing, which would then increase greenhouse heating causing a rise in temperature. This temperature rise then causes more H2O molecules to enter the vapor state which in turn causes more GH heating. The reverse, of course, holds true if CO2 concentrations decrease. Therefore, CO2 controls the GH heating even though H2O vapor is the stronger GHG, both spectrally and in quantity.

    In examining the derivation of the C.C equation, we note that it assumes an isolated system in thermal equilibrium, which the earth and its atmosphere is not. They do, however, form a local thermal equilibrium (LTE) system where temperature and concentrations can be defined locally but not globally, a situation often occurring in fluid mechanics. To a climate scientist, LTE works the same as global equilibrium for use in the C.C. equation. I have some misgivings about that but I won't argue the point now.

    Let's take a look at the C.C. equation. It states that for an isolated system consisting of a substance in the gas state in thermal equilibrium with the same substance in the liquid (or solid) state, the partial pressure P of the gas is related to temperature T according to

    ln (P/P_ref) = (H_vap/R)((1/T_ref) - (1/T))

    where P_ref and T_ref can be any known valid partial pressure / temperature pair, for example P_ref = 1 atm at T_ref = 373 deg K, H_vap = latent heat of vaporization, and R = universal gas constant. Notice that only one value of the partial pressure P and one value of the temperature T is inserted into this equation. So, how do we choose those values for a system consisting of many different partial pressures and temperatures? I believe most climate scientists would say that one merely replaces the values of P and T with their global mean values

    and . But is this mathematically correct? This is the challenge I have for all climate scientists who feel mathematically inclined. Given that the above equation is true for all points on the globe (ie. LTE is assumed), prove or show a counter-example to this equation:

    ln (

    /P_ref) = (H_vap/R)((1/T_ref) - (1/))

    Keep in mind, of course, that if this assertion is not true, then the entire CO2 "control knob" theory is in serious trouble.

    Response:

    [DB] Sock puppet nonsense snipped.

  20. Randy C @1069, your assumptions about what climate scientists believe are in error.  In particular, while the assumption of constant relative humidity is used as a first approximation of the water vapour feedback, it is not used as an assumption in detailed explorations of the issue.  See Minschwaner an Dessler (2004) as an example of more detailed examinations.

    I will further note that your assumption that if relative humidity is not maintained, the water vapour feedback is negligible is also not valid.

    Response:

    [DB] Please note that RandyC is just the latest iteration of serial spammer cosmoswarrior and his iterative sock puppets coolearth / diehard / dieharder / moonrabbit / landdownunder / blackhole / WhiteDwarf / GreenThumb / HeatRay / RobJones / JamesMartin / banbrotam / JeffDylan / jcdylan.  His compulsion to flood this venue with sock puppets is strong, bordering on pathological.

  21. RandyC - would you accept that if climate science is correct about CC control of water vapour, then Total Precipatible Water should then be highly correlated with surface temperature? Furthermore, you agree that if climate science has it wrong about CC, then climate sensitivity derived from paleotemperature archives would be lower than those derived from models?

  22. scaddenp - Let us consider your first question

    Would you accept that if climate science is correct about CC control of water vapour, then Total Precipatible Water should then be highly correlated with surface temperature?

    The short, simple answer to your question, of course, is "yes". Given a certain temperature, there is one and only one value of the H2O vapor concentration that satisfied the CC equation. Equivalently, we may regard the CC equation as establishing the H2O vapor concentration as a function of the single independent variable T (ie. temperature). This being the case, we would expect that the amount of H2O vapor in a column of air above a certain area on the surface to be closely tied to the temperature of this area on the surface.

    There is also, however, another implication if the CC controls H2O vapor. Remember that the CC equation was derived to determine the equilibrium partial pressure (or equivalently concentration) of a vapor when a reservoir of this same substance in the liquid or solid state is present. This equilibrium concentration (determined by the CC equation) also plays the role of a saturation concentration whether any liquid H2O is present or not. The idea is that if the vapor concentration exceeds this saturation value, then liquid H2O will precipitate until thermal equilibrium is once again established between the H2O vapor and liquid present. Therefore, the CC determines the maximum vapor concentration at a given temperature and not the vapor concentration at this temperature. If we use the CC determined H2O vapor concentration as the atmospheric H2O vapor concentration, the implication would be 100 percent relative humidity everywhere. This would preclude deserts or otherwise dry climates anywhere. Also, the H2O vapor feedback, established as the principal mechanism of AGW, would be way overestimated.

    ---------------------------------------------------------------

    Moderators - In posting this message, I am not spamming, trolling, nor being a "sock-puppet". I am merely responding to a question specifically directed to me by scaddenp @1071. By definition, spamming and trolling are unsolicited messages which this is not. Now I don't care if you want to delete this paragraph, but please leave everything above it intact. If you object to me posting any messages whatsoever, you will need to take it up with those commentators asking questions directed at me in their postings.

    Response:

    [DB] This is yet another (of almost 2 dozen) iterative sock puppet of serial spammer cosmoswarrior.  Posting rights rescinded, per Comments Policy.

  23. Recommended supplemental reading:

    The most accurate climate change models predict the most alarming consequences, study finds by Chris Mooney, Washington Post, Energy & Environment, Dec 6, 2017

    The Most Accurate Climate Models Predict Greater Warming, Study Shows by Georgina Gustin, InsideClimate News, Dec 6, 2017

    Both articles describe the findings contained in:

    Greater future global warming inferred from Earth’s recent energy budget, Patrick T. Brown & Ken Caldeira, Nature 552, 45–50 (07 Dec 2017)
    doi:10.1038/nature24672

  24. John,

    That article is so sad :(.

  25. From reading the article that John Hartz linked free copy it appears that Norrism has been half right about climate models.  They have been systematically incorrect.  Unfortunately, they have underestimated the expected warming, not overestimated the warming as Norrism suggested. From the discussion:

    "Finally, it is sometimes argued that the severity of model-projected global warming can be taken less seriously on the grounds that models fail to simulate the current climate sufficiently.  Our study confirms important model-observation discrepancies, indicating ample room for model improvement.  However, we do not find that model errors can be taken as evidence that global warming is over projected by climate models.  On the contrary, our results add to a broadening collection of research indicating that models that simulate today's climate best tend to be the models that project the most global warming over the remainder of the 21st century." (my emphasis)

    This is not the first evidence that models under-project future warming.  We are in deeper doo-doo than we thought.

  26. michael sweet @ 1075

    "We are in deeper doo-doo than we thought."

    On this point, the Economist article on "negative emissions" did not provide any "percentage" measurement as to how much reliance the climate models have placed upon the withdrawal of CO2 from the air compared to reductions in present emissions.  Are we talking 20% for the assumed contribution from "negative emissions" or more than that?  Can someone point me to where this has been discussed? 

    It clearly was not it in the Chapter 9 of the Fifth Assessment. 

    I have to admit that after reading Chapter 9 in its entirety and the admitted problems discussed in that chapter associated with the uncertainties caused by trying to simulate cloud processes and their feedbacks in the models that I have personally decided to focus my climate education on actual observations of temperature increases and sea level changes (including the impact of melting ice in Greenland and the Antarctic) representing the two of the most significant effects of AGW. 

  27. NorrisM @1076,

    You ask "Are we talking 20% for the assumed contribution from "negative emissions" or more than that?"

    I ask "20% of what?"

  28. Norrism:

    Since I currently live in Florida and come from California I will suggest you add stronger storms (especially higher precipitation and hurricanes) and a longer fire season with bigger fires to your list of significant effects of AGW. 

    A drought linked to AGW was one of the prime causes of the Syrian civil war.  The fall of the Egyptian government was partially due to increased bread prices due to drought in Russia that caused their harvest to fail.  That drought was AGW linked.

    The widespread failure of farming is probably more significant in your lifetime than sea level rise (and my lifetime although I have friends  in Tuvalu and own land in Florida).

  29. MA Rodger @ 1077

    I admit that my question was not well-posed.  I went back to the Economist article and realized that I had missed their more detailed discussion of negative emissions at page 20.  What I was trying to get a sense of is how significant is the problem of not having proven negative emission technologies (NETs) in place.

    I appreciate that measuring this as a percentage is difficult in that we are really looking at what carbon budget we have left if we wanted to stay below 2C and what amount of CO2 has to be sucked out of the atmosphere.  But the numbers are significant.  My understanding is that we are presently pumping about 40 bn tonnes of CO2 into the atmoshere and that, according to this Economist article, we need to take out 810 bn tonnes by 2100 to have a reasonable chance of staying at 2C by 2100.

    But if CarbonBrief.org is correct, we can only pump into the atmosphere another 800 bn tonnes of CO2 if we want a 66% chance of staying under 2C by 2100.  On their website they correctly show that at the present rate we run out of our remaining "carbon budget" in 20 years.

    So I agree that my question was confusing.  But this is an astounding amount.  The negative emissions required by 2100 represents 100% of our remaining carbon budget we have if we want to have a 66% chance of staying below 2C.

    Based upon the chart on page 21 of the Economist, by 2100, the negative emissions have to represent approximately 20 bn tonnes per year to match the 20 bn tonnes per year of remaining CO2 and other emissions to arrive at a net zero emission level.

    I think I have this right.  I am sure you will correct me if I am wrong.

  30. michael sweet @ 1078

    I hear what you are saying but I do not want to get into issues such as whether AGW is causing more intense hurricanes (what happened between Katrina in 2005 and Irma et al in  2017?).  Clearly the IPCC states that we will have more droughts and more precipitation.  I fully accept that.

    As for residents of Florida and California, there is a certain amount of "caveat emptor".  You do not buy land near an airport and then complain about the noise of jetliners.  Everyone who can afford expensive real estate in Florida and California can afford insurance to protect them from these risks.  No question there are other areas of the world where this is not the case but again, this is an issue that Bob Loblaw and I discussed at length (on some other thread) and I personally do not want to revisit it.  We have both stated our differing positions. 

    But even at this last meeting in Bonn we have seen what has happened to the climate fund for developing countries.  Politicians are good at talking but when it actually comes to coming up with cash out of their national budgets it is a different thing.   We even now see China and India coming back to the table with the old theme of saying that a disproportionate share should be contributed to this fund by the developed countries because of past CO2 contributions.   Back to the drawing board it seems.

    Moderator.  I appreciate this is getting off topic.  Just wanted to reply to michael sweet on his additions.

  31. NorrisM @1079.

    WIthout checking the figures you quote, do be aware that it is not CarbonBrief who set out the carbon budget you quote; it is IPCC AR5 simply with the used emissions budget being subtracted.

    And perhaps to give some indication of the sort of figures your comment seems to be aiming at, the figure from Anderson & Peters (2016) here suggests a value of  perhaps 600Gt(CO2) by 2100.

    And do note this comment is verging on being off-topic.

  32. I hold that it is a mistake to call the effects of fossil CO2 emissions "Climate Change". For a start, it is too mild. The effects could be Catastrophic Climate Change.
    But my point, with respect to models, is that climate modelling is far more difficult than the simple thermodynamic equation that was contained in the warning of Svante Arrhenius, about a century ago.
    For several millennia, except for the occasional huge volcanic eruption, the temperatures on Earth, or as we might more usefully call it "within the biosphere" remained within a range to which the living organisms had evolved to accustom themselves.
    Arrhenius showed that the thermodynamic balance between radiation received and radiation emitted depends upon the temperatures of terran surfaces being such as to emit radiation, mostly infrared, that balances what has to escape plus that which is recaptured by gases that turn it into their own kinetic energy, and share that.
    Arrhenius showed that carbon dioxide was indeed remarkably capable of capturing infrared radiation of exactly the range that comfortably warm and not-too-cold surfaces emit.
    It is a simple step from there to conclude that a rise in proportion of CO2 from 280 ppm to 400 ppm, which is today well documented, will cause the biosphere to accumulate heat annually at some rate that eventually gets it "warm" enough to emit more energetic infrared.

    The danger is that since the cause of the problem is that accumulation, but the rate of its manifestation is the rate at which snows and ice can melt, and entire oceans can warm, lots of people and even governments may fail to be convinced, until it's too late.

  33. michael sweet

    Here is my comment which was snipped for being off-topic.  

    I think the real difference between what I will call the "warmists" versus the "luke warmers" is not really a difference on the science. Both sides accept that the planet is getting warmer and CO2 emissions constitute at least 50% of the warming (with the difference largely related to whether there are 60 year oscillations of the AMO). The real difference between the warmists and the luke warmers is a disagreement on the ability of the models to accurately predict what will happen after 2050. 

    But is that not what this all comes down to? We cannot agree on: 1. whether the temperature increases in RCP 8.5 are realistic based upon the limited ability of the models to replicate the climate 50 years into the future; and 2. whether the assumptions of fossil fuel use in RCP 8.5 are realistic. As well, all the "scary stuff" in the models seems to take place from 2050 onwards so we really cannot even point to any spectactular  failure of the models today. The models are not falsifiable because we have to wait 30-50 years.

    It is true that Einstein's theory of relativity was only "proven" many years later (I cannot remember the comet's path which seemed to prove it correct) but in that case the world was not asked to change its source of energy over a relatively short time period given that presently approximately 85% of our energy needs are provided by fossil fuels and less than 5% by wind and solar power.

    Response:

    [DB] Sloganeering and blatant handwaving snipped.  Either bring actual credible evidence to support your contentions or acknowledge that these assertions by you are simply your uninformed opinions.  A number of posts at SkS already detail the accuracy of model projections vs actual performance (like herehere and here).  Indeed, there is a plethora of posts examining just how well models as far back as even the 1980s and 1970s have performed.

    Models and observations

    BEST Model performance

    CMIP3 models are spot-on

    CMIP5 models are spot-on

    You are welcome to make your case using actual evidence.  You are not welcome to spread misinformation or to represent your opinions as anything other than that (opinions); without credible evidence to support them, they will be disregarded and dismissed if they differ from established science and scientific research.  I'm not going to bother to warn you further as the fact is: you've been given ample warnings and simply ignored them.

  34. Your "luke warmers" used to argue that there was no warming.  They changed their hats when it became impossible to continue with their past lies.  They continue to lie to the public about the changes expected from warming.  Look at the briefs submitted to the court by deniers in the case of young people suing the government.  You cannot concede the possibility of sea level rise contained in the US Climate Change report which is described by its author as "very conservative".

    The real difference between warmists and luke warmers is that the luke warmers are deliberately lying to the public about the dangers we face.

    The models can be falsified in myriad ways.  You are just making excuses.  The problem is that you are listening to oil company lobbyists and not scientists.  There is much more than temperature modeled.  We can compare the models to ocean heat, atmospheric humidity, rainfall patterns, drought predictions, extreme storm predictions, floods, temperature changes in different areas, river flow, and many more.  All these data points give us evidence of the accuracy of the models. 

    We already see the stronger storms, drought, flooding and sea level rise.  You want to wait and see if it really gets as much worse as scientists have projected?  You realize the it will continue to get worse after 2100 in any case?  You want to wait until civilization collapses before you take any action?

    The fact that Arhennius in 1896 made projections that are still in the range of what is expected tells us that scientists are close to the mark.  How long do you need to wait?  It has already been 120 years, why would we need to wait another 30?  James Hansen testified to congfress in 1989, 30 years ago.   Fossil fuel intrests used exactly your argument 30 years ago.  Now that the future has realized we see that Hansens projections were very accurate and you say we need another 50 years to wait?  Does that make sense?

    You are making excuses so that you can make money while everyone younger than you will suffer.  10 years ago scientists did not use the term carastrophic global warming and the deniers (luke warmers do not exist) used that term to insult scientists.  Today scientists warn of catastrophic damages and deniers say it will not be too bad.  The consequences have gotton so much worse in the past ten years that it is no longer extreme for scientists to warn of castrophe.

    Scientists work for 150 years to develop the knowledge to project the future climate.  You do not like the projections because it means you will make less money.  You say we will just have to wait and see if it is really that bad.  There is a consensus that warming over 2C could threaten the collapse of civilization and you say we should wait and see what happens at 4C?  That is insane.

    You produce no peer reviewed papers to support you absurd claims.  You dismiss Stern, Hansen and Jacobson with a handwave.  You have only the opinion of a lawyer who invests heavily in fossil fuels.  You ignore the evidence you are presented.  Why do you waste our time here when you do not care about the evidence?

    Arguing that  you do not understand the consequences of material that you refuse to read is not rational.  

    Please do not insult us here again with your comparisons of "luke warmers" and scientists.

  35. michael sweet @ 1084

    Given the moderator's comments, my plan is to largely sit back and read rather than comment on this website.  In fact in a number of instances I have taken this approach rather than "dive in".

    I actually find this site very valuable and it has clearly focussed my views on climate change perhaps more so than the "other site" that I tend to also read.  I have contributed to this site and plan to do so in the future assuming that I do not get blacklisted.

    But before I sign off for a period of time, I have to respond to what I find troubling about your attitude compared to all of the other regular contributors to this website.

    In many respects, you try to "dehumanize" me.  Like you, I am most interested in the welfare of this world.  No, I am not a selfish capitalist involved in oil and gas matters.  I clearly disclosed my financial interest in the oil and gas business so that everyone could judge my views knowing where I was coming from.  Not everyone on this website has done so.

    But I am 71 years old with my children in no way dependent on the oil and gas industry.  One lives in New York and the other in Vancouver.  Over the next 10-20 years, I highly doubt that that portion of my investments involved in oil and gas interest will be really impacted by this debate.  I am not so stupid as to have most of my "chips" on the oil and gas square. 

    I have zero interest in anything other than what is in the best interests of this world.  And I do mean the whole world and not just Europe and North America.  I am trying to rationalize the massive increases in CO2 emissions and the dangers this creates with still keeping the incredible advances we have made in this world since we leveraged our energy requirements using fossil fuels.  Honest people can have honest disagreements on what to do.

    What I find in your remarks is a reluctance to accept that anyone with a brain could possibly disagree with your views.  Rather than reply to some of my remarks with rational responses you would rather demonize me by suggesting that I have ulterior motives and therefore can be dismissed.  

    But I thought the purpose of this website was to educate.  The moderator has replied to me on my issue regarding the models and I appreciate his information.  I plan to read what he has provided to see if what he has provided to me on the climate models can counter my views.  I thought this was the purpose of this website.  I do not think that every person who provides a comment on this website has to have read every blog on this website before providing a comment.  Certainly by me raising a question about whether we can trust the models to predict temperatures in 50 years this is an opportunity of this website to provide references to evidence to support why we should be able to do so, or reasons why we should do so in spite of the difficulty.

    But you would prefer to attack me as having ulterior motives.  I appreciate that at any time I could be "deleted" from this website, but is that a victory?  I think not.  I think providing information that contradicts my general perception is what rational human beings should do.

     So rather than say that I am a "money grubbing" conservative, I would rather hear from you on my question regarding the models.  The moderator has done so, why not you?

    Response:

    [DB] Off-topic and moderation complaints snipped.

  36. NorrisM @1085 , the primary purpose of SkepticalScience website is educational, through the daily articles and multiple links.   The listed Climate Myths provide a strongly educational underpinning, and indeed there is much to be learnt from the comments columns (where an informal panel of well-educated scientific thinkers provides further explication).

    NorrisM, the SkS website could delete all your comments (and all my  comments, too) and be none the lesser for it.   SkS is far bigger than any individual commenter.   While you and I might aspire to contribute praiseworthy eclat or scintillating enlightenment for the benefit of readers, it is nevertheless true that we have (thus far) fallen completely short of that target.

    Michael Sweet @1084 , your comment is relevant and well-phrased.   If I could expand on it, I would say that the human population [re climate] forms a bimodal distribution.   One peak represents the scientific-thinking people, and the other peak represents the science-denying people.

    Interestingly, there is almost no shoulder region between these two mountain peaks — certainly I myself have never heard of or met someone who truly occupies that "intermediate shoulder" between peaks.

    The mainstream "scientist" group vary only slightly in the degree of expression of alarm about the the speed & consequences of AGW.    ~OTOH the denialist group occupy a wider spectrum, ranging from highly-extreme craziness of denial of reality . . . through to low-extreme craziness of so-called lukewarm positions (positions which still amount to "let's ignore the problem and do little or nothing to tackle it effectively").

  37. Norrism:

    I noticed at the top of this page a reply to one of your posts that is almost a year old.  After a year posting at SkS you still have to be constantly reminded to post on topic.

    I have provided you copius references to peer reviewed papers in that year.  You frequently dismiss these with a wave of your hand.  Recently you stated effectively that nothing James Hansen said was worth discussing. 

    You dismiss the US Climate Change report as not the IPCC and cite a paper that claims minimum sea level rise is much less that the IPCC reports.  Hansen's  paper has 200 citations since 2016 while your citation has only 20 since 2014. That means that scientists think Hansen's paper was important while your paper was not.  You will not listen to what Hansen has to say.  Your position is contrary to science.

    This repeats through the entire year you have posted.  You invariably support "lukewarm" positions at the extreme lowest amount (or below) of possible damage and say all decisions should be based on that possibility.  You do not even consider consensus reports like the US Climate Change report.  You never consider the posibilities of severe effects which scientists fear are possible.  

    That dismissal of severe effects is contrary to all known proper risk management.  If it turns out that the fears of Rignot and Hansen that sea level rises several meters the world will be screwed by 2100.   If it turns out that Curry is correct than sea level rise will be slower and the world will not be screwed untill 2200, but it will still be screwed.  The USA is only 250 years old and sea level rise alone will cause immense damage in less than 250 years.  And you do not care.

    There is no down side to switching to renewable energy.  In 100 years oil will run out and the switch will have to be made anyway.  Why delay the switch untill we have permanently screwed future generations?

    The war in Syria was caused partly by a drought that was the biggest in history (over 2000 years).  AGW predicts drought in that region.  The refugee crisis (millions of people) of the past few years was a direct result of drought predicted in advance as caused by AGW.

    I will not go into more detail about hurricanes destroying cities, wildfires consuming greater and greater parts of the globe, ocean currents slowing, floods, glaciers and ice sheets melting, and other disasters caused by AGW already.  It is too depressing and you do not care.

    You rely on your opinion and refuse to even read articles that describe facts you do not like.  After a year I have lost my patience with you.   As I recall, for the first month or so that you posted I was helpful and tried to give you information.  As it became clear that you did not really want information but just wanted to lecture us on your beliefs (without any evidence to support those beliefs) I have gotten much shorter and shorter with you.  I note that over the past year at least 5 other posters (including the moderator) have lost patience with you and will no longer engage with you.

    This is a scientific board.  You must post data to support your wild claims.  You have consistently refused to support your claims and dismiss data presented to you with a hand wave.  That is the problem.

    Response:

    [DB] The participant to whom you responded has recused themselves from further participation here.

  38. How do you explain the fact that the average of climate models is so far off of what has really happened in the last 30 years?

    https://ktwop.files.wordpress.com/2013/10/73-climate-models_reality.gif

    https://ktwop.files.wordpress.com/2013/10/73-climate-models_reality.gif

    Response:

    [PS] Annual comparisons of models and temperate can be found here. But please look at the post the DK indicates below to understand the misinformation that misled you.

  39. ecgberht, see this post about that dodgy graph: Republican's favorite climate chart has some serious problems.

  40. The most reliable climate model of all is the solar cycle.

    It is 93% accurate when past climate data is used to predict present-day climate.

    https://nextgrandminimum.com/2018/11/22/professor-valentina-zharkova-breaks-her-silence-and-confirms-super-grand-solar-minimum/

    No computer model comes close to that.

    Why do climate scientists refuse to acknowledge the solar cycle as a model for climate change?

    Is it because the solar cydle doesn't yield the desired answer?

    Response:

    [DB] Claims made by skeptic blogs are scarcely credible in this venue.  The gold standard is peer-reviewed papers published in credible science journals and primary providers like NOAA or NASA.  When Zharkova publishes her research in a credible science journal, it will be properly examined.  The blog post you cite contains little actual, verifiable details and is this not credible.

    "Why do climate scientists refuse to acknowledge the solar cycle as a model for climate change?"

    Scientists use a metric called Total Solar Irradiance (TSI) to measure the changes in output of the energy the Earth receives from the Sun. And TSI, as one would expect given the meaning behind its acronym, incorporates the 11-year solar cycle AND solar flares/storms.

    The reality is, over the past 5 decades of significant global warming, the net energy forcing the Earth receives from the Sun had been negative. As in, the Earth should be cooling, not warming, if it was the Sun.

    TvsTSI

    It's not the Sun.

    [PS] See also here on effect of grand maximum. Any further discussion should be on this thread. The solar cycle is not a model. If you want to bet on solar, then consider what happened to last solar physicists who were willing to bet (but have refused to pay up).

  41. JoeTP,

    Your reference only discusses solar cycles, it does not mention climate.  It discusses the magnetic cycles of the sun.  It refers to a presentation made at the GWPF, a well known anti-science organization.  Can you cite a peer reviewed report to support your wild claims?

    Scientists generally have trouble predictinig solar cycles.  Claiming to be able to predict solar cycles hundreds of years in the past and future does not seem like a reasonable claim.

  42. As I've stated in other posts, I am a non-scientist layman. I've gone through thousands of comments on this site and several articles on RealClimate. I just got done reading the article and comments over there on "30 years after Hansen’s testimony" here 

    Based on everything I've read so far, this is what I've internalized (please correct me as needed) — all climate models are obviously dependent upon the assumed inputs of both man-driven forcings and natural forcings, which the models use in physics-based simulations of the resulting outputs. Such models do not pretend to have intradecadal accuracy, rather the target is skill in projecting 30 year trends. Hansen was obviously required to guess those forcings, which he incorporated into 3 different scenarios. His man-driven forcings included not only CO2, but also N2O, CH4 and CFC. His CO2 forcings, in retrospect, were "pretty close" for Scenario B but he overshot on the others because humans actually tackled those other emissions. Gavin at RealClimate took a stab at adjusting Hansen's Scenario B and concluded that the adjusted results indicated a quite skillful model.

    So my (perhaps dumb) question is — why not re-run the actual models with the actual man-made forcings that happened in those 3 decades, to see exactly how close the projections got for Scenario B? It seems like they might be "pretty darn close" and bolster the cause?

  43. AFT - based on a comment izen in this discussion,  I believe this has been attempted but it is anything but straightforward because of changes to compilers, hardware and the state of the data files. There is more about the veracity of the model in this article here and perhaps further comments about Hansen 1988 belong there. In short, the model produces a climate sensitivity that is on the high side compared to modern models for a variety of interesting reasons. However, the article also points out a number of ways in which the model has been misrepresented by deniers. Continued work on reproducing the model is unlikely to help with those who determined to deceive. 

  44. The excellent "Science of Doom" has a critique of your debunk. 

    Someone from SKS may wish to engage.   SoD is generally an excellent site for true scepticism. 

    https://scienceofdoom.com/2019/01/06/opinions-and-perspectives-5-climate-models-and-consensus-myths/

  45. I am not sure his series amounts to a "critique". He states "Climate models are the best tools we have for estimating the future climate state."

    and

    "There are lots of papers written by climate scientists on the difficult subject of evaluating climate models. They do some things well. They do some things badly. Different models get different results. Sometimes widely different results."

    No arguments there.

  46. I have a very simple question. Is it possible to predict what the global climate will look like in 5000 years time using the current models?

  47. Bripuk:

    It is impossible to predict how much CO2 humans will eventually release.   Without that information it is hard to be confident in all future projections.

    If it is assumed that humans stop releasing CO2 in 2050 or 2100 a projection can be made but it will have significant possible unknowns.  Long range projections have been made for 5000 years with a variety of different scenarios.  Some look OK and others are scary.

  48. It's been suggested that 'models are unreliable' is a particularly pernicious myth. The models have been useful, and are getting even better, but some make the false claim that models have deviated demonstrably from reality.

    Those who are misinformed or content to be misinformed often make up unsourced past 'predictions', perhaps because they are reacting against journalists' sometimes sensationalist ways of describing individual studies. Eg in the last few days in response to a climate article: "By 2016, New York will be under a foot of flood-water because of all the melting ice caps, melting glaciers and so on", which is clearly not a direct quotation despite being in quotation marks and impossible to trace as a statement.

    If they're schooled in climate confusion, they might refer to Peter Wadhams's projections of sea ice, or the chat with James Hansen; on social media you often find images of local press cuttings, taken out of context and with pink highlighter taken from Tony Heller's blogs. (There's also the argument, which that because models can't reliably predict short-term weather patterns, how can predictions be made for decades in advance, how the range of weather is affected by changes in the Earth's energy balance.)

    This article includes links to CarbonBrief's series on modelling, but I don't see a link to Zeke Haufather's comparison of historical models against later trends:
    LINK

    (The late Wally Broecker's simple 1975 model was nearly spot on. Then there's the 1979 Charney Report.)

    Also, I found this a useful resource:
    LINK

    It's not just that 'Models successfully reproduce temperatures', but also patterns of warming.

    Putting these together in one image (not sure if it will come out):
    Reliability of climate models from CarbonBrief and Barton Paul Leveson

    Response:

    [PS] Fixed image. Please read comment policy for details of image. You must restrict image to max width of 450px using the "appearance" tab of the image inserter.

    [DB] Shortened URLs

  49. Well, I don't have the credentials of many of you, but I do have some understanding of statistics, modeling, and the like.  I also understand that if you take a graph of temps from any small period of time, (remembering that we could be dealing with a couple of billion years, at least, that you can pretty much get any trend you want, if you only look at a few hundred of those years.  I also often hear thing like 'this is the hottest year since e.g.,1898, which leads me to ask the question about how we have suddenly caused a cataclysm, yet the temps were the same or higher in the 19th century (before the proliferation of the internal combustion engine) Lastly, I know that solar panels generate lots of heat, so why does anyone think that having 100x the number (or more) will somehow reduce the average temperature of 'anywhere'.  Somehow, I think that Mother Nature will take care of the planet just fine, while we waste our time trying to justify a few degrees here and there, when I doubt that we could have done anything to prevent (or help) any of the Ice Ages . . . let's think a little more long term, rather than just a few hundred years . . . then maybe wecan accomplish something productive.

    Response:

    [DB] "yet the temps were the same or higher in the 19th century (before the proliferation of the internal combustion engine)"

    There's no evidence of that.  Please use evidence for claims instead of making things up.

    US Government Hockey Stick

  50. "CommonSense" @1099 :

    <Well, I don't have the credentials of many of you ... >

    Actually, the word you meant was credibility.

    Gain some credibility by citing the evidence that "temps were the same or higher in the 19th century".   Your other claims are similarly bizarre, and seem to be based on religion rather than science.  Or you are simply jesting.

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