>> You know it's posts like this that give climate science a VERY bad reputation. I've got a degree in statistics, so I read your post and immediately 3 alarm b

>> You know it's posts like this that give climate science a VERY bad reputation. I've got a degree in statistics, so I read your post and immediately 3 alarm bells go off. You've got a degree in statistics, and I have a PhD "in" Oceanography, does it make a difference? Not really. >> It is WIDELY known in scientific circles that IPCC predictions have a bit of a nasty habit of having, firstly, very dubious statistical underpinnings (which is another way of saying their methodology is complete shite). Secondly, without making any political claims, they systematically overstate the problem by a LOT. The IPCC produce assessments of published research, but do not, as a body, perform research, or make predictions. Their methodology is to assess existing research, and to attempt to construct a representative summary. This is pretty much the only way one can conduct a literature review, so it is difficult to see why you would describe it as "complete shite". >> And yet here you are, making the exact opposite claim. But there are a few alarm bells. You strongly disagree with how I thought I know the world to be, and you make an oddly specific cherry-picked argument. Here's what I mean: I haven't made any claims, or disagreed with anything, I simply referred you to published literature on the subject which you mentioned. >> 1) broad claim that would barely gain support from the rest of your argument I don't understand what this means - I was only trying to provide you with some of the observational evidence relating to your claim. >> 2) weird pick of the predicted variable (obviously the main predicted climate variable is "temperature anomaly") so why don't you go for that one ? (Ie. is this a case of "we got the basics of our prediction wildly wrong, but in this long list of things we touched on sideways we lucked out majorly and see ! We were right after all !" ?) I "picked" the variable you were talking about: sea level rise ("So given that the worst IPCC predictions only predict about a 2m water level rise, and that so far the first 20 years of those predictions turned out to have been WAY overblown, I think we'll do just fine as a species, even long term." for reference). >> 3) You pick the "third assessment report" (which is actually the fourth, because counted from 0). Pray tell, how did predictions 0, 1, and 2 go ? Your claim (which I read as being that the first 20 years of sea level rise predictions were "WAY overblown") is incorrect (putting philosophical points about the nature of truth to one side). I know it is incorrect, because I have read so many papers, and been to so many talks, that describe evidence to the contrary. I typed "sea level rise predictions" into google, because I know that skepticalscience have good articles that explain the various issues, and I found the one that I wanted. I can go and find more, if you really need it. >> 4) You picked the third assessment report. Hmmmm. Was this even a prediction ? The comparison stops in 2002 on your linked graph. When was AR3 released ? See above. But: it is the tide gauge data (in red) that stops in 2002, not the predictions. The comparison I referred to was with the satellite data (in blue), which continues to 2009. If you can't be bothered to find out what happened to the tide gauge data then let me know, and I'll look into it for you, for both our sakes. I can, however, be fairly confident in suggesting that it's probably not a grand conspiracy. >> Let's take the easiest one of these questions and check it out. The fourth one: >> https://en.wikipedia.org/wiki/Intergovernmental_Panel_on_Cli.. https://en.wikipedia.org/wiki/Intergovernmental_Panel_on_Cli.... >> Okay so the prediction of the IPCC from 1970 to 2002/2006 (different datasets) has a publication date of 2001. Whereas from all the IPCC predictions there are plenty available to do better checks of their accuracy. Very, very suspicious. So really, there's only a single datapoint in there (for both series) that is actually a prediction (ie. not known at the time of publication, and only 1/7th of any of the data is predicted. Furthermore, the graph neglects to point out where this prediction actually started, which probably led you to make the wrong conclusion) I can't understand what you're trying to say here. What does "different datasets" refer to? What is the "single datapoint"? The prediction on the graph I linked to is the gray band - it is fairly clearly marked, and I would recommend reading the article to understand the context. You seem to have misunderstood what was prediction and what was observation. I haven't made any conclusions, only referred you (both indirectly and directly) to the conclusions of experts in that sub-field. >> Now let's look at alarm signals 2 and 3 and let's actually evaluate IPCC accuracy. Blogposts made by others you probably found by Googling your wanted conclusion are apparently allowed in support of one's argument, so: https://judithcurry.com/2015/12/17/climate-models-versus-cli.. https://judithcurry.com/2015/12/17/climate-models-versus-cli.... >> Oops ... You do understand, right, that the graph I showed you demonstrates that the models are underestimating sea level rise? In other words, it is showing that the models used to compile that figure, which were state of the art at the time, were relatively poor (though not terrible) predictors of sea level rise - something we can probably agree on! >> "Based upon these and other lines of evidence (laid out in our numerous scientific publications, books, blogs articles, social media (see publications listed here and here for example)), we conclude that future global warming will occur at a pace substantially lower than that upon which US federal and international actions to restrict greenhouse gas emissions are founded." You can claim that the page I linked to and the page you linked to are comparable if you wish. One reports the synthesis of the efforts of thousands of scientists around the world who are ostensibly apolitical, the other the work of a group of people who have an explicit political agenda. You can draw your own conclusions about their respective credibility. >> So in conclusion, your main claim, that the IPCC reports contain accurate predictions, aside from being overly broad, is weakened by your listed sources. It is also widely known to be wrong, and indeed on closer observation it is wrong. You seem to have misunderstood the figure - I described how above. The only sources I listed were those for the figure. >> (I have in fact ran the numbers myself, IPCC methodology is crap, and it has in fact had predictable results : disastrously wrong predictions. The IPCC would have to be correct for tens of thousands of years from this point forward to make their "95%" predictions actually correct in 95% of cases) What numbers have you run yourself? Your second sentence must be misphrased, or I am simply incapable of understanding it - it appears to fundamentally misunderstand the meaning of a predictive distribution. >> Another "non-political" interesting factoid: the IPCC has stopped giving values for the climate forcing variable in their latest report. I would just like to point out that this is not the correct way to inspire confidence in one's predictions. You should review Chapter 8 of "The Physical Science Basis", titled "Anthropogenic and Natural Radiative Forcing". Find it here: http://www.ipcc.ch/report/ar5/wg1/ http://www.ipcc.ch/report/ar5/wg1/ >> And of course, there are people, even in my own university that won't just make claims like yours, outrageous and wrong, but actually use the administration to suppress people correcting them. A decent portion of the statistics/math and some in the physics department have suddenly found themselves defending basic math. Whilst none of this of course reflects directly on the science behind it I would just like to make a final point that climate science was recently (few years ago actually, I'm getting old) relocated in my university. It used to be part of the science department. It is now part of the humanities. You know, where theology and philosophy goes. Which university is that? >> Do you wish to retract your statement ? See above.