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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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Comments 60651 to 60700:

  1. Skeptical Science hacked, private user details publicly posted online
    @yocta The general tone here has been that this was some kind of attack on SkS for ideological reasons and yet it has previously been pointed out that the attack came from Russian hackers who would likely be more motivated by money, ego or status. Your acronym leaves out one letter, "S" for stepping stone. The real value to a group of hackers (having had my site hacked once) is to facilitate further cyber-shenanigans. A list of email addresses allows a hacker to attack those computers, installing bots that allow further attacks on other sites. SkS list has to be a real treat since the base is so large and diverse and so many are associated with educational facilities. At least it hasn't made it to wikileaks yet.
  2. Peter Hadfield Letter to Chris Monckton
    Cornelius, I grew up with hyperthyroidism until surgeons removed most of my thyroid at age 18. I didn't notice that there was anything 'wrong', nor was aware of it apart from my extreme appetite for food and precociousness. I benefited from having a system clock on turbo as a teenager discovering computers! Might explain that I found it difficult to settle and fit in anywhere because I was intellectually unsatisfied by most of my peers and became a maverick, but apart from that I really didn't consider that hyperthyroidism was a big deal.
  3. The Skeptical Science temperature trend calculator
    "the IPCC projection of 0.2°C/decade" Can you give a reference for this? IIRC the IPCC report actually says "*about* 0.2C/decade" - while it may seem like a nitpick, the difference does matter as (for example) 0.17C is by any reasonable interpretation "about 0.2C", but it's not 0.2C. I think this "0.2C' claim actually originates with 'skeptics', and not the IPCC (as by exaggerating the IPCC claim and neglecting the uncertainty, it makes for an easier strawman to attack, at least in the short term).
  4. PMO Pest Control: Scientists
    Rust @24, No surprises there. He and his conservative counterparts are continuing to be disingenuous to this day. This story on the muzzling on canadian federal scientists has just been posted on CBC. The narticle also contains these examples: "A group representing 500 science journalists and communicators across Canada has documented instances where they say federal scientists have been barred from talking about research funded by taxpayers. In addition to DFO scientist Kristi Miller, they cite: An Environment Canada team published a paper on April 5, 2011, in Geophysical Research Letters concluding that a 2 C increase in global temperatures may be unavoidable by 2100. No interviews were granted by Environment Canada's media office. Following the March 2011 Japanese earthquake and nuclear plant problems, Postmedia science reporter Margaret Munro requested data from radiation monitors run by Health Canada. Munro said Health Canada would not allow an interview with an expert responsible for the detectors. An Austrian team released data from the global network of radiation monitors, including stations in Canada. Other examples include: The 2010 case of Scott Dallimore, a Natural Resources Canada scientist who could not talk about research into a flood in northern Canada 13,000 years ago without getting pre-approval from political staff in the office of then-Natural Resources Minister Christian Paradis. Approval came after reporters' deadlines passed, according to Postmedia News. The 2011 case of David Tarasick, an Environment Canada scientist whose research showed an "unprecedented" loss of protective ozone over the Arctic. He was not available to talk with reporters when the research was published, and was interviewed three weeks later. "I’m available when media relations says I’m available," he told Postmedia News." Canadians need to take note of this abuse of science and scientists by the conservative government, it is their reputation and their tax dollars and potentially their safety that are being threatened.
  5. New research from last week 12/2012
    Stefan Rahmstorf has published an article on Realclimate about the paper/article I mentioned @8: Extremely Hot
    Moderator Response: [DB] Fixed link.
  6. HadCRUT3: Cool or Uncool?
    Chris: Yes, the grid cells are weighted by area. An improved method, used by GISS, involves allowing the number of cells to vary by latitude to keep roughly constant area. It's pretty simple in practice. As well as GISS, you might want to take a look at what Nick Stokes has done in TempLS. He's looked at weighting each station by the unique area around it and loads of other nice stuff, some of which anticipated the ideas in BEST. Steve Case: Sorry, I'm talking about anomalies exclusively in the article. I was trying to remember to put the word anomaly in everywhere, despite the repetition, but missed some. Since the temperatures are always converted to anomalies before averaging, the difference in the absolute values disappears. Martin: The land/ocean bias is not enough on its own to explain the difference between HadCRUT3 and, say, GISTEMP. There is another major source of bias in HadCRUT3 as well - you have probably read about it elsewhere. Once we've looked at that I think you will have your answer. I started with the land/ocean bias because it is obvious and introduces the concepts.
  7. HadCRUT3: Cool or Uncool?
    A bias of 0.03°C - that doesn't seem to very much. Is that enough to explain why global warming seems to have stopped?
    Moderator Response:

    [DB] "Is that enough to explain why global warming seems to have stopped?"

    Non sequiter. Please see the following post: http://www.skepticalscience.com/Breaking_News_The_Earth_is_Warming_Still_A_LOT.html

  8. New research from last week 12/2012
    The suggestion that marine species may not be able to migrate quickly enough to keep up with the warming of the ocean is a tad strange. Many marine species are themselves mobile and the sessile members of the marine flora and fauna have pelagic larvae. At every spawning, they are spread far and wide and those that settle in favorable areas grow and prosper. If you have dived on coral reefs around the world you will have seen that the assemblages of animals are virtually identical in all of these. Quite a different situation from the assemblages of animals (pre human) on different continents and islands.
  9. Peter Hadfield Letter to Chris Monckton
    bibasir, Watching a tv wrestler pull a rabbit out of a hat would be an entertaining treat indeed
  10. HadCRUT3: Cool or Uncool?
    Chris G - "I'm thinking that it should be possible to use an alternate method. I have one in mind where each station contributes a measurement that is weighted according to the distance from the station." What you are describing is the GISS method, as described in Hansen and Lebedeff 1987, where the measurement weighting is driven by the observed correlation of temperature anomaly with distance. Each measurement within a certain radius of a point (up to 1200km) is weighted by the distance correlation when calculating an estimate at that location.
  11. HadCRUT3: Cool or Uncool?
    Steve (#8), I think you are taking those numbers from a graph showing monthly averages aggregated over the period from 1901-2000. No way to see if the difference is constant over the entire period, just given those numbers. Your graphs seem to show a divergence becoming more pronounced about 1980, but that is just the old eye-ometer.
  12. The Skeptical Science temperature trend calculator
    Can we have ones for : SLR, Extrem Weather, oil price....:)
  13. HadCRUT3: Cool or Uncool?
    I see "Stephen McIntyre" posts a comment at the Nature site. It's good to be as accurate as possible, but let's not make a mountain out of a molehill; the larger upward trend is not changed much.
  14. New research from last week 12/2012
    shoyemore#14: "the latest offering in the cosmic ray theory of planetary climate," Please don't used the term 'theory' so loosely. As discussed here, cosmic rays may remove ozone. And here, 'ozone hole healing' leads to warming? So more cosmic rays -> less ozone -> cooling. Or more cosmic rays -> more clouds -> cooling. Or whatever you want it to be, using whatever model you want. As long as it doesn't include CO2.
  15. HadCRUT3: Cool or Uncool?
    Dana (#7), I suspect you are talking about the difference between the methods used by US ships versus those used by British ships. http://www.nature.com/news/2008/080528/full/453569a.html Another form of bias introduced, this time by measurement method, rather than calculation method. I wonder how many will cry foul about the changes made at HADCRUT4 without really bothering to check on why the changes were made.
  16. New research from last week 12/2012
    Agreed! RESPECT for the intro!
  17. HadCRUT3: Cool or Uncool?
    From the article: "Until 1980 the bias is small, because the land and ocean temperatures do not differ significantly. After 1980, the difference between the land and ocean temperatures becomes significant ... " Haven't land and ocean temperatures always been significantly different by around 7.5°C? What am I missing? Here's what NOAA says: Land Surface Mean Temp. 1901 to 2000 (°C) 8.5 Sea Surface Mean Temp. 1901 to 2000 (°C) 16.1 Source scroll down half way. Here's a graph I made some time ago that plots out the difference in trend between the two: Here's one I made about the same time that plots just the difference.
  18. HadCRUT3: Cool or Uncool?
    I believe the mid-century 'hump' has been reduced in HadCRUT4, being primarily due to inconsistent sea surface temperature measurement methods at the time, which they have now adjusted for.
  19. HadCRUT3: Cool or Uncool?
    WRT my #4, something is not quite right. I'd expect the WWII temperature hump to be more pronounced in the land than the sea, but that is not the case.
  20. HadCRUT3: Cool or Uncool?
    I need to move on to other things, but it seems to me that deciding on a grid model, any grid model, presents its own challenges and shortcomings. I'm thinking that it should be possible to use an alternate method. I have one in mind where each station contributes a measurement that is weighted according to the distance from the station. Not sure how to explain the math, but I visualise it as a globe with a calculated height above it (false surface map/tent) where the height above the 'sphere' represents the temperature (or temperature anomaly). How much any station contributes its measurement to the temperature value any given point on the surface is a function of how close it is to that point, and how much other stations are also contributing their measurements to that point. Total weights for all stations at any give point is always scaled to 1. Once you have the contour of the surface defined, you can integrate over it any way you like, grid it out, whatever. Sounds complicated, but it would not be that difficult to program.
  21. HadCRUT3: Cool or Uncool?
    Hmm, that spike in land percentage around WWII happens to coincide with the hump in the temperature record. I suspect the hump is a little exaggerated. Relative to GISTEMP, it is. Thanks Kevin, Now I'm thinking about the 5 degree grid. When it comes to the global averaging, and 5 degree cells are not all the some size, the math to weigh a fixed surface area size equally becomes complicated. IMO, you'd have to weigh surface area equally if you are talking about a global surface temperature average.
  22. HadCRUT3: Cool or Uncool?
    Chris: Yes, you are right about circulation being a critical factor in the slow warming of the oceans; i.e. you have to heat a lot more water because it keeps changing over. HadCRUT3 uses a fixed 5 degree grid. That also means that the high latitude cells are smaller than the equatorial cells, so you actually need a higher density of stations at high latitudes to achieve the same coverage. The common anomaly method used in CRUTEM3 also means that they lose stations as they go away from the baseline period (1961-1990).
  23. HadCRUT3: Cool or Uncool?
    Nice job explaining the problem of making sure that a sample represents the population. Pretty simple coverage here, for sure, but there are entire courses on avoiding sampling bias. "How do you know your random sample is really random?" and so forth; so, good for this venue. Question regarding: "...as would be expected given the higher heat capacity of water." I'm thinking that the temperature difference would have more to do with the fact that water tends to circulate to depth more than land does; so, you get the same energy distributed over more mass. On land, there is less "buffering" because the surface warms, and it takes a long time for the energy to equilibrate to much depth. Water cp ~= 4.2 (J/(g·K) Silicate rock ~= 0.75 (J/(g·K) but rock is about 3 times more dense; so, the difference per volume is about 2x. So, yeah, a given volume of water has about twice the heat capacity. But, I'm still thinking it has more to do with circulation because if you put rocks in a bucket of water, they all come to the same temperature in not much time. "Land coverage in the HadCRUT3v record has been declining over the past 50 years." Really? I could see them making use of a different set of stations, for various reasons, but I would expect them to grid it out so that the actual land surface area coverage did not decrease. Oh, I think I get it. They like to pretend that areas with poor coverage do not exist (at least for the calculations) and the sea surface coverage has been increasing relative to land surface. Ah, alarm bells just went off on my sampling bias detector. Double counting the coastal cells does not really improve the situation either. Nice bit of showing that stratified populations need to be sampled independently, their means calculated independently, and then trend and other analysis performed.
  24. Dikran Marsupial at 02:55 AM on 28 March 2012
    The Skeptical Science temperature trend calculator
    Barry, following on from what Daniel says, the "normal circumstances" for statistical significance tests include the period you are looking at being randomly chosen. In this case the period is not randomly chosen, the question that Phil Jones was asked was loaded by having a cherry picked start/end date, which biases the test towards the desired result. "Warmists" could similarly bias the test by starting the period in say 2000, and the fact that they don't (other than to show why cherry picking is a bad thing) shows who is seeking the truth and who isn't! ;o) IIRC Phil Jones actually gave a very straight answer to the question (no it isn't significant, but it is very close to being significant and that you need more data to be able to expect to reach significance). I suspect that much of the misunderstanding is due to some sceptics having only a rather limited understanding of what significance tests actually mean. Unfortunately they are not straightforward and are widely misunderstood in the science, and even amongst statisticians! ISTR reading a paper where the authors had performed a survey of statistics students understanding of the p-value, and compared that with the answers given by their professors. A substantial majority of the professors failed to get all five/six questions right (I would have got one of them wrong as well). So if you struggle with statistical significance, take heart from the fact that we all do, including statisticians! ;o)
  25. New research from last week 12/2012
    Ari: I love your intro!
  26. New research from last week 12/2012
    @Kevin C #18: Dumb questions: What the heck is the half-life of a scientific journal? How is it determined? By whom?
  27. HadCRUT3: Cool or Uncool?
    Once again, a great job of explaining for the scientifically challenged.
  28. New research from last week 12/2012
    ISI Web of Knowledge give the following for Journal of Atmospheric and Solar-Terrestrial Physics: Cites: 4788 Impact: 1.579 5 year impact: 1.610 Immediacty: 0.298 Articles: 298 Half life: 8.7 I don't know much about the numbers, and I understand they vary by field. 'Environment Research Letters' has an impact of ~3, but a half life of only 2.4 years. 'Solar Physics' has an impact of ~3.3, and a half life > 10 years.
  29. New research from last week 12/2012
    Ari, it is straightforward for the hockey schtick blogger. Lindzen says that cloud cover makes things cooler and this is what happened in (parts of) Europe. Therefore, Lindzen's low climate sensitivty estimates are truthy. Past time I hunted down some more papers for your site. :-)
  30. New research from last week 12/2012
    Sorry, clicked "submit" by mistake. This series is a great way to keep up with upcoming research. Thanks, Ari!
  31. New research from last week 12/2012
    Can species spread fast enough to keep up with climate change? It's not the first time I see a paper showing problems with species having trouble shifting poleward fast enough. Some guys try to argue that species can adapt to AGW. Come on! it's too fast for a lot of species to move fast enough, let alone evolve to adapt! This "new research" series is a great way to keep up
  32. Daniel Bailey at 01:14 AM on 28 March 2012
    The Skeptical Science temperature trend calculator
    Barry, my takeaway from Santer is that a 17-year minimum length of time series is the minimum under "normal" circumstances. As Tamino and others have shown, under optimal conditions, a shorter time series may return a series surviving significance testing, but only after rigorously controlling for exogenous factors to minimize spurious noise. HTH.
  33. The Skeptical Science temperature trend calculator
    Kevin - thanks for a straight answer. It seems I can make use of the tool in a limited way after all. I'll keep plodding. It seems that one were best to avoid making bold statements on trends that border on being statistically/not statistically significant. A bit more data, a few more months in this case, can undo your assertion. I liked Robert Grumbine's Jan 2009 post (one of a series) on minimum periods to usefully determine global temp trends (20 - 30 years). Santer et al (17 year minimum) and Tamino (and I think Rahmstorf in a 2007/8 paper on the most recent 17-year temp trend) have indicated that less than a couple of decades is sufficient to get a statistically significant trend, but it appears that these are unfortunate suggestions to have advanced in the popular debate. At 17 years to present, NOAA, HadCRUt, RSS and UAH all fail statistical significance (using the SkS tool - I think!). A theme that keeps popping up for me as a reader is the problem of balancing completeness with making things accessible to a lay audience. The 17-year thing (which is now cited in the skeptiverse), and Jones' latter comment on statistical significance in the HadCRUt record being achieved, which was made into a post here, are good examples. It seems to me that the message can be pushed harder than the facts when they are oversimplifed. Bookmarked this page and look forward to making use of the great new gadget. Thanks be to the creators.
  34. Cornelius Breadbasket at 00:35 AM on 28 March 2012
    Peter Hadfield Letter to Chris Monckton
    I have followed Monckton's progress from the time that he was the designer of a mathematical puzzle in the 1980s (the Eternity Puzzle). Before then he was a ‘parliament botherer’. Very good friends of mine was a civil servant in the Thatcher government and has related how Monckton would turn up unannounced, and assume a position of authority within a department when no authority was given. Monckton is superb with words – an excellent speaker with a formidable lexicon. He has a phenomenal grasp of both mathematics and human nature. He is a showman – a master of reading the subtle signals in a crowd so that he can give them what they want to hear. In this way, Monckton appeals very much to an older generation, those who do not want to believe that the climate has been changed by human activity. He gives them relief from guilt and permission to continue their lives without what they may perceive to be a threat to their hard-earned lifestyles. However, Monckton is quite obviously not a figure to be ridiculed and ignored. He has presented to (and misled) the US Congress on (two?) occasions. He is deputy leader of UKIP, a political party here that aims to separate the UK from the EU. He is a popular speaker all over the world with a dangerous message. He is – as one commentator has suggested – the epitome of a demagogue. There is always one thing that is overlooked about Monckton that fascinates me. His illness. A friend of mine is a doctor who watched a video of Monckton with me. She guessed without knowing that he suffered from Graves disease, both because of his eyes and his personality. This seems to be considered unworthy to mention. I can understand that we should be fair to him because he is not guilty of causing his hyperthyroidism – and because it is a horrible complaint that he obvious bears with fortitude. However, I can’t see why, when the stakes are so high, that we have to ignore that thyroid disorders are usually accompanied by mental illness and symptoms such as Histrionic Personality Disorder which results in the need to be the centre of attention . At the risk of invoking Godwin’s law – Hitler suffered brain damage from gassing in the trenches during the First World War. I wonder if he would have been quite so popular if more people had known. I wonder how history will judge us for sweeping Monckton’s illness under the carpet.
  35. New research from last week 12/2012
    The Kilifarska paper that stratospheric ozone is the most important driver of planetary climate seems bizarre. It is the latest offering in the cosmic ray theory of planetary climate, and is already hailed on one denialist blog, especially as it predicts imminent cooling. I notice that Tamino at Open Mind has scant respect for the Journal of Atmospheric and Solar-Terrestrial Physics, which he describes as "sinking further and further into disrepute", though he is discussing a different paper. http://tamino.wordpress.com/2012/03/22/mathturbation-king/
  36. Dikran Marsupial at 23:46 PM on 27 March 2012
    New research from last week 12/2012
    @martin, that journal has also published a couple of rather questionable papers by Scafetta. I suspect they need to attract more reviewers with a solid grounding in climatology and/or statistics. It is possible that they have a good reputation in other areas of solar physics, but it seems to me that they have a bit of a problem when it comes to climate related work. As a statistician, I am rather sceptical about concluding that 75% of temperature variations being due to a factor that had previously not been thought of as of great importance, based on a statistical model, especially a non-linear one. However I haven't read the paper, so I can't comment further, other than to say that extraordinary claims require extraordinary evidence.
  37. New research from last week 12/2012
    Biosphere responses to climate change is such a complex field. Everything is so interrelated in ways we do not always understand. The Hiddink et al paper is in their words an optimistic analysis, and yet it is still very worrying. There will be unexpected surprises. You would expect that seals that occupy a similar niche would all be affected the same. But the Weddell Seal may end up worse off the quickest, because Orcas have a strong preference for Weddell's. Robert Pittman and John Durban (NOAA) have documented some interesting behavior.
  38. New research from last week 12/2012
    Re - Climate Sensitivity and Ozone Does anybody know anything regarding the reputation of the Journal of Atmospheric and Solar-Terrestrial Physics? That paper also mentions galactic rays and that makes me quite skeptical.
  39. New research from last week 12/2012
    CBDunkerson you should value yourself more, just add facts and logic and stuff and publish your ideas. :)
  40. New research from last week 12/2012
    Hmmmmmm... Trenberth 2012: "The answer to the oft-asked question of whether an event is caused by climate change is that it is the wrong question." Dunkerson 2011: "The whole question 'what caused weather event XYZ' is inherently flawed." Trenberth 2012: "All weather events are affected by climate change because the environment in which they occur is warmer and moister than it used to be." Dunkerson 2011: "Thus, it could be reasonably said that ALL weather we see now is due to global warming. It is all an aspect of the current climate, which has been changed by AGW." Ok, that's it Trenberth! I'm calling you out for putting my crazy blog comment ideas into a peer reviewed scientific paper, and backed up with facts and logic and stuff! How could you do that to me? How am I supposed to maintain a reputation if you go around making my inane ramblings seem valid?! Tis a sad day. :[
  41. New research from last week 12/2012
    Just spotted this by Rahmstorf and Coumou: http://www.pik-potsdam.de/news/press-releases/wetterrekorde-als-folge-des-klimawandels-ein-spiel-mit-gezinkten-wurfeln The past decade has been one of unprecedented weather extremes. Scientists of the Potsdam Institute for Climate Impact Research (PIK) in Germany argue that the high incidence of extremes is not merely accidental. From the many single events a pattern emerges. At least for extreme rainfall and heat waves the link with human-caused global warming is clear, the scientists show in a new analysis of scientific evidence in the journal Nature Climate Change. Less clear is the link between warming and storms, despite the observed increase in the intensity of hurricanes.
  42. The Skeptical Science temperature trend calculator
    Oh yes, Nick's explanation (Jones was using AR(1)) seems more plausible than Lucia's (Jones was using annual averages), given the wide use of AR(1) in the field.
  43. Dikran Marsupial at 21:43 PM on 27 March 2012
    The Skeptical Science temperature trend calculator
    @barry, essentially if you can draw an horizontal line within the "error bars" covering the whole period of the trend, then it isn't statistically significant (as a flat trend is consistent with the data). Regarding Phil Jones' comment, the trend under discussion was hovering about the boundary between "significant" and "not significant", so small changes in the way the calculation is performed is likely to change the result. I want to congratulate Kevin C on an excellent job, the trend calculator gives a very good indication of the uncertainties, and is definitely more accessible to a non-statistical audience than explaining what statistical significance actually means (and more importantly, what it doesn't mean).
  44. The Skeptical Science temperature trend calculator
    I did a study of Phil Jones observation here (near the end). I think he's right. Significance goes down as you take account of autocorrelation. I found that if you don't allow for it, the trend of Hadcrut3 since 1995 is highly significant (t-stat of 5). But if you allow for AR(1) dependence, it comes down to 2.1, just marginally significant. As noted in Foster and Rahmstorf, AR(1) isn't quite good enough. I tried AR(2), which brought it down to just below significance. But most people think AR(1) is reasonable, and I think that's probably what he used. And I think that measure did cross the line somewhere during 2010/11.
  45. The Skeptical Science temperature trend calculator
    Barry: I agree, the uncertainties calculated by this method do not support Phil Jones' claim that HadCRUT3v snuck into statistical significance from 1995 part way through 2011. If I remember correctly, Lucia performed a very critical analysis of Jones' claim over at the blackboard. I think she deduced that his claim was based on calculating annual means, and then calculating the simple OLS trend and uncertainty on the annual means. That is a rather more crude way of dealing with autocorrelation, and while much better than using OLS on the monthly data, it still tends to underestimate the uncertainty a bit. Therefore, to my best understanding Jones' claim was wrong. (Caveats: estimating the autocorrelation is also noisy, and Tamino's method may not be optimal. I'm interested to see where Nick Stokes goes with this - he is certainly in Tamino's league when it comes to statistics.) As to what is going on with HadCRUT3 - there will be another post along shortly!
  46. Peter Hadfield Letter to Chris Monckton
    Long time lurker; first time poster. jimb, you wrote: "I have been wondering if Monckton, when he gets back to his hotel room after the applause has died down, feels even slightly embarrassed by the quality of the audience he attracts." I don't think he is at all embarrassed. I think he is a classic narcissist who (a) believes all he writes, (b) loves and needs the adulation, (c) realizes he is onto a very good thing: someone who will pay his way, audiences who love him because he supports the status quo they want, a network of deniers who support him and to whom he in turn can offer support. If he ever doubted that what he writes is nonsense, that cognitive dissonance is easily overcome by all the support he gets from adoring audiences--"they love me so I must be right!" His debate with Peter Hadfield is done and Anthony Watts has cemented that. He will just steer clear of any real debate; Tim Lambert got to him on stage, but he's the only one, AFAIK. I get a kick out of some of his nonsense: you've just gotta laugh at his pompous claim that he and others are trying to get U of C. shut down, but his audience would love (and obvious did love) him making such a threat. The only thing that could deflate his circus tent is if he libels someone with one of his outrageous ad homs and someone takes legal action.
  47. The Skeptical Science temperature trend calculator
    Barry @11, the null hypothesis is not that there is no trend. Actually, I don't like the term "null hypothesis" because it is as misunderstood and abused as the term "falsification", and generally when it pops up in argument, the "null hypothesis" always turns out to be the hypothesis that the person arguing wants to be true. In general, it is far better, and far more transparent to be good Popperian's and simply state whether or not the test results may falsify the hypothesis being tested. ("May" because approx 1 in 20 tests will fail the test of statistical significance even if the hypothesis is true. Seizing on just one example of this and saying, "look the theory has been falsified" simply demonstrates that you do not understand falsification.) Whatever the time frame, the trend is statistically significant if its two sigma (95%) confidence interval does not include a given test condition. So, if we want to say that the trend is positive, that passes the test of statistical significance if and only if no trend line within the two sigma confidence interval is negative. If we want to claim the medium term temperature trend of approximately 0.17 oC/decade has ended, that claim is statistically significant if and only if the trend of 0.17 oC/decade does not lie within the two sigma confidence interval. If we want to say the purported IPCC predicted trend of 0.2 oC/decade has been falsified, that claim is statistically significant if and only if the trend of 0.2 oC/decade lies outside the two sigma confidence interval. The two sigma confidence interval for the trend from 1995 to 2012 using the HadCRUT3 data is -0.048 to 0.21 oC/decade. Therefore, the claim that the temperature trend over that interval is not flat, the claim that it has changed from the ongoing trend, and the claim that it has falsified the IPCC predicted trend are all not statistically significant. Fake "skeptics" often want to treat the truth of the first of these claims as a proof that the other two are false. At the best, they are trying to draw attention to that fact while scrupulously not explaining that it is in no way evidence that the other two claims are false (which is disingenuous). As it stands, the lack of statistically significant warming from 1995 to 2012 as measured by HadCRUT3 is no more evidence that the long term trend has ended than was the lack of statistically significant warming from 1981-1998 on the same measure. And of course, Foster and Rahmstorf show quite conclusively that the underlying trend does in fact continue.
  48. New research from last week 12/2012
    jyyh, skywatcher I picked up a 1.2m satellite dish 15 years ago and covered the matt white surface with aluminium foil. The LNB holder was an aluminium ring supported by 4 struts coming out of the face of the dish, and the dish had a small hole at the centre that could be used to accurately align with the sun through the LNB ring. The power of this thing was awesome. Holding a large log at the focus just caused it to spontaneously char in under a second and fill the garden with smoke - lots of it. (I resisted the temptation to test with my hand!) I couldn't measure the temperature, but estimated about 1kW/cm² density - Wolfram Alpha wasn't much help in converting this to °C. Having set it up, I coated the bottom of a pan with soot from a candle, held it at the focus for about 1-2 minutes and made a cup of tea with it... My first home-made fusion-powered cup of tea, and it tasted wonderful! :-) There must be millions of discarded satellite dishes around the world just waiting to be converted and shipped off to Africa to help reduce deforestation. I have some ideas for improving its efficiency in focussing and capture... something for a rainy^H^H^H^H^H sunny day. Alas I don't have the dish any more, ex-wife threw it out :(
  49. The Skeptical Science temperature trend calculator
    Thanks, Tom. I know you meant to say Phil Jones. :-) Still don't know if or how I can use the SkS temp trend calculator to determine if a trend is statistically significant or not. Your reply only confused me more. I didn't mean to make hay out of the Jones/1995 thing, but while we're here... Laypeople like myself rely primarily on a coherent narrative. The skeptical camp don't offer a whole bunch of that, so it is particularly striking when mainstream commentary seems to deviate. Prima facie evidence is that 17 years is a good minimum time period to establish a robust climatc trend. (If that is too simple-minded, then mainstream commenters may have contributed to that understanding by heralding the result as a way of dismissing the memes about shorter-term trends) Being a failry avid follower of the debate, I've long been aware of the lack of polar coverage in the HadCRUt set (currently being replaced with version 4), the perils of cherry-picking, and the noisier satellite data. IIRC, Santer determined the 17 year minimum using the noisier TLT satellite data, so your concern about avoiding RSS and UAH may not apply? On the one hand I've got the 17-year minimum for statistical significance that should apply comfortably to surface temperature data, and on the other an uncertainty interval that is larger than the trend estimate, suggesting (to my stats-starved brain) the null hypothesis (of a flat trend) is not rejected for the HadCRUt3 data. This has implications for the Phil Jones/1995 trend narrative as exposited by the mainstream camp. If I have to refer to a longer-term trend to get the picture, as you say, how do I now read the recommendation of Santer et al that 17 years is a standard minimum to get a robust climatic trend? Somewhere along the road here I have failed to learn (most likely), or the description on how to read the significance values is not quite clear enough in the top post. In any event, I'm all eyes for a better education.
  50. Ari Jokimäki at 17:57 PM on 27 March 2012
    New research from last week 12/2012
    Well, that's just wrong. Decreasing cloud cover is (generally) a positive feedback to warming. If it would support Lindzen's hypothesis (assuming it's the Iris hypothesis we are talking about), then the cloud cover would increase during warming and therefore resisting the warming. Here of course the situation is a bit complicated as there is an area of decreasing cloud cover and an area of increasing cloud cover. However, we see that in areas of warming, cloud cover has decreased (which causes warming effect) and in areas of cooling cloud cover has increased (which causes cooling effect). Now, if we extrapolate this situation to global context (which is not necessarily a good idea) where the whole globe is on average a warming area, then we see that globally this would mean that cloud cover is decreasing which would cause a positive feedback to global warming. Observations of global cloud cover, by the way, show either constant or decreasing global cloud cover (edited to add: in the long term, that is).

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