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Bob Lacatena at 01:10 AM on 16 June 2011The greenhouse effect is real: here's why
29, Tom Curtis, Yes. I agree with all of your points... but still, to me, the issue comes back to one of precise quantification. The logic is there, but (as we've seen is already the case with the simple task of measuring and computing what are obviously rising global temperatures) getting through the noise to an indisputable argument is tricky. -
Dikran Marsupial at 01:04 AM on 16 June 2011Phil Jones - Warming Since 1995 is now Statistically Significant
KR yes, that interpretation is fine, but it still admits that it is not significant (so they would probably make the same claim anyway - logical consistency had nothing to do with it!). The real problem is then when a skeptic has a non-significant statistic, are they allowed to say that the statistic is suggestive of support for their theory? The reason we are not supposed to claim anything based on a statistically insignificant statistics is to guard against confirmation bias. Essentially we should always apply the intepretation that provides the weakest support for our own position. Jones did just that, the Daily Mail did the exact opposite and used the (incorrect) interpretation that provided the most support for their position. However in reality hypothesis tests generally provide little support for any position (and so a pessimistic intepretation is a good idea). I don't mean to be argumentative, it is just that Jones did a very good job of dealing with this very difficult question. I don't think I could have done any better without the use of diagrams and a page or two of text. -
macoles at 00:56 AM on 16 June 2011Phil Jones - Warming Since 1995 is now Statistically Significant
MoreCarbonOK Pardon my earlier assumption that your wild variation of month based trends was due to your treatment. I was able to replicate a very similar trend of -0.108 C/yr for the Brisbane AP May Minima series. Although it is also apparent that the detrended standard deviation is 1.18 C (or 33% of the total trend change over the period). However the fact remains that, just as no-one would base average global temperatures on just 10 sites to show a statistically significant warming trend, no-one would seriously base a SH cooling trend on just 5 sites. You need far more site dirversity before you can make the point that you do. -
John Russell at 00:55 AM on 16 June 2011Phil Jones - Warming Since 1995 is now Statistically Significant
Dikran writes: "Media training is vital for any scientist that need to have contact with the press, but nothing can provide a 100% bulletproof defense." Well then, I think we agree; because I was never saying there is a bullet proof way to respond. Rather I was saying that, in his innocence, Phil Jones made it much too easy and there would have been ways of expressing an honest answer that would have been more difficult to twist -- or even if twisted, easier to demonstrate as obfuscation. I'm sorry I can't come up with one, but that's because I'm not an expert on the science. Cheers! -
Tom Curtis at 00:49 AM on 16 June 2011The greenhouse effect is real: here's why
Sphaerica @28 considering just the radiation, a reduction in aerosols will result in a cooling stratosphere and warming troposphere. That may (or may not) be countered (or reinforced) by chemical interactions between sulfates and ozone. I will point out three things with regard to your point @20: First, the H2O feedback effects which cause even solar warming to partially mimic the CO2 feedback are acting against the natural signatures of solar forcings, but reinforcing the natural signature of the greenhouse effect. Therefore the signature will be stronger for a greenhouse forcing than for a solar forcing. Second, the feedback effects will only significantly mimic the greenhouse signature overall if the H2O feedback is a strong feedback. If it is weak it will not swamp the opposite sign signatures from a solar forcing so that solar forcings mimic greenhouse forcings in both sign and (approximately) magnitude. Third, the H2O feedback will not mimic the stratospheric cooling because the H2O is not carried to the stratosphere because of the very low temperatures at the tropopause. The effect of these three points is that any honest analysis of the greenhouse signatures will place an honest skeptic in the position where they must either accept a GHG driven global warming because of the signatures, or accept it because they are committed to a strong feedback along with the cooling stratosphere. -
Albatross at 00:46 AM on 16 June 2011Phil Jones - Warming Since 1995 is now Statistically Significant
JMurphy @108, The Moniker was a clear give away. IMHO, his posts belong on the "denial" thread more than they do here. And the irony, a post about cherry picking and the guilty party who thinks that doubling or trebling CO2 is OK goes right ahead an cherry picks to continue to reinforce their opinion on the matter. Meanwhile for the period which we almost have (almost complete global coverage) sufficient data to determine statistically significant temperature trends we get this:
[Source]
The planet is in a net energy imbalance and is warming....deal with it folks.
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KR at 00:42 AM on 16 June 2011Phil Jones - Warming Since 1995 is now Statistically Significant
Dikran - So, incorrect terminology and implications (thanks, I don't have multiple publications in statistics): Would this be more correct? "Statistical significance at the 95% level means that there is a 1 in 20 chance of seeing a trend as large or larger assuming the null hypotheis is true, while statistical significance at the 93% level means that there is a 1 in 14 chance of seeing a trend as large or larger assuming the null hypotheis is true. So again, while 93% significance over that period is suggestive, the short time frame data does not meet the statistical significance threshold, which is why 20-30 years of data is preferred to clearly identify trends." The major point aimed for here is to emphasize that while the data is pointing in a particular direction, it's not doing so strongly enough to meet the standard test - hopefully not leaving room for the interviewer (or onlookers) to say "No warming since 1995"... -
Eric the Red at 00:38 AM on 16 June 2011Forecast: Permanently Hotter Summers in 20-60 years
If you are unwilling to listen to his presentation, then fine. That is your loss. Also, if you are so willing to dismiss every other climate forcing and cling to the "its only CO2" argument that influences the climate, then why do you even bother posting? Since his presentation is a direct challenge to the above statement that "simulations have accurately predicted the Earth climate during the past 50 years," which is so blatantly false, I would consider it quite relevant. Not to mention the questionable statement that, "the tropical regions may see the most dramatic changes first." In the U.S., summers may be hotter than the most recent 50, but will they be hotter than the hottest summers of 75 years ago?Response:[DB] Please see http://www.skepticalscience.com/1934-hottest-year-on-record.htm. Also, please try to keep the tone more civil. As others have pointed out, Latif himself is on record as saying he was misrepresented. But that entire episode is off-topic here. If you wish to pursue it, then do so at the link Sphaerica provided.
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Dikran Marsupial at 00:38 AM on 16 June 2011Phil Jones - Warming Since 1995 is now Statistically Significant
Tom Curtis wrote "Where I do part ways with you, and agree with John Russell is that because it is always possible to answer better, I think media training would be useful for climate scientists who are often called upon to front the media. " Actually, I don't disagree with that at all, in fact I said media training is vital for any scientist that needs to communicate with the media. It is the particular question that is the problem, I doubt there is an accessible answer that can't be substantially misconstrued. I think Jones' answer was better than any of the alternatives presented so far. The was a logical disconnect between the "the trend is not statistically significant" and "there has been no warming". If your opponent is not required to be logically correct, there is little you can do, especially with a topic as counter-intutive as hypothesis testing. There are plenty of working scientists who don't understand it properly. -
Dikran Marsupial at 00:31 AM on 16 June 2011Phil Jones - Warming Since 1995 is now Statistically Significant
KR sadly that interpretation isn't correct. Statistical significance at the 95% level means that there is a 1 in 20 chance of seeing a trend as large or larger assuming the null hypotheis is true. That does not mean that there is a 1 in 20 chance that the null hypothesis actually is true. This is mixing frameworks, but the p-value is p(x>X|H0), where x is the trend and X is the observed trend and H0 is the event that the null hypothesis being correct, however what you actually want is p(H0|x>X), which you can get by Bayes formula p(H0|x>X) = p(x>X|H0)p(H0)/(p(x>X|H0)p(H0) + p(x>X|H1)p(H1)) however the hypothesis test does not involve p(H0), p(H1) (the prior probability that the null and alternative hypotheses are correct) and p(x>X|H1), which measures how likely such an extreme statistic is assuming that there is a secular trend. Essentially a frequentist hypothesis test does not allow you to assign a numeric probability to either hypothesis being correct as it can only assign probabilities to things that have long run frequencies and the a particular hypothesis is either true or ot isn't. However, that is exactly the form of answer we actually want, which is why the p-value is so often misinterpreted that way. That makes it very difficult to give an accessible answer to the question that is also correct as statistical significance simply doesn't mean what people think it means. JMurphy Absolutely, I gave him the benefit of the doubt, but he showed he was a denialist by being unwilling to engage with the substantive technical criticism of his methodology. The hubris was priceless, though ;o) -
Tom Curtis at 00:30 AM on 16 June 2011Phil Jones - Warming Since 1995 is now Statistically Significant
Dikran Marsupial @77, certainly the deniers could have misrepresented Jones as you indicate if he had replied as I suggest. The issue is not whether what he said can be misrepresented, as everything can. The issue is how clear is it that it is a misrepresentation for those seeing the initial quote. In the instance where deniers had tried your suggested response, they leave themselves open to the obvious counter response that of course it is inappropriate to base claims on data that is not statistically significant; that that is why Jones bases his claims on thirty year trends which most certainly are warming, and are statistically significant; but that he was asked about a particular period which was only being discussed because deniers cherry picked a short interval to misrepresent the actual trend. The issue has then become the thirty year trend, and denier cherry picking rather than obscure arguments about which definition of "significance" is being used. Having said that, while I do believe that Jones could have answered better, I am in no way inclined to condemn him for that. As can be seen by this discussion, it is by no means easy to formulate an answer that is difficult to misrepresent, and far more so when doing so on the fly. And as I previously noted, and contrary to John Russell, even pausing to think can be misrepresented by hostile editing, so answering on the fly is more or less necessary. Where I do part ways with you, and agree with John Russell is that because it is always possible to answer better, I think media training would be useful for climate scientists who are often called upon to front the media. -
Bob Lacatena at 00:25 AM on 16 June 2011The greenhouse effect is real: here's why
27, Chris G, Yes, but with error bars. That is, I suspect someone out there may have the knowledge to quantify this properly... it's just that I don't, and can't find it. At the same time, I do think that putting together all of the expected differences, no matter how vague individually (poles, winters, radiation measurements, stratospheric cooling, etc.) might produce a final answer with very small error bars. Really, I think there's a whole scientific paper in there that needs to be written, to consolidate and properly quantify the evidence. Except I think that's only of interest to combating denial, and not really of interest to the scientists who don't feel the need to prove that... they've got better things to work on. [This came up in past months, on another thread, and there's a graph there in the post or in the comments that shows an increased diurnal effect coincident with expected AGW, so maybe the fuzziness isn't as great as imagined. But I can't seem to find it.] Again, I think it all comes down to proper quantification, rather than eyeballed, rule-of-thumb logical inference. [Last note... stratospheric cooling is, to me, sort of a show stopper. Nothing else causes stratospheric cooling, as far as I know, so right there, there's no real need for everything else, except that a wealth of evidence is always preferable in any case.] -
Tom Curtis at 00:18 AM on 16 June 2011Phil Jones - Warming Since 1995 is now Statistically Significant
Sorry, misplaced my second paragraph in 107 while editing. It should be placed at the end of the above comment (where it makes more sense). -
KR at 00:16 AM on 16 June 2011Phil Jones - Warming Since 1995 is now Statistically Significant
I think I would have said something along the lines of: "The 'statistical significance' test is 95% confidence, which is to say one chance in 20 that your data shows the trend incorrectly, that it's instead your null hypothesis plus noise. For that 15 year period the confidence is ~93%, or about one chance in 14 that the data doesn't correctly reflect the trend, so while it's suggestive, that short time frame doesn't meet the generally used significance criteria." -
JMurphy at 00:15 AM on 16 June 2011Phil Jones - Warming Since 1995 is now Statistically Significant
Dikran and others, I fear you are wasting your time with MoreCarbonOK - you only have to look at his website, to see classics like this : A short summary of the basic results of my study: CO2 is insignificant as a greenhouse gas. CO2 is not a poison or a pollutant. CO2 is one of the two main building blocks of ALL plant life on Earth. CO2 concentration has been up to ten times higher in the past CO2 is good. To start off with, I found Svante Arrhenius' formula completely wrong... It appears that we have not even yet reached the level of warmth compared to previous warm periods in known history, such as for example, the Medeviel Warm Period (MWP) - 1000 years ago, when Greenland was really green. See here: (Link to WUWT removed) Now the opposite, global cooling, that really is something to worry about.... There are some people there who make admirable attempts at showing him where he is going wrong, but there are none so deep in denial as those who believe that they have the secret answer and who believe they are more intelligent than the rest of us mere mortals ! -
Tom Curtis at 00:15 AM on 16 June 2011Phil Jones - Warming Since 1995 is now Statistically Significant
MoreCarbonOK, I checked your site and the source of your data, which is not an official source. To compare the data with official sources, I checked the Australian Bureau of Meteorology (BoM) statistics for Brisbane Airport. The clear conclusion is that your analysis of Brisbane temperatures is wrong. To what extent this is due to dodgy data, and to what extent due to statistical errors as identified by Dikran Marsupial I cannot say. The first thing I noticed is that the station identification numbers do not match. Nor is the station identification number used by your source used by BoM for any station. Further, there are slight differences in the specified location as to longitude and latitude. Checking nearby stations, I determined that your site was closer to Brisbane Airport than to other nearby BoM sites (Cape Moreton, Brisbane City, Archerfield and Amberly). So if the numbers you have come from an official BoM site, they do come from Brisbane Aerport. I then proceeded to check the daily values for May, 2011. I noticed that your figures differ from the BoM figures with regard to Minimum Temperature and Relative Humidity for May 1st; on Relative Humidity for May 2nd; Minimum Temperature and Relative Humidity on May 3rd; and on Minimum Temperature for May 4th. I did not bother checking any further. For just 12 values, your sight differed from BoM figures for 6 of those values. It is a reasonable presumption, therefore, that your analysis is based on faulty data and cannot be assumed to accurately reflect reality. For the record, BoM calculates trends and means for Brisbane Airport. For the period 1910 to 2010, the the mean temperature shows a positive trend of 0.04 degrees C per decade; the Minimum Temperature shows a trend of 0.11 degrees C per decade, and the Maximum temperature shows a trend of - 0.02 degrees C per decade. Almost all of the cooling in the Maximum trend was between 1910 and 1960, with the trend in the last half few decades of the twentieth century being positive. The greatest trend in the mean temperatures has also been in that period, but the greatest trend in minimum temperatures was in the period 1960 to 1990. Obviously the diurnal temperature range has narrowed over the preceding century (-0.13 C per decade) although recently it has widened noticeably. -
Bob Lacatena at 00:12 AM on 16 June 2011Forecast: Permanently Hotter Summers in 20-60 years
37, Eric the Red, My goodness, did you even read the link you sent? It completely destroys your position. Apparently I have to be more specific with you. Please provide an exact quote, by Dr. Latif, which supports your claims about his position on the matter. If you can't, just drop it. It's OT. Actually, even if you can, just drop it, it's OT. And this isn't the place to discuss the fact that solar activity as long since been eliminated as a factor in recent warming, or the silly and unscientific approach of clinging to magical decadal oscillations as some sort of reason to ignore CO2 levels. As Albatross said, time to get back on topic. If you want to keep posting about Latif, you can do so here, but don't expect me to join you. Your position is absurd to the nth degree and rebutting such complete nonsense holds no interest to me. -
Chris G at 00:04 AM on 16 June 2011The greenhouse effect is real: here's why
Scaddenp, I noted that as well, but decided I'd let Arkadiusz find truly relevant articles since I did not find a quick counter in Google scholar. But also, I still did not get it right at #25. If the source of the extra C in the past was methane from permafrost or clathrate, then the 13C / 12C ratio would be the same as fossil fuels. So, even if you showed that the increases that occurred in pre-history had the same isotope signature of the fossil fuel release currently, I'd think that would only be an indication of an organic source of the carbon instead of something like a flood basalt. In any event, I think Sphaerica has it. Everything is tied together and it would be difficult to ferret out the signature of the initial trigger. It might be safer to stick with a simpler narrative that we know we are releasing carbon with X isotopic ratio, and the ratio in the atmosphere (and ocean) has shifted to look more like X than it did. We know that CO2 inhibits the outbound flow of LW energy, and that there is no "saturation" level. Then add in that we have already seen all the indications of a warming world. -
Eric the Red at 00:02 AM on 16 June 2011Forecast: Permanently Hotter Summers in 20-60 years
Sphaerica, I have not been able to link to the audio directly, but you can access both the powerpoint presentation and accompanying audio here: http://deepclimate.org/2009/10/02/key-excerpts-from-mojib-latifs-wcc-presentation/ Do you really believe that temps will rise in a true solar minimum? IF that is the case, then we can once and for all eliminate solar activity from the climate forcings. The same can be said for decadal oscillations. -
MoreCarbonOK at 00:01 AM on 16 June 2011Phil Jones - Warming Since 1995 is now Statistically Significant
Henry@Bern I am sure my results are repeatable, but it is a lot of work. Don't think you can do it in 5 minutes. Forget about confidence intervals, you re. to it means you have not understood my method. You have to get access to the original reported data and plot the average reported monthly values against time. You can do that in Excel, which affords you to quickly get the trendlines. As an example, here is one of the first stations that I evaluated. It is an island that lies south of South Africa. this is how you must do it. http://www.letterdash.com/HenryP/marion-island-assessment-of-climate-change-in-the-southern-indian-ocean-due-to-the-increase-in-greenhouse-gases -
MoreCarbonOK at 23:38 PM on 15 June 2011Phil Jones - Warming Since 1995 is now Statistically Significant
@Eric The link reports that the file is damaged. I should report that it has not happened often on my pool table that minima were rising higher except for in the case of Honululu, which, as I said before, could be due to volcanic action. The minima in the arctic (Norway) was also slightly higher but only just. All in all, the maxima rose a lot faster than minima. And that means the warming is natural. @Dikran Dikran says: I have a long list of peer-reviewed journal articles on statistical methodology, and so I find your hubris rather amusing (-Inflammatory and ideology snipped-).Moderator Response: (DB) Please take care to formulate your comments to better comply with this site's comment policy. -
Albatross at 23:38 PM on 15 June 2011Forecast: Permanently Hotter Summers in 20-60 years
Eric @34, As I demonstrated @30, you misrepresented his talk at WCC3. Anyways, can we please (pretty please) get back on topic. -
Bob Lacatena at 23:24 PM on 15 June 2011Forecast: Permanently Hotter Summers in 20-60 years
34, Eric the Red,Prof. Latif stands by his statements and predictions, and that we should not open the champaign until...
Citation, please. Evidence. I have seen nothing except frustration from Dr. Latif at how deniers misrepresent his statements and work, so you have to come through on supporting this, or else this is a particularly egregious and unforgivable inaccuracy on your part....the potential for unpredictable external influences and the recent press release concerning the potential for a another solar minimum.
Citations please. Evidence. And I don't care about press releases, I care about scientific studies. A vague insinuation based on an anonymous press release is meaningless (and desperate). [And what do you think happens if we do have a solar minimum, temps rise but not as much, so we foolishly burn even more CO2 because people like you think everything looks just wonderful... and then the solar minimum ends? And when we finally cut back, the negative aerosol feedback ends? What exactly are you arguing for? Hesitate and be fooled into allowing an ultimate 6˚C temperature rise?] -
Eric (skeptic) at 23:08 PM on 15 June 2011Phil Jones - Warming Since 1995 is now Statistically Significant
MoreCarbonOK, I can't find Easterling's 2005 paper online. Here's a paper that references that paper and uses some of that data (showing minimum temperatures rising faster than maximums): http://ams.confex.com/ams/pdfpapers/100659.pdf -
Eric the Red at 23:07 PM on 15 June 2011Forecast: Permanently Hotter Summers in 20-60 years
Sphaerica, Prof. Latif stands by his statements and predictions, and that we should not open the champaign until we see whose projections better match the climate observations. I will not admit a mistake, as I have not misrepresented his predictions. However, I will move on. Interesting is the timing of this discussion about Latif's work concerning the potential for unpredictable external influences and the recent press release concerning the potential for a another solar minimum. -
Dikran Marsupial at 22:59 PM on 15 June 2011Phil Jones - Warming Since 1995 is now Statistically Significant
Bern, that answer is better than most, but again what happens if the interviewer thinks it is too indirect and presses for a definitive answer. Then you end up having to say "no it is not significant", but you have made it look as if you had made a concession and had been evasive. Note it is also pretty much what Jones actually said, other than having started by giving a direct answer. Nothing Jones actually said implies that it hadn't warmed since 1995, but the Daily Mail reported it that way anyhow. Note Jones actually said a bit later in the interview "I'm 100% confident that the climate has warmed", so the quote is there. N.B. If he said specifically that it had warmed since 1995 he would again be accused of scientific malpractice as you are not supposed to claim that something exists based on a failed test of statistical significance. It is the fault of hypothesis testing, which is rather broken in the way it is applied in science. -
Bern at 22:52 PM on 15 June 2011Speaking science to climate policy
What's the residence time of aerosols compared with that of the other GHGs? If they're not too dissimilar, then it'll even out even if we cut emissions of aerosols. Assuming, of course, that human emissions are the only source of the other GHGs, which seems perhaps incorrect given the permafrost melt going on. Either way, just considering the CO2 forcing (and the fast feedbacks) would give a lower bound for the committed warming, right? -
Bern at 22:46 PM on 15 June 2011Phil Jones - Warming Since 1995 is now Statistically Significant
Dikran: perhaps a better answer would be along the lines of, "Over that interval, the warming trend is only 93% significant, which doesn't meet our usual standard of 95% significance." Correct, answering the question (if slightly indirectly), and with a much better chance of letting the audience know it's only *just* failing the significance test, but the trend is definitely still upwards. Of course, you'd say that would be reported as "[it] doesn't meet our... standard", and you'd probably be right, too. But it'd be a lot harder to spin it into "Phil Jones says it hasn't warmed since 1995", given that there's a clear statement that it *is* warming. Pointing back to the original quote would highlight the amount of word-twisting that had to go on to get the desired headline. -
Dikran Marsupial at 22:44 PM on 15 June 2011Phil Jones - Warming Since 1995 is now Statistically Significant
MoreCarbonOK ROTFLMAO, as it happens my field of research is a branch of statistics, and I have a long list of peer-reviewed journal articles on statistical methodology, and so I find your hubris rather amusing! Do note however that I have pointed out two specific flaws in your analysis, and for all of your bluster, you haven't even attempted to address either of them. That speaks volumes for the strength of your analysis. -
Bern at 22:40 PM on 15 June 2011Phil Jones - Warming Since 1995 is now Statistically Significant
Ok, my stats is rustier than the Titanic, but I downloaded the data for Amberley, Australia, from the BoM. I used Amberley (35km west of Brisbane) as the BoM page was telling me the Brisbane airport station only opened in 1992 (the old one closed in 2001), whereas Amberley is continuous back to 1941. Ran some analysis in LibreOffice, and the 37-year least-squares linear trends are very similar to what MoreCarbonOK lists for Brisbane. Except... the standard errors ranged from 29% to 312% of the trend magnitude. For the one month that got a negative trend (December), the trend was -0.011 +/- 0.045 (95% conf interval). That's one hell of an error bar, and a good reason why real climate analysis looks at more than one site. Interestingly, the trends were highest in the cooler months, and lowest in the warmer months. More-or-less what you'd expect from greenhouse warming... :-) -
Dikran Marsupial at 22:38 PM on 15 June 2011Phil Jones - Warming Since 1995 is now Statistically Significant
John Russell I can be convinced, all it would take is for someone to make a suggestion of an answer that I can't pick significantholes in. I am pretty sure that no such examples can be found, but it would only take one example to prove me wrong. If I can find a way of misinterpreting the answer, you can be sure the Daily Mail can! Media training is vital for any scientist that need to have contact with the press, but nothing can provide a 100% bulletproof defense. -
John Russell at 22:33 PM on 15 June 2011Phil Jones - Warming Since 1995 is now Statistically Significant
Dikran -- OK, I guess I'm not going to convince you that there is a better way to give the same honest answer as Jones did, but in a way that is less likely to play into the hands of those wishing to deny. I wish we could go back in time and I could give him a bit of training. The answer would still be up to him, of course, but perhaps he would see there would be better ways of expressing it so as not to give the Daily Mail their headline on a plate. -
MoreCarbonOK at 22:28 PM on 15 June 2011Phil Jones - Warming Since 1995 is now Statistically Significant
@Dikran says: "Of course none of that changes the fact that your analysis is statistically nonsense and that you refuse to address statistical criticism of it". My method of statistics is sound as it is the way it should be done. If you want to evaluate ground stations you have to determine the exact slopes from the trendlines that will tell you the temp. increase noted over time. You want to tell me that that is ridiculous? I put it to you that either you do not want to hear the truth or you are just plain ignorant. You can either can stay in your ignorance (and that of the IPCC) or you can learn something from me: http://www.letterdash.com/HenryP/more-carbon-dioxide-is-ok-ok It is your choice. -
bartverheggen at 22:24 PM on 15 June 2011Speaking science to climate policy
The numbers and reasoning is taken from Ramanathan and Feng (2009). Total greenhouse forcing is 3 W/m2, which exists approx half of CO2 and half of the other GHG's. With a sensitivity of 3 deg per doubling (or 0.8 deg per W/m2) this comes to 2.4 deg. -
Dikran Marsupial at 22:18 PM on 15 June 2011Phil Jones - Warming Since 1995 is now Statistically Significant
John Russell That is pretty much my point, we can all make suggestions, but they will end up not being any better than Jones' from the point of view of how they will be misrepresented by the media. Remember the skeptic media has access to scintists who can advise them of how they can spin whatever is said. For the first possible answer, that would come accross as extemely condescending (even if true) and evasive, and again you would end up with the skeptic media saying that this was the killer question that Jones wouldn't answer. In the second case, the interpretation is incorrect (as I pointed out earlier in the thread) and you will end up with the skeptic media saying that Jones did not understand statistical hypothesis testing. We are on the same side, I'm just pointing out that it (this particular question) is a no-win situation, mostly because statistical hypothesis testing (as is commonly performed in science) is deeply counter-intuitive. -
MoreCarbonOK at 22:16 PM on 15 June 2011Phil Jones - Warming Since 1995 is now Statistically Significant
Skywatcher says: "I assume you're cherrypicking stations that appear not to show a trend?" I only started in the SH because I live in the SH. I found no warming in the SH. No cherry picking. Everything was random. Why don't you check it out yourself? I must warn you: It is a lot of work. Gathering the data from the station and putting it in Excel. But perhaps you can get some students to help you? I only later picked up on a trend of no warming in the SH and more warming in the NH. You tell me why. Anyone? I am just as puzzled about that. It means that I now have to balance my pool table. Equal no. of SH and NH. It is just like playing pool again!!! http://www.letterdash.com/HenryP/henrys-pool-table-on-global-warming -
John Russell at 22:09 PM on 15 June 2011Phil Jones - Warming Since 1995 is now Statistically Significant
Dikran -- hey man, I'm not a scientist so I can only make suggestions. OK, here's another way to answer. The interviewer asks; "Do you agree that from 1995 to the present there has been no statistically-significant global warming?" Possible answer: "Does the audience understand the scientific meaning of 'statistically-significant'? Because without understanding that phrase my answer is likely to confuse." Interviewer says (though I think it's unlikely): "It means that there's a probability of 95%." Scientist response: "Precisely" (or whatever needs to be said to establish that statistically significant means a 95% probability). "In fact the statistics give us 92.8%, which I'm sure we'd all agree is a pretty high level of probability -- though perhaps not quite the level that scientists would call the 'statistically significant' level of 95%. So, does that meet the Dikran test? -
Dikran Marsupial at 22:05 PM on 15 June 2011Phil Jones - Warming Since 1995 is now Statistically Significant
MoreCarbonOK wrote: "I was only interested to find out if anyone here has any idea as to why there seems to have been no actual warming in the southern hemisphere whereas the warming in the northern hemisphere is clearly more pronounced." which is, shall we say, rather inconsistent with your earlier statement: ". I said that it does not make any difference whether or not there was any significant warming if it can be proved (as I have done) that the warming is natural and not man-made." It isn't even true that there has been no SH warming, as has been pointd out to you already. If you really want to know the answer to that question, then why not read the chapter on regional climate change in the IPCC WG1 scientific basis report? I suspect the difference in land cover is a large part of it. The southern oceans have a massive thermal inertia, which will be buffering the SH from AGW more than the NH, which has less ocean. Of course none of that changes the fact that your analysis is statistically nonsense and that you refuse to address statistical criticism of it. -
MoreCarbonOK at 21:55 PM on 15 June 2011Phil Jones - Warming Since 1995 is now Statistically Significant
@Eric From opening the link that you gave, I cannot see the (original) data & info only an abstract. -
MoreCarbonOK at 21:50 PM on 15 June 2011Phil Jones - Warming Since 1995 is now Statistically Significant
@Dikran See 74 again I was only interested to find out if anyone here has any idea as to why there seems to have been no actual warming in the southern hemisphere whereas the warming in the northern hemisphere is clearly more pronounced. Anyone? -
Eric (skeptic) at 21:39 PM on 15 June 2011Phil Jones - Warming Since 1995 is now Statistically Significant
MoreCarbonOK, what do you think of this study http://www.agu.org/pubs/crossref/2005.../2005GL024379.shtml -
Dikran Marsupial at 21:37 PM on 15 June 2011Phil Jones - Warming Since 1995 is now Statistically Significant
John Russell Had Jones answered that way, he would be subject to the criticism that a lower standard of statistical evidence was required for evidence infavour of AGW than was required of evidence against the mainstream position. The Daily mail would be reporting "Double Standard by IPCC Scientists Exposed". Jones had not performed a U turn, but that didn't stop the press reporting it that way. -
Dikran Marsupial at 21:33 PM on 15 June 2011Phil Jones - Warming Since 1995 is now Statistically Significant
MoreCarbonOK From your comment here: "Every month of the year at a weather station treated as a new test." From your the link you provided to your website: "The first result clearly shows that there has been no significant warming in Brisbane during the past 35 years." In both cases, emphasis mine. So, you still have not addressed the point that data for individual station data cannot be used for reliable estimation of secular trends, you have not addressed the point that looking at a multitude of trends in the way that you do is a recipe for cherry-picking (c.f. multiple hypothesis testing problem), and all you want to do is try and evade the point about your incorrect usage of statistical terms. The inability to address (never mind accept) criticism is what makes someone a denier rather than a skeptic. It is your choice. -
skywatcher at 21:33 PM on 15 June 2011Phil Jones - Warming Since 1995 is now Statistically Significant
#82, you're falling into the massive trap of cherry-picking your data. One could ask why you picked your selected 'random' sites from around the world, but you fail because you don't aggregate sites together to remove the variability of weather, as Dikran has stated several times. From Braganza et al, 2004: "Observed DTR [Diurnal Temperature Range] over land shows a large negative trend of ~0.4C over the last 50 years that is very unlikely to have occurred due to internal variability. This trend is due to larger increases in minimum temperatures (~0.9C) than maximum temperatures (~0.6C) over the same period." And a quote from Alexander et al, 2006: "When averaged over the globe, almost all of the temperature indices show significant changes over the 1951–2003 period. Trends in temperature indices, as detailed below, reflect an increase in both maximum and minimum temperature. There is also generally a much larger percentage of land area showing significant change in minimum temperature extremes than maximum temperature extremes. The magnitude of the trends is also generally greater for minimum temperature related extremes. This finding is in agreement with previous studies using monthly global data, e.g., Jones et al. [1999] and regional studies using daily data, e.g., Yan et al. [2002]." Funny you suggest that the southern hemisphere is not warming either, in HADCRUT3 it shows a steady and significant warming trend, check woodfortrees for the data. The aggregated signal for Southern Hemisphere stations is clear warming. I assume you're cherrypicking stations that appear not to show a trend? -
Eric (skeptic) at 21:32 PM on 15 June 2011Phil Jones - Warming Since 1995 is now Statistically Significant
I assume the null hypothesis of Jones is that GAT is not changing? That appears easy to disprove using each monthly GAT change as an independent test. But each monthly change is not an independent test because there is lots of autocorrelation (here is a made-up example: http://www.duke.edu/~rnau/411trend.htm) IOW, GAT might increasing "since 1995" because it shows 16 year increases (and decreases) over the entire record (~120 years of monthly GAT) so the current rise is not unusual. My question is, if some statistical test can determine the significance of the "since 1995" rise in the context of the whole record, doesn't that become a test for natural variability? -
John Russell at 21:30 PM on 15 June 2011Phil Jones - Warming Since 1995 is now Statistically Significant
Dikran writes: "What if the interviewer presses for a direct answer "so the increase in temperature is not statistically significant then?"." Easy. If pressed by the question you suggest, you respond, "Yes, it is, 1995-2009 is statistically significant at a 92.8% confidence level." You can be pretty sure that any reporter will have to accept that, as they don't know anything about significance levels. Whether the bloggers afterwards try to make something of it is irrelevant; at least the Daily Mail doesn't print that you've done a 'U' turn. -
Eric the Red at 21:29 PM on 15 June 2011Speaking science to climate policy
Bart, how did you arrived at a current "committed" value of 2.4C? It appears that you are attributing higher warmer to the gases other than CO2. Is this correct? -
MoreCarbonOK at 21:21 PM on 15 June 2011Phil Jones - Warming Since 1995 is now Statistically Significant
@Dikra But I did say that not. Just go back to 74. I said that it does not make any difference whether or not there was any significant warming if it can be proved (as I have done) that the warming is natural and not man-made. So the whole argument about the confidence interval is a non-issue. You think that it not on tpoic? I say that the actual global warming can be easily assessed and is in the region of ca. 0.02 degrees C annum since 1974. It is accompanied by a reduction in humidity of ca. 0.02% per annum since 1974. But it not the minimum temps that have pushed up the global temp. It was the maxima. So the global warming is natural. It as easy a pie. Check it out yourself. http://www.letterdash.com/HenryP/henrys-pool-table-on-global-warming -
Dikran Marsupial at 21:02 PM on 15 June 2011Phil Jones - Warming Since 1995 is now Statistically Significant
MoreCarbonOK O.K., so if you are not doing formal hypothesis test, you should not use the words "test" and "significance" with relation to a trend as that is what those words imply. You should know that from stats 104. You will also note that the topic of this article is statistical significance. Secondly, even if you are not performing formal hypothesis tests, the multiple test issue still applies to informal test. If you test enough you will always be able to find the result you want. That doesn't mean that the argument is correct. It is a recipe for cherry picking (whether inadvertant or deliberate). You still have not addressed the point that you can't use station data to detect the secular variation known as climate. Calculating trends separately for each month only makes that problem worse. Read the articles by Glen Tamblyn that I pointed out to you, and if you think your method is better, then lets discuss it on that thread. -
MoreCarbonOK at 20:40 PM on 15 June 2011Phil Jones - Warming Since 1995 is now Statistically Significant
MoreCarbonOK@dikran You do not get it yet. There is no hypothesis testing going on here. All the slopes (inclines or declines) measured are for real and they show real history. Mostly taken from 1974. I don't trust the data from long before that. Perhaps start here: http://www.letterdash.com/HenryP/more-carbon-dioxide-is-ok-ok until you get to the point where you see why and how we started my pool table on global warming.
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