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Comments 1 to 50 out of 103:

1. Marcus at 13:28 PM on 16 February, 2010
   Actually, John, it's funny you should mention this. On Media Watch here in Australia, they made reference to the supposed claim by former IPCC director-Sir John Houghton-that "Unless we announce disasters no one will listen,". Turns out that the first actual use of that "quote" (supposedly from 1994) was actually 2006-by an Australian journalist by the name of Piers Ackerman. He claimed he got the "quote" from Houghton's book "Global Warming, The Complete Briefing". Guess what, though? That quote does *not* exist in *any* edition of that book-so its just been invented, from whole cloth, by the contrarians to cast aspersions on those concerned with global warming! Personally, I hope Phil Jones sues the Daily Mail & I hope Houghton sues The Sunday Telegraph. Maybe if these newspapers (thought I hesitate to use the term for these rags) face a huge price for their slanderous comments, they might be less likely to make such comments in the future! Anyway, check out the full article here: http://www.abc.net.au/mediawatch/transcripts/s2820429.htm
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2. yocta at 13:29 PM on 16 February, 2010
   What's distressing about this article or maybe a sad reflection of its readership but: One of the comments most highly rated"(1510 votes) include: ...and so the scam of AGW begins to unravel! One of the comments most lowly rated has 1079 votes against containing the phrase: ... humans ARE having an impact on climate change.
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3. JonMoseley at 13:29 PM on 16 February, 2010
   Ah, NO.... You claim to be lecturing the public on lack of scientific understanding or knowledge, but your arguments are not scientifically correct. Any measured change or trend that is not statistically significant DOES NOT EXIST scientifically. What "statistically significant" means is that any apparent change is smaller than the accuracy of the means for measuring the change. Thus, scientifically, a trend that is not statistically significant DOES NOT EXIST, and must be treated as ZERO for the purposes of valid science. Furthermore, the observed results are in conflict with the predictions of the computer models. Therefore, the computer models are wrong. Since we have no experimental (i.e., scientific) data whatsoever to support the idea of man-made global warming, and are relying only on the computer models, the invalidity of the computer models destroys the entire global warming alarmist argument.
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   Response: "Since we have no experimental (i.e., scientific) data whatsoever to support the idea of man-made global warming..."
   
   Can I suggest you read the article to the end to see experimental data besides the HadCRUT record. Then I recommend Empirical evidence that humans are causing global warming.
4. JonMoseley at 13:32 PM on 16 February, 2010
   To be valid science, one must state that a measurement that is not statistically significant is equivalent to ZERO.
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5. bcbwilla at 13:33 PM on 16 February, 2010
   That was quick - you're on top of things! I've been seeing this article all over the place, and I became extremely frustrated after reading the original BBC interview and realizing that the Daily Mail was being less than honest with their headline. Although this is not Phil Jones' fault, I do think he should have been much more careful with his wording. Even though what he said is completely accurate and not controversial, it is confusing to those with little scientific knowledge and easy to twist by those who want to get a good headline. Perhaps he should have gone into a bit more detail to avoid such confusion. He appears to have underestimated the quote mining ability of others.
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6. jasonk at 13:39 PM on 16 February, 2010
   B - Do you agree that from 1995 to the present there has been no statistically-significant global warming Yes, but only just. I also calculated the trend for the period 1995 to 2009. This trend (0.12C per decade) is positive, but not significant at the 95% significance level. The positive trend is quite close to the significance level. Achieving statistical significance in scientific terms is much more likely for longer periods, and much less likely for shorter periods. C - Do you agree that from January 2002 to the present there has been statistically significant global cooling? No. This period is even shorter than 1995-2009. The trend this time is negative (-0.12C per decade), but this trend is not statistically significant. in (B) - is positive for an upward temp increase and there is 'almost' statistical significance with 1995 to 2009. a +0.12 up trend. in (C) - the 2002 to present shows a -0.12 down trend...but is not statistically significant because it is a shorter time frame. now, i am not a mathematician but i think if you add +0.12 with -0.12 the answer would be zero. no net gain or net loss...exactly zero. thus, how can things be warming +0.12 per decade and then cooling -0.12 per decade be interpreted as temperature gain? remember that: E - How confident are you that warming has taken place and that humans are mainly responsible? I'm 100% confident that the climate has warmed. As to the second question, I would go along with IPCC Chapter 9 - there's evidence that most of the warming since the 1950s is due to human activity. remember that 100% confident is still a 100% opinion. there is evidence that smoking can cause cancer but it is not 100% of time. is smoking good for any body? absolutely not. this is just an example that NOTHING in science is 100%. to say so is 100% subjective opinion.
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7. Marcus at 13:44 PM on 16 February, 2010
   Jon Moseley, I'm afraid that its you who is being unscientific. It is *extremely* difficult to get any kind of significance over such a small number of years, especially when there are so many things which can influence a single year-like the declining total solar irradiance we've seen over the last decade & individual El Nino vs La Nina events. However, if you look at a better time period (like 1979-2009 or 1950-2009) then you see a definitive warming trend which is statistically significant. Significant or not, its certainly not a *cooling trend* from 1995-2009 as some people have tried to claim, no matter how they try & cherry pick their dates!
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8. Marcus at 14:06 PM on 16 February, 2010
   jasonk, I just went & did a quick calculation using data from GISS, & what I show for 1995-2009 is a warming event of +0.015 degrees per year, with an R-squared value of 0.41 (just below the 0.5 needed to be statistically significant). If I look at 2002-2009, I get a cooling event of only -0.003 degrees per year, with an R-squared value of only 0.02. If I look at 1995-2002 I see a warming event of +0.02 degrees per year, with an R-squared value of 0.22. So we have 2 relatively significant warming trends (1995-2009 & 1995-2002) vs a relatively *insignificant* cooling trend (2002-2009). So I'm curious as to what your point is? Well, aside from the dangers of cherry picking extremely short time frames! I'm much more interested in the trend for 1979-2009 (+0.016 degrees per year, R^2=0.709) & for 1959-2009 (+0.013 degrees per year, R^2=0.762).
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9. stevecarsonr at 14:08 PM on 16 February, 2010
   The ocean heat content graphic is nice. The whole idea of measuring the "temperature" of the earth by averaging (area weighted) air temperatures 6ft off the ground (a proxy for surface temperature) with (area weighted) sea surface temperatures is just such a crazy idea. I realize the OHC has been hard to come by and even now deep ocean heat is a problem.. but still. The heat capacity of the atmosphere is 1/1000th of the heat capacity of the ocean.
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10. hallewis at 14:41 PM on 16 February, 2010
    This is statistical garbage, and I find it hard to believe that he doesn't know it. To say that something isn't statistically significant at the 95% confidence level, but would be if you look a longer sample is to predict that you know what the longer sample will be, which in turn means that you take the lower significance as significant. He seems (as quoted. and I grant that he may have been misquoted) to have a limited knowledge of statistics.
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11. David Horton at 14:43 PM on 16 February, 2010
    It is as if he is having a polite chat in a seminar with colleagues who understand the subtleties of statistics and regression lines and variability and natural variation masking trends. He must surely have known that saying this on tv in the way he did would feed the deniaworld crazies?
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12. ejo60 at 14:56 PM on 16 February, 2010
    I have lost my confidence in some media because they are making too many errors in reporting climate science. Also, I refuse to believe their errors are bad luck, it seems more like harassment by an overactive anti IPCC lobby group. In the Netherlands it is the Telegraaf and Elsevier that show this behavior. My policy is to avoid those media, moreover if you need to say something then insist that they start with a written press release and that you get to see their text prior to publication.
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13. Tom Dayton at 15:06 PM on 16 February, 2010
    hallewis, the consideration of the length of sample needed to detect a signal against the noise is an example of statistical power. It is a completely legitimate and important topic in statistics, but one that typically is not covered adequately, if at all, in high school and even college statistics and science classes. Here is just one of many introductions to statistical power. Phil Jones does not have a "limited knowledge of statistics." His comments were completely appropriate.
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14. mazibuko at 15:38 PM on 16 February, 2010
    There is much to do in the comments here about statistical significance. The post and some commenters have rightly pointed out that it is harder to reject the null hypothesis when sample sizes are small, particularly if the effect (in this case the trend in temperatures) is small. Two other points worth mentioning: 1. the significance level chosen for rejecting the null hypothesis is somewhat arbitrary; 2) choosing a particular null hypothesis entails making assumptions. Regarding the first point, Dr. Jones used the conventional 95 % threshold. What if he had selected 90 %? The trend might well be significant at that level. One the second point, choosing to test for whether the climate has warmed over the past 15 years (null hypothesis: there has been no change in global temperatures over the past 15 years) does not seem like a particularly useful test, given that climate is typically defined as the average conditions over 30 years. Finally, many branches of science (e.g. applied ecology) are moving away from hypothesis testing, in large part because of the aforementioned arbitrariness, and increasingly relying on Information theory, predictive ability, and related approaches.
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15. bigelowe at 16:19 PM on 16 February, 2010
    John, Just so that I'm clear on this....the HADCRUT data, and the data Jones refer to, are measurements of both land and marine surface areas. The chart you have on the bottom includes energy accumulated in deeper areas of the oceans, which are not included in the other measurements. Is this correct? I was a little unclear on this point. If anyone else knows the answer, feel free to confirm. Also, what is the reason that temperature of the oceans is not included along with the rest. Is this because of inadequate monitoring, or for some other reason? Thanks,
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    Response: Figures 1 and 2 are measurement of surface temperature, both land and ocean, in degrees Celsius. Figure 3 is a different metric - it's a measure of heat content, in Joules. What is the relation between surface measurements and total heat content? See the tiny red sliver in the total heat content graph? That's the portion of global warming that goes into heating land + atmosphere. Note that only part of this goes into warming the atmosphere - the energy to melt ice and heat land is also included in the red area.
16. stevecarsonr at 17:26 PM on 16 February, 2010
    - #15 bigelowe: The global temperature indices are only measuring surface temperature of land and sea. The top few mm of the ocean. So the HADCRUT, GISS, etc don't measure Energy (Let's see if html tags work..) Which is a problem because that's really what everyone is interested in (everyone in climate). Obviously surface temperature is a function of energy but in very derived and convoluted ways. For example, during ENSO events, colder water gets pushed up to the surface and we say "global temperatures have gone down". In fact, probably the total ocean energy is the same, and more likely to be going up for a few months or years because less heat is radiated out from the oceans now the surface is colder. The reverse is true. Because we only measure the surface temperature we are measuring quite a random or unpredictable variable. Especially as the oceans are 70% of surface area and therefore weighted to 70% of global temperatures. But it's hard to measure OHC (ocean heat content). I read a climate guru recently (can't remember his name) saying that they had more confidence in global temperature measurement than OHC measurement. Although he implied but didn't really say whether consequently it was more use. The Argo project now has about 3000 sensors around the oceans collecting temperature and salinity data down to 2km. They started being deployed late 90's but really have only fully been in place for a few years. And they don't measure below 2km. In the past there were lots of measurements of vertical temperature profile in the oceans done using XBTs but then someone found out that they had some biases (don't really know the story on that one) and consequently a lot of the old numbers that had been collected have issues. I think that once we have our hands around OHC much more of the climate will be understandable. This should also be the measurement that is the headline number and graphic everywhere, not the "surface temperature". Just my opinion.
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17. Jeff Freymueller at 17:48 PM on 16 February, 2010
    #6 jasonk, part of the reason for your confusion is that neither of the rate estimates include the uncertainty. Estimates should always include the uncertainty -- that's the only way you know how good the estimate is. The uncertainty is half of the answer. In this case, the uncertainty in the 2002-2009 rate would be about 2-3 times as large as the uncertainty in the 1995-2009 rate, depending on the noise characteristics of the data. The larger the uncertainty, the lower the confidence level that the estimate is significantly different from zero.
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18. Jeff Freymueller at 17:54 PM on 16 February, 2010
    #10, hallewis. Jones did not say what you seem to think he said. Please reread: "Achieving statistical significance in scientific terms is much more likely for longer periods, and much less likely for shorter periods." This is a general statement, and completely true, because the uncertainty in the rate will be higher for shorter periods. He did not make any claim about what the significance for 2002- beyond 2009 would be if there were more data recorded. But if you took earlier data, say 1980-2009, then the data would show a warming trend at a very high level of confidence, easily surpassing the 95% confidence level that is usually used.
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19. Bern at 18:09 PM on 16 February, 2010
    John, is it possible to include a chart showing the estimated cooling/warming rate for the two periods (1995-2009 & 2002-2009) along with the error range for each? I think that might be educational. Not sure how to represent it, though - perhaps a column chart showing the upper & lower bounds of the uncertainty interval for 90 & 95% confidence, and the nominal rate in the middle? (Don't know if you have the data for that, though)
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    Response: I was mulling whether to do a follow-up post on statistical significance over different periods - I may do one tomorrow. I do have the data for that. Thanks for the suggestion.
20. Steve L at 18:25 PM on 16 February, 2010
    Re #14, mazibuko -- good points. You might add that power analyses should be employed when trying to determine an appropriate choice of alpha prior to hypothesis testing. Hmmm, I can't find the reference I want right now. Here Tamino has some information on the amount of noise versus signal to expect for these kinds of tests. Another consideration is the issue of whether or not one is testing a one-tailed or two-tailed null hypothesis. The link above (hopefully it works) shows a two-tailed confidence interval. I don't know if Jones' test was one- or two-tailed, but really it should have been one-tailed. A one-tailed test is more powerful (more able to reject the null hypothesis). Almost finally, independent from the issue of signal versus noise, there is the issue of what's special about 15 years for this particular test. Hypothesis testing requires that the test be constructed a priori. It's invalid to watch as data are added, going forward in time, and then to make simple conclusions (ignoring the non-independent tests that have already occurred) when a calculated p-value finally goes above or below 0.05. That is, you can't cherry-pick the time frame. Finally, JonMoseley in #3 might do well to construct another hypothesis test: Ho = the rate of warming does not differ significantly from a rate of 0.2 C/decade. Failing to find significance there means, if you apply Moseley's funny interpretations of statistical rules, that differences with consensus expectations of AGW do not exist.
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21. Riccardo at 18:59 PM on 16 February, 2010
    The question asked by the BBC journalist had clearly the intention to be equivocal. Indeed, 1995 is the last year for which there is not a statistical significant trend. It's easy to make a trend not statistically significant, just make it short enough, but it can not disprove (nor prove) anything. If you want to clarify the recent apparent slow down of temperature increase a better question would be: "is the recent (apparent) slow down of the temperature increase statistically compatible with the long term trend?" The answer is a sound yes.
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22. Arkadiusz Semczyszak at 19:09 PM on 16 February, 2010
    Using the trend from 1995 - 2009 without the commentary is wrong. Because it covers the end of the transition from the cold phase in the warm AMO, which is always sharp. In turn, it is wrong to use the 1998-2009 trend - without taking into account the impact of EN(LA)SO.
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23. Arkadiusz Semczyszak at 19:49 PM on 16 February, 2010
    1. "No Comments" may be used at most trends: 70 + / - 10 years x n. They include most cycles: Gleissberg's; AMO+PDO, THC, EN(LA)SO. 2. Marcus repeats: the sun "expire" ... and the warming continues. However, the present warming is consistent with the millennium cycle. I recall a diagram: http://www.rni.helsinki.fi/research/info/sizer/fig2big.jpg; and I am adding a new: http://mclean.ch/climate/figures/GISP_to_4Kbp.gif. Present Warming is greater in NH than the SH. Rahmstorf has repeatedly said, that the Millennium cycle is dependent on the cycles of the sun - but not directly. So far, created a few theories to explain this relationship.
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24. Dikran Marsupial at 20:01 PM on 16 February, 2010
    JonMoseley says: "Any measured change or trend that is not statistically significant DOES NOT EXIST scientifically." No, that is incorrect (but a very common fallacy). If a measurement is not statistically significant it means there is insufficient evidence to reject the null hypothesis. In this case it means the trend is too small (w.r.t. the noise) to be confident that the trend is not zero. That is not at all the same thing as "the trend does not exist scientifically". Of course one would not build an argument solely on a non-statistically significant trend, but then again AGW theory has a much broader base of evidence and nobody (who understands statistics) would claim that a short term trend is proof of AGW. "Furthermore, the observed results are in conflict with the predictions of the computer models. Therefore, the computer models are wrong." Actually that is not correct either, see the paper by Easterling and Wehner, which shows that the internal variability of the climate means that there will be occasional decadal trends showing no warming or even cooling, and that these are seen in the output of the models. http://www.agu.org/pubs/crossref/2009/2009GL037810.shtml A common demonstration of the Dunning-Kruger effect in discussions of climate is a lack of understanding of what the models actually say.
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25. MarkR at 20:12 PM on 16 February, 2010
    JonMosely: do you have a reference for that claim so I can check? As I understand it, your precision may be near perfect, but the system may be intrinsically 'noisy' (eg El Nino is a real physical phenomenon, but in the context of looking for warming it contributes to 'noise'). So your precision may be enough to detect a trend, but without knowing how to fully account for all of the noise, you must treat it as such and determine based on the known high frequency noise in the data whether it is statistically significant or not. So Jones is right; there is a trend, but there is a 5%+ chance that it could have occurred from noise. Which is unsurprising, given that an ENSO switch is 0.4-0.7C in a few months and 'global warming' is a trend of 0.1-0.2C/decade atm and so people tend to talk about longer time periods. Please correct me if I'm wrong and point me towards where I can fix my understanding.
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26. MarkR at 20:23 PM on 16 February, 2010
    jasonk: The reason a shorter time frame is less statistically significant for the same trend is that noise tends to average to zero at longer time scales. this also demonstrates the effect. Also, it's less likely that noise will always 'add up' to a trend over 20 years than it will do so for a shorter time period. If you think of it as flipping a coin each time with heads meaning noise goes warmer, tails cooler, then it's clearly less likely and you can claim higher statistical significance. As for +0.12 -0.12 = 0, that's not how it works in trends. If you take 1995-2009 you get +0.12K/dec and this includes the 'cooling' period from 2002. It just so happens that 1995-2002 is a trend of +0.26K/decade. And you can't add trends anyway unless they're for equal time periods. Eg if you raise temperatures at +0.2C/decade for 50 years you end up 1C warmer than you were before. If you then cool at 0.2C/decade for 10 years, you'll only cool by 0.2C and you'll still be 0.8C warmer than you were 60yrs ago. The 60 year trend will remain positive, even though +0.2 - 0.2 = 0.
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27. Dikran Marsupial at 20:26 PM on 16 February, 2010
    Jon Moseley said: "To be valid science, one must state that a measurement that is not statistically significant is equivalent to ZERO." The thing to remember about statistical tests is that "absence of evidence is not evidence of absence". If you treat the trend as equivalent to zero you are saying that the lack of statistically significant evidence for a positive trend is evidence that the trend is zero, which is not correct. This is precisely the assumption you make when you criticized the models "Furthermore, the observed results are in conflict with the predictions of the computer models." For there to be a model-data conflict, the error bars of the observed trends need to be outside the spread of the modelled trends. If you did the comparison properly there is no conflict.
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28. 40 Shades of Green at 20:31 PM on 16 February, 2010
    Hi Would you have a link to either a Non Paywall version or a discussion of either or both of Murphy 2009 and Von Schuckman 2009. Many thanks 40 Shades
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29. 40 Shades of Green at 20:37 PM on 16 February, 2010
    To my mind the key question is this. If 15 years without statistically significant warming is not enough to give one pause, then how many years would be required. 20, 25, 30, 50, 100?
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30. John Russell at 20:41 PM on 16 February, 2010
    To revert to my analogy posted under another topic. It's like watching the last 14 waves that came in on the beach and trying to work out whether the tide is coming in or out. The variation in height of the last 14 waves does not give one enough information to produce a statistically significant trend (even less so the last 8 waves). The noise (waves) hides the trend (tide). After ten minutes and a hundred waves the direction of the tide becomes very apparent. I wonder why Phil Jones didn't think to use such a clear analogy? The lay audience would have got it in one and those with a basic scientific understanding would/could not have questioned the way he expressed himself.
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31. Riccardo at 21:14 PM on 16 February, 2010
    40 Shades of Green, there's no a priori time span. You need to perform statistical analysis on the actual data and determine it. Here's a draft of Von Shuckman et al. 2009..
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32. Marcus at 22:42 PM on 16 February, 2010
    Sorry, Arkadiusz Semczyszak, but your claims are not borne out by the numbers. Consider the last 90 years, in 30 year increments: 1920-1949, 1950-1979 & 1980-2009. For 1920-1949, average monthly sunspot numbers increased by around 2.5 per year, & temperatures rose at an average of 0.0095 degrees per year during that time. For 1950-1979, average monthly sunspot numbers decreased at a rate of 0.5 per year (which is almost nothing at all), and temperatures rose at around 0.0016 degrees per year (which is also almost nothing at all). For 1980-2009, sunspot numbers declined an average of 2.7 per year, yet temperatures during that period rose by 0.016 degrees per year. So we are in fact seeing the fastest 30-year rise in global temperatures, this century, at a time when we're also seeing the most rapid 30-year decline in sunspot numbers this century. I can't see how that fits with an "its the sun" theory. One final point, though not statistically significant, temperatures rose by 0.012 degrees per year between 2000 & 2009, yet average sunspot numbers fell by around 14.5 per year.
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33. CBDunkerson at 23:42 PM on 16 February, 2010
    I just noticed something odd about the OHC chart. A frequently raised topic in AGW discussions is 'natural variability', particularly as it relates to cycles of oceanic heat transfer. The 'pacific decadal oscillation' (PDO) seems to be a particular favorite. Basically, the theory is that cyclical circulation of colder deep ocean water and warmer surface waters has a strong impact on climate. So, if the PDO, as one of the larger cycles observed, is pushing alot of cold water to the surface that is going to have a cooling effect on the atmosphere. Such is often used to explain cooling trends from 1880-1910 and 1940-1970. Then the cycle reverses and ocean heat is transferred to the atmosphere, causing warming. However, looking at the OHC graph it seems like there was a drop from 1960-1970... the same time the ocean was supposedly 'sucking up heat' from the atmosphere. Then from 1970-2000, when the ocean was supposed to be releasing heat into the atmosphere, OHC went through the roof. Does this disprove oceanic heat transfer as a major driver of climate? I suppose greenhouse warming could have overwhelmed ocean cooling from 1970-2000, but why did ocean heat decline from 1960-1970? Was there a solar decline in that timeframe which would explain both the atmospheric and oceanic heat declines?
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34. John Russell at 23:58 PM on 16 February, 2010
    Ricardo @31 I think you missed the point of '40 Shades of Green's' question. He's (she's?)asking if someone with the required knowledge has done the statistical analysis on the actual data, and what the result was? A fair question I would say. As a lay response I would say there's no magic level of data that must reveal a trend hidden in noise. Imagine looking at a newspaper photograph at a high level of magnification under a microscope: with a few dozen dots (data) visible you wouldn't have a clue what the picture was about. Now reduce the magnification. At a certain point -- and number of dots (data) -- one can start to make out the image and have a stab at what's being revealed. The lower the magnification, the more dots (data) and the more certain you can be of what you're looking at. I hope that helps.
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35. CBDunkerson at 00:12 AM on 17 February, 2010
    John/40 Shades, without doing the full statistical analysis we can still use past variability as a general guide. For instance, there was a 30 year 'pause' of mild cooling in the warming trend from ~1940-1970. Thus, the current 15 year period of only mild warming doesn't seem particularly anomalous. For me, it'd have to run more than 30 years (say 40) without warming passing 95% certainty to 'give pause'. That hasn't happened before in the instrumental record so it would indicate something 'new'. Anything shorter than that is just consistent with past variations.
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36. Tom Dayton at 00:38 AM on 17 February, 2010
    Regarding the amount of time needed to detect the warming signal against the noise: The statistician Tamino addressed that explicitly in his post How Long?. (That's the same post that Steve L linked to earlier.)
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37. barry1487 at 01:15 AM on 17 February, 2010
    Here's the full text of the Easterling/Wehner paper cited by DIkran Marsupial@24 for JonMoseley@3. DIkran's description:

    "Furthermore, the observed results are in conflict with the predictions of the computer models. Therefore, the computer models are wrong." Actually that is not correct either, see the paper by Easterling and Wehner, which shows that the internal variability of the climate means that there will be occasional decadal trends showing no warming or even cooling, and that these are seen in the output of the models.

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38. barry1487 at 01:16 AM on 17 February, 2010
    Oops, forgot to include the link. http://sciences.blogs.liberation.fr/files/dix-ans-de-froid-dans-un-si%C3%A8cle-chaud.pdf
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39. oracle2world at 01:36 AM on 17 February, 2010
    Insofar as you can fit something into a headline, the text "there has been no global warming since 1995" is accurate. Now you can delve into the weeds about significance levels, time periods, datasets, overall trends, caveats, blah, blah, blah ... but the text speaks for itself: BBC: Do you agree that from 1995 to the present there has been no statistically-significant global warming Phil Jones: Yes Now if you want to start adding caveats to ALL global warming headlines ... that would be fine. Like the IPCC in its 2007 report said: "Eleven of the last 12 years rank among the 12 hottest years on record (since 1850, when sufficient worldwide temperature measurements began)." That last parenthetical statement seems to go by the wayside a lot. And maybe a mention of the Medieval Warm Period, and the Holocene maximum would be helpful. And satellite temps versus ground records that omit quite a bit of the earth's surface. Somehow the IPCC infactuation with 12 years of data was important and significant ... but the same years found to be not statistically significant don't really mean much of anything now. Any questions?
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40. Arkadiusz Semczyszak at 01:39 AM on 17 February, 2010
    Marcus "One final point, though not statistically significant, temperatures rose by 0.012 degrees per year between 2000 & 2009, yet average sunspot numbers fell by around 14.5 per year." O.K. Cyclical changes in solar activity do not (simple) coincide with the cycle of the Millennium. Agreed. But now we have a typical growth phase temperature in the Millennium cycles in a typical (for him) periods. It was not me saying that this cycle in some way depends on solar activity, and Rahmstorf. In many, many works and commentaries.
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41. John Russell at 02:31 AM on 17 February, 2010
    Oracle2world @41 What you're confirming is that Phil Jones is a straightforward, uncomplicated (and perhaps politically-naive) scientist, rather than a politician with a lawyer's brain. Given that it's agreed by the vast majority of scientists that the world has been on a warming trend since temperature recording began, would it not be totally illogical for Phil Jones to mean, "there has been no warming since 1995"? Clearly, if he thought like a politician, he should NOT have said, 'Yes'; but should have said something like, "It has not been possible to separate a trend from the noise over that period". Surely logic suggests that we must assume that the long term trend continues, given that the noise over the last fifteen years has obscured any statistically-meaningful variation from that temperature trend, either higher or lower?
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42. suibhne at 02:58 AM on 17 February, 2010
    Surely one of the most alarming part of the interview was when he(Phil Jones) indicated that he is not very good at keeping records. If one of my students said he had collected some temperature readings but the location of the the readings was uncertain then I would have to disregard them. It should now be obvious that the disputed Chinese readings have to be disregarded.
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43. Tom Dayton at 03:05 AM on 17 February, 2010
    suibhne, regarding the "disputed Chinese readings," Phil Jones and colleagues have posted a response.
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44. Jeff Freymueller at 03:15 AM on 17 February, 2010
    #41, oracle2world. Just one question. First, read post #21. If the warming trend from 1995-2009 is not staistically significant, but the trend from 1994-2009 IS statistically significant, as is the trend from any year prior to 1995 through 2009, what do you think the headline should be? #43, John Russell, I got a similar impression of Jones from the transcript. He was spin-free. Certainly it would have been better for him to have said, "the trend from 1995-2009 is not significant, but the trend from X-2009 is. The reason for the difference is that 1995-2009 is too short a time span." But we were not the ones sitting there in front of the TV cameras -- it's easy to second-guess.
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45. angusmac at 03:40 AM on 17 February, 2010
    Is it possible to post a chart on this site? I have an intersting graph based on current GISS data and a paper by Hansen et al, 2006, which I would like to post. This shows that we are currently tracking below the zero-emissions trajectory for global warming.
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46. suibhne at 03:51 AM on 17 February, 2010
    Tom Dayton I Hope that you understand why I remain sceptical about the disputed Chinese readings. No doubt the issue will be examined by each of the two inquiries.
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47. MarkR at 04:14 AM on 17 February, 2010
    oracle2world: Is it accurate? 'There has been no warming since 1995' is a very different statement from 'there has been no statistically significant warming since 1995'. In Jones' set there is a warming trend, and every year after 2001 has been warmer than 1995. There has been warming. It is not statistically significant because a certain combination of known noise could recreate that trend in 5%+ of cases. Of course, if you think my stats understanding is wrong, point me to where I can read up and fix it.
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48. suibhne at 04:25 AM on 17 February, 2010
    Phil Jones may rewrite part of 1990 report. Nature online 16/2/2010
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49. Steve L at 04:34 AM on 17 February, 2010
    angusmac @47, see the comments policy for how to post figures. Hopefully you can relate your graph to the discussion.
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50. Tom Dayton at 04:41 AM on 17 February, 2010
    But suibhne, the 2008 paper affirmed the conclusions of the 1990 paper, while lacking the possible flaws of the 1990 paper.
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