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Phil Jones - Warming Since 1995 is now Statistically Significant

Posted on 14 June 2011 by dana1981

As all Skeptical Science readers are undoubtedly aware, in February of 2010, Phil Jones was asked some loaded questions in an interview with the BBC.  Several of the questions were gathered from "climate sceptics", and Jones' answer to the second one has been widely re-published and distorted:

"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."

Why choose 1995 as the starting point in this question?  Well, that is the closest year for which the answer to this loaded question is "yes".  From 1994 to 2009, the warming trend in the HadCRUT dataset was statistically significant at the 95% confidence level (CL).  It's also worth noting that there's nothing magical about the 95% CL - it's simply the most commonly-used interval in scientific research, but it's also true that the HadCRUT 1995-2009 trend was statistically significant at a 93% confidence level. 

In other words, using Jones' data, we could say with 93% confidence that the planet had warmed since 1995.  Nevertheless, this did not stop numerous mainstream media outlets like Fox News claiming that Phil Jones had said global warming since 1995 was "insignificant" - a grossly incorrect misrepresentation of his actual statements.  The Daily Mail warped the truth even further, claiming Jones had said there was no global warming since 1995.  These media outlets turned 93% confidence of warming into "no warming". 

Furthermore, the HadCRUT dataset excludes portions of the Arctic where there are no temperature stations.  The Arctic also happens to be the fastest-warming part of the planet.  NASA's GISTemp, whose data analysis extrapolates for the Arctic temperatures using the nearest temperature stations, did find a statistically significant warming trend at the 95% CL from 1995 to 2009.  So not only are the "skeptics" cherrypicking the start date, they're also cherrypicking a dataset which doesn't cover the whole planet.

Deep Climate has detailed the history of the 1995 cherrypicked starting point.  It appears to have originated with an email from Richard Lindzen to Anthony Watts, which was subsequently published in a post on WattsUpWithThat (WUWT):

Look at the attached.  There has been no warming since 1997 and no statistically significant warming since 1995.  Why bother with the arguments about an El Nino anomaly in 1998?  (Incidentally, the red fuzz represents the error ‘bars’.)

Best wishes,


Luboš Motl made a similar argument in December 2009 using UAH satellite data, which was also published on WUWT.  Two months later, the question was posed to Phil Jones in the BBC interview, which suggests strongly that it originated from Motl, Lindzen, and/or Watts.  Regardless of the source, what really matters is that the question was based on a cherrypicked starting date, and on a somewhat arbitrary statistical confidence level, and that the media subsequently distorted Jones' response.

In January 2009, Tamino at Open Mind analyzed the data after removing the influence of exogenous factors like El Niño, volcanic eruptions, and solar variation from the temperature data.  Tamino concluded that "until 2001 the warming is statistically significant" (Figure 1).

tamino analysis

Figure 1: HadCRUT3v estimated warming rates from the plotted date to Present with 2-sigma error bars, using exogenous factor-compensated temperature data (Open Mind)

Another year has passed since the original BBC interview, and in a new BBC article, Jones notes that the HadCRUT warming trend since 1995 is now statistically significant.

"Basically what's changed is one more year [of data]. That period 1995-2009 was just 15 years - and because of the uncertainty in estimating trends over short periods, an extra year has made that trend significant at the 95% level which is the traditional threshold that statisticians have used for many years.

"It just shows the difficulty of achieving significance with a short time series, and that's why longer series - 20 or 30 years - would be a much better way of estimating trends and getting significance on a consistent basis."

As Jones notes, and as scientists like Lindzen and Motl should very well know, trying to assess trends in the noisy global temperature data over periods as short as 10-15 years is pointless.  There's just too much short-term noise, which if you're going to look at such short-term data, you at least need to attempt to filter out first, as Tamino did.

So to sum up, a cherrypicked starting date chosen by a couple of "skeptics" (Lindzen and Motl) and published by a "skeptic" blog (WUWT) was picked up and passed along in the form of a loaded question to Phil Jones in the BBC interview.  Phil Jones' answer was subsequently (and predictably) grossly distorted by various media outlets, who turned 93% confidence of global warming into "no global warming". 

In reality, the HadCRUT warming trend since 1995 was statistically significant above the 90% CL, the GISTemp warming trend (which does not exclude the Arctic) was significant at the 95% CL, and by removing short-term effects, even HadCRUT has been significant at the 95% CL since 2000.  One year later, we can now say that the HadCRUT warming trend since 1995 is statistically significant at the 95% CL, even including the exogenous factors.

Unfortunately, the main consequence of this sequence of events was that much of the public was misinformed by media articles claiming that global warming since 1995 was "insignificant" or non-existent, which are both factually incorrect statements.  Misleading the public may well have been the goal of those individuals who originally cherrypicked the 1995 starting date and the HadCRUT dataset, and if so, they succeeded.  And not surprisingly, Anthony Watts continues to mislead his readers, claiming Phil Jones' comments are "an about face...From the “make up your mind” department", when in reality Jones' comments have been consistent and accurate throughout.

This reactions to this story have revealed a number of media outlets whose aim is not to accurately inform their readers with regards to the climate, but rather to misinform them.

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Comments 151 to 181 out of 181:

  1. Thanks, Dikran.
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    Moderator Response: [Dikran Marsupial] No problem, lets see if it has any success!
  2. Dikran, Many thanks for all your incredibly informative posts here.
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  3. #144 Dikran "Yes, fine, the data are autocorrellated and an OLS trend is an optimistic calculation." The head article says "One year later, we can now say that the HadCRUT warming trend since 1995 is statistically significant at the 95% CL, even including the exogenous factors." Is the statement in the head article correct?
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  4. Charlie A Yes, I expect it is, in the sense that the slope of the OLS trend is statistically significant. There may be other, perhaps better, tests of statistical significance where perhaps it isn't. There is scope for arguing that the headline is wrong, but if you are going to be as critical of Jones as you possibly can, you need to ask yourself why you are not being even more critical of Linzen and Motl, whos errors have been far more egregious. The point is that statistical tests over such a short time scale have little statistical power, and hence the probability of a false-negative (not being able to reject the null hypothesis when it is false) is high, so it doesn't mean much if the slope is not significant (even without the cherry picking). It is also worth noting that Prof. Jones is not making a big deal out of the trend going from insignificant to significant. He is still saying that longer timescale trends (e.g. 30 years) are what we need to look at.
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  5. Henry@TomCurtis The average temperatures for the daily mean, maxima and minima and other weather data for Brisbane are given at the end of each month of the year from 1976 to 2011 at this site: For the record and for those interested: As it stands at the moment (on my pool table), it appears that maxima, means and minima have risen in a ratio of about 4:2:1 over the past 4 decades. For the time being, my conclusion is therefore that the warming is natural because it is the maxima that pushed up the average temps and minima. I think if I could get these results, anyone else should be able to get the same, as long as they play the game according to the rules: i.e. 1) randomly 2) balanced, ::::NH versus SH Namely the funny thing is that I observed now is that the warming is not at all the same in the SH (where I started playing) and the NH. Why that is I don’t know> perhaps it could be because there is much less landmass in the SH? But why would that make a difference? Anyway, whatever the reasons, I now have to carefully look at my table again, to balance it, i.e the same amount of stations NH and SH + approx. same NH latitudes and SH latitudes. Not an easy task for one and only person….with only a limited amount of hobby time and that is: yours truthfully Henry Henry@Dikran I don't need a comment from you.
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    [DB] "Henry@Dikran
    I don't need a comment from you."

    If you do not wish others to respond to comments you post here then don't post here.  Either way, try to exercise more civility.  Politeness goes a long way towards establishing credibility.

  6. Henry@Dikran "I don't need a comment from you." s/need/want/ If you can't take on board constructive criticism, your analysis will continue to be meaningless. Not engaging with technical criticism of ones scientific position is denialism. Your perogative of course.
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  7. How about: "Of course yes! What would you except from so short period? We use much longer time frames -- 30 years or so -- to be sure a trend we see is real. Still... Even the warming we've witnessed during the last 15 years only, it is almost there. Only haircut, two or three percentage points, short from being statistically significant."
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  8. Henry@Dikran & moderators You will remember that Dikran thought that my scientific method is rediculous...I have replied to that accusation and I have not received an apology from him. So what would be the point in further engaging with him? Anyway, you now also stated that I cherry picked my stations. I did nothing of the sort. Why would I lie or cherry pick? To fool myself? My honesty and honorability speaks for itself. This is just a hobby of mine and I just thought I would help you by letting you have a look at what I found on my table. there is no global warming due to an increase in GHG's. Just get that ....
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    Moderator Response: (DB) We do indeed get that you somehow feel extrapolating non-official regional data via questionable statistical methodology and using that to hand-wave away net warming measured globally during a time of flat forcings (other than the rapidly rising levels of CO2). Yes, we get that. You are very mistaken, however.
  9. MoreCarbonOK I have only made a brief review of this thread, but I think you will find that I said your analysis was "statistically nonsense" (i.e. from a statistical point of view it made no sense). It was you that transposed that into "ridiculous" in this post, AFAICS I said no such thing. I could be wrong of course, but if not, perhaps you should apologise for your calumny? ;o) I also said your approach was a recipe for cherry picking (whether deliberate or inadvertant), not that you had cherry picked. If you pick sites at random and get a result that suits your argument, but don't test that your result is robust to that random selection, how do you know you did not inadvertantly cherry pick (you can't). The point in engaging in discusion with me on the defficiencies of your statistical methodologu is exactly the point in scientists engaging with the criticism they recieve of their papers from the reviewers. Generally it improves the standard of their work. I certainly take that view of the referees reviews of my work and I don't take it personally or refuse to listen to them. If I disagree, I explain why. If I can't convincingly explain why, that would be a good indicator that they were right and I was wrong. P.S. I expect the moderators will delete your post and my reply as they are both off-topic, but do read the last paragraph, it is sound advice.
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  10. Dikran says:The point in engaging in discusion with me on the defficiencies of your statistical methodologu Henry says: Which are? Why don't you show me which specific value(s) in my table is incorrect? I will be happy to send you the complete Excel file that made up that one figure on my table. (-Snip-) I will be visiting another station in the SH soon again. (-Snip-)
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    Moderator Response: (DB) Inflammatory snipped.You are welcome to discuss climate science in this forum but spare us the inflammatory rhetoric and tone.
  11. MoreCarbonOK If you compute statistics correctly using an inappropriate methodology, the results are still meaningless. I have already explained why your methodology is wrong, looking at individual stations rather than regional averages is the first issue. Glen Tamblyn has written an excellent series of article explaining why climatologists don't look for trends for individual stations, and explains how regional and global averages are calculated. That would be an excellent place for you to start. The first post is here.
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  12. MoreCarbonOK @155, as I explained previously, the site you rely on is not an official site, and has inaccurate data. As you seem to think the monthly averages will be ok even if the daily values are inaccurate, I have checked the monthly mean for May 2011 for you. Record: Tutiempo | BoM Max Temp: 22.4 | 22.4 Min Temp: 11.2 | 12.0 Humidity: 70 | 65 Once again, Tutiempo does not accurately record the official values. So, while it is very good of you to try and demonstrate that Tutiempo's copying errors generate specious trends in the temperature data, I fail to see how that has any relevance to global warming. It's very interesting that you think you can refute temperature trends independently calculated by four different team from surface data, with one of the teams funded by and sympathetic to deniers by using error strewn data and dodgy statistics for just five stations. It is also interesting that you can refute four different calculations of temperature trends from satellite data, one of them from a team of well known deniers. But it is interesting only in what it tells us about you, for it tells us nothing about climate science.
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  13. Henry@Tom Who says BoM is the correct one and mine is wrong?
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    [DB] See here.  Tu Tiempo does not specify a source for its info.

  14. MoreCarbonOK says... "there is no global warming due to an increase in GHG's. Just get that...." I think you need to take a step back from the subject for a moment and evaluate what you are trying to claim. I come across similar statements to this repeatedly when discussing AGW online. If there were any validity whatsoever to this claim it would be nothing short of revolutionary. It would be tantamount to overturning the theory of evolution. No disrespect intended here but the idea that a "hobbyist" has uncovered something elemental that the rest of the "professional" science community has missed is far fetched to say the least. Not that it isn't possible, just very far fetched. I believe what people here are trying to point out to you is that there are very serious errors in your analysis. No one is suggesting that you shouldn't pursue this hobby but expect to take heavy fire from the people who genuinely understand the full details of the subject matter.
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  15. 164, Rob, As an interesting aside, I'd actually be ready to argue against your statement that a hobbyist overturning the professional community in science (any arena of science) is possible. It was, once. When Einstein did his thing, the world was younger, less populated, and I'd argue that the sciences were at a simpler level that was on the cusp of being inaccessible (from a "leap forward" sense) to the common man. Einstein may well be the last "hobbyist" genius the world ever sees. And mind you, he still earned a PhD in his field in 1905, the same year he proved his genius by publishing four ground-breaking papers. By 1908, he was considered a leader in (and part of) the field, so the fact that he worked in a patent office and did his most important research in his spare time makes him a hobbyist-genius, but only just barely so. No, I think all of science has moved on to the point (in both body of knowledge, expense of time and equipment, and other avenues) where the days of an Edison or a Franklin are simply gone. Today man has evolved into a hive-mind social creature, like bees on steroids. There is simply too much knowledge there, with too much detail, for any one person to master and surpass it and to surprise everyone, even in just a single focal area of a single field. It's not that there isn't a lot of room for ingenuity, and that spark of genius, but in order to present such a spark, someone is going to have to dedicate their life to a field, starting with hard study and education, and followed by years and years of effort and climbing the rungs of the ladder. The idea of the hobbyist dilettante genius is, today, just one more weak plot left over for Hollywood movies.
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  16. Indeed, Rob, it sounds like Henry is saying, "Yah, I made this spreadsheet, and I made this graph, and therefore there is no AGW." Henry, the best way into this sort of project is to take a thorough look at the existing literature. You're going to have to do that anyway if you're going to publish your results (and you'll want to do this if you think the results of your study are in any way important, which you apparently do). Find out how others have measured SH land surface temps. Start your project off by telling us why these other analyses aren't telling the whole story, and why your project will help tell a more complete story. And if you can do that, and if your math and methodology (why did you choose the stations you did and not others?) check out with your peers, then you can discuss the results confidently. However, if you're going to extrapolate to the conclusion that AGW is not happening from the basis of one small SH surface station analysis, you'd better prepare for, as Rob says, "heavy fire." The chain of logic you'd have to construct would need solid links that overturn established radiative physics, observed anomalous warming in other parts of the globe, observed anomalous sea level rise, thousands of paleo studies, etc. etc. etc. Right now, you're missing a few links.
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  17. Sphaerica... I totally agree. I seem to remember there were some points in very early astronomy where people who were essentially hobbyists made very important contributions to science (but back then, virtually every astronomer was a hobbyist). Overall, I'm trying to be kind and open minded about it. The possibility is so remote that it's hard to even imagine it happening this day in age. IMHO Henry isn't just playing long, very very long odds, he's playing the lottery without buying a ticket... hoping he'll get the winning ticket by walking the streets, finding it laying on the ground. So, yes, you could, technically, win the lottery that way... But I hear you. Those odds are functionally zero.
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  18. If you go back to a comment I made yesterday regarding Henry's website, what he's essentially done is googled up all the other climate change denial sites and cobbled together his own version of the same wrong information, while adding a dash of his own "research." I see this exactly same thing time and time again out there. It's this self perpetuating, self referencing, unsupportable mis-information propagating on the internet. And it's not like I even question that people like Henry genuinely believe what they are posting. That's human nature. We want to prove what we want to believe. But that's not science. Science is coming to the truth in spite of what we want to believe.
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  19. 169, Rob, What bothers me is that he's using SkS to try to promote his... stuff. Note that he never, ever fails to make a comment without including a link to his site, and "stuff." Although in his case, I think it would do more reasonable people a lot of good to look at it, and realize what a tangled web a Galilean spider (well known in the arachnid community for it's ability to drop large objects from great heights, and yet race down faster than they fall, to catch them at the bottom) can weave.
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  20. MoreCarbonOK, the Bureau of Meteorology is Australia's official meteorological organisation. As such it operates directly a large number of meteorological stations throughout Australia, including the Brisbane Aero site (Brisbane airport). As such they are the initial source of any data from Brisbane Aero. There data is picked up and republished on the web by a large number of weather sites, some of whom acknowledge the BoM, and some of whom do not. Those that do not, including Tutiempo, may well have copied their data from secondary sources. Some of those sources may have deliberately introduced errors as a method of copyright protection, or, of course may have just inadvertently introduced errors.
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  21. sphaerica I shouldn't worry, the attitude to constructive criticism he has displayed here means it probably hasn't been much of an advertisement. His credibility is rather lower now than when he made his first post here; but it was his choice to behave in the rather unscientific way he did.
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  22. MoreCarbonOK I am not going to moderate your post as I am taking an active part in the discussion, but your post contains an accusation of dishonesty, which is explicitly forbidden by the comments policy. If you don't want your posts deleted by the moderators, please conform to the comments policy. BTW, your post only reduces your credibility further as yet again you are demonstrating a complete lack of self-skepticism. There is no good reason to think Tuitempo has the correct data and BoM data is incorrect. There will be a lot of organisations that downloaded the data from BoM at the same time or before Tuitempo, so if BoM were fiddling the data there would be no way they could get away with it. The guys at BoM are not stupid and wouldn't try fiddiling with data when there was no chance of getting away with it, even if there were something to gain from it (which there isn't, the data are primarily collected for weather forecasting, not climate studies, so they would be funded to collect it anyway).
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  23. MoreCarbonOK @172, having had experience with deniers I expected an accusation of dishonesty against BoM as soon as the data discrepancy was shown. It was for that reason I chose to compare the most recent full month, when the record was most easily checked, and hence for which any "fiddling" with the data. Despite that, you did not disappoint, and made the accusation anyway. Your accusation is, of course, absurd as is the supposed motive. As if their could not be sufficient commercial demand for a weather record at the airport of the capital of Queensland so that BoM needs to fiddle the data. Please note that you have made the accusation based on no evidence beyond the fact that BoM data was inconvenient to you. Further, you have made absolutely no checks on your hypothesis to see if it had any validity. That clearly shows that whatever your hobby is, it is not science. As it is, it is very easy to check if BoM has altered the data by comparing it with other records of the Brisbane Airport data. The first alternate record I could find was Weatherzone. Performing the same checks as I did for Tutieme (first four days and monthly mean for May 2011) I found complete agreement with BoM data. (I could not check humidity as it is not recorded at Weatherzone.) Please note the logic here. If BoM modified the data before initially issuing it, Tutiemo would have the modified data, and hence the modification could not be the explanation of the discrepancy between tutiemo and BoM. If BoM modified the data after first issuing it, then Weatherzone, who keeps a daily record, would have the unmodified data and would not agree with BoM. Hence this is simply a case of tutiemo getting the data wrong. I request that the moderator leave your post, even though it clearly violates the comments policy, and the replies on this thread. In that way your intellectual integrity will be clearly advertised to anyone tempted to take your website seriously.
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  24. You guys are obviously not interested in following the logic of my thinking and investigations as it progressed and still progresses so what is the point in arguing if you cut everything I say right left and centre. Carry on and stay in your ignorance.
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  25. MoreCarbonOK So to summarise: All of the professional scientists at NOAA, NASA GISS, UK Met Office, CRU, RSS, UAH (who have relevant qualifications and have studied the data in depth) are wrong and you (who apparently does science as a hobby) are right. If there is a discrepancy in the data, it is at BoM (who collect and distribute the data) not at one of their clients. You apparently have nothing to learn from us (as you have not engaged with any of the constructive criticism so far), but we (in our ignorance) have everything to learn from you. Do you realise how you come across? Do you think anyone will take your analysis seriously having seen your display of hubris here? Most physics departments from time to time have a member of public come along with a proof that Einstein was wrong, or a prototype for a perpetual motion machine, or maths department have someone claim to have a short proof for Fermat's last theorem, or a proof that Godel was wrong etc. You are heading into that territory, please do yourself a favour, doing science as a hobby is something very admirable, but you do need to learn the basics first, and have some humility.
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  26. MoreCarbonOK... There is an old saying. "If you can't stand the heat..." To be quite honest, these guys are not pushing very hard on you. They're only subjecting you to the very lightest of skepticism that every scientist gets put to when publishing work. If you want to do science as a hobby then you should at least accept some of the pressure that any scientist would expect as routine in their research. Brandishing claims of corruption just doesn't cut it. It's a rather un-skeptical cop out.
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  27. 165 I would call a man with PhD in his field some frantic hobbyist :) Einstein might has been outsider of the scientific community, but he was very aware of the works of others. He himself stressed intuition, logics and 'inner view'. But the real ground breaking thing, General Relativity (1916) is based on some very serious (and tedious) mathematics. It is also a work of some strange and ultimately genius person, with extraordinary inner view... Maybe one could do great things as hobbyist. But at least you should learn the language professionals use, so you work could be criticized. If your day job is in McDonalds' is rather irrelevant.
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  28. I have one quite close person, who is intelligent and in many ways open minded. And despise of his lack in education his understanding of scientific matters is well beyond layman. Still he insists, he can trisect an angle with a compass and a straightedge. He is in complete denial about mathematics, which show you can't do it. Neither can he produce any viable proof of the process for scrutiny. It's all about "the conspiracy of the high educated".
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  29. 178, jatufin, In the misquoted words of Darth Vader, as he tried to line up young Luke Skywalker in his sights and save the Death Star from total destruction:
    The Dunning-Kruger is strong in this one!
    And then he blew poor Skywalker's x-wing fighter to little bits, and the Empire ruled the galaxy for the next 1,000 years.
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  30. The article says, "This reactions to this story have revealed a number of media outlets whose aim is not to accurately inform their readers with regards to the climate, but rather to misinform them." But is this a surprise to anyone? It should not be. The press has been abusing freedom of speech this way for many decades now. It has only become worse with greater and greater consolidation of corporate ownership of the press (Murdoch being only one unsavory example). If there is anyone to look back on what went wrong 300 years from now, they might well say that this failure proves that the exalted democratic principles of "freedom of speech" and "freedom of the press" were the cause of global warming -- and the downfall of a lot more than just democracy.
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  31. I think it might be a good idea to update the Did Phil Jones really say global warming ended in 1995? article with the 2010 story.
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