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Climate Hustle

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,

Dick

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 51 to 100 out of 181:

  1. 48. if a 0.12 trend over 15 years is not statistically significant, then a -0.0281 trend over 10 years certainly isn't.

    For the record, I didn't question whether or not the trend was significant ( Though Lucia has concluded it is not and offers up the source code of her analysis ).

    My point was that the rate is fairly low.

    We shall know in the fullness of time ( hence my nonsensical moniker ).
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    Response:

    [DB] "For the record, I didn't question whether or not the trend was significant"

    On the contrary, yes you did.

  2. "way too much attention is placed on the single metric of average annual global mean temperature of the troposphere" - yes, why oh why is no attention being paid to increased frequency of catastrophic events; changes in species distribution and breeding seasons; ocean acidity; more and more record high temps; melting glaciers and ice caps - how silly those old climate scientists are.
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  3. Here are the decade numbers from my previous comment; #19.

    1970s: -0.074
    1980s: 0.098 (+0.172)
    1990s: 0.242 (+0.143)
    2000s: 0.430 (+0.189)

    CW, your claim that there is a cooling trend since 2001 is a sham based on selective data extraction in order to affirm a preconceived notion, aka "cherry picking".
    Rational Wiki: cherry picking

    Cooling trend to 2010:
    2001, 2005

    Warming trend to 2010:
    1850-2000, 2002-2004, 2006-2009
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  4. Scratch that last bit. It's been a long day, and my eyes crossed when I looked at the data.

    How is there a cooling trend from 2001, when 2001 was cooler than 2010? The only 2 years warmer than 2010 were 1998 & 2005.
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    Response:

    [DB] Per CRU, "The years 2003, 2005 and 2010 are only distinguishable in the third decimal place."

  5. @21 Albatross

    "Ironic beyond belief, because the CRU employs the same group of scientists who the 'skeptics' accused of fudging"

    Not only that, but UAH is home to two of their favorite skeptic scientists, Christy and Spencer.

    Priceless. double irony?
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  6. This is priceless, in a incredibly desperate move to try continue the deception and confusion, a 'skeptic' blogger has now feigned ignorance and claimed that the warming in the HadCRUT data since 1995 and 2010 is not statistically significant at the 95% confidence level because they could not figure out which data Jones is using.

    Well, it would help if they used the same data that Jones used (and that I used below). Of course, uncritical 'skeptics' have bought their deception hook line and sinker.

    Here is the output from a professional statistics package. Note the bolded p-value of 0.042 is less than 0.05,that means that that the warming trend in the variance adjusted HadCRUT data is indeed statistically significant at the 95% confidence level.

    Regression Analysis: HadCRUT3 (1995-2010) versus Year

    The regression equation is
    HadCRUT3 (1995-2010) = 0.293 + 0.0109 Year

    Predictor Coef SE Coef T P
    Constant 0.29328 0.04685 6.26 0.000
    Year 0.010865 0.004845 2.24 0.042


    S = 0.0893442 R-Sq = 26.4% R-Sq(adj) = 21.2%


    Analysis of Variance

    Source DF SS MS F P
    Regression 1 0.040134 0.040134 5.03 0.042
    Residual Error 14 0.111754 0.007982
    Total 15 0.151888

    Unusual Observations

    HadCRUT3
    Obs Year (1995-2010) Fit SE Fit Residual St Resid
    2 2.0 0.1390 0.3150 0.0386 -0.1760 -2.18R
    4 4.0 0.5290 0.3367 0.0312 0.1923 2.30R


    To be fair the "skeptic" does state that "I don’t think this lack of significance has great scientific importance..."

    Exactly, this whole cherry-picking exercise is moot, and I am getting tired of playing whack-a-mole.
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  7. Albatross:

    Is that an ordinary least squares calculation? If so, caution is required. OLS isn't generally applicable to time-series data because of the correlations. IIUC the slope should be OK but the uncertainty will be underestimated. You need general least squares, and feed it some estimate of the covariance matrix (banded diagonal based on autocorrelation will probably do - or maybe detrend first - I'm out of my depth).

    If this is a GLS calculation, then you're way ahead of me, but hopefully this warning will be useful to others!
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  8. Philippe Chantreau

    sadly this is nothing new

    I learned long ago, never to wrestle with a pig. You get dirty, and besides, the pig likes it.George Bernard Shaw

    With the approach Jones took, he made the point to those willing to listen and he stayed clean.
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  9. CLimateWatcher

    Your post merely demonstrates that you don't know what a null hypothesis is.

    Secondly if the observed trends are within the stated uncertainty of the projections, that means that the projections are as accurate as they claimed to be.
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  10. Dikran writes: "With the approach Jones took, he made the point to those willing to listen and he stayed clean."

    Yes, but when it comes to climate change, the rest of us need the experts to make the point in a 'clean way' to those not willing to listen, too.

    What you say Dikran, is a bit like the chap who steps out onto a pedestrian crossing and then when he's run down says, "but it was my right of way!". No point in being screwed over while being right; better to avoid being screwed over in the first place. The trick is use a bit of pragmatism and use language cleverly while remaining honest. That's something that comes easier to some people than to others -- but with practice most people can get a lot better at it. My point is that it's quite possible to phrase an honest answer in a way that makes it difficult to be twisted.

    And to Badgersouth, who suggested this critiquing of Jones' interview on a public comment thread to be 'unseemly and unwise'; I think you misunderstand. This is not about blaming Phil Jones -- it's about learning from events and improving the way climate change is explained to the general public in the face of a dishonest opposition. I'm quite confident Phil Jones would agree.
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  11. Kevin C @57,

    A valid point, I think, but when one is deliberately cherry picking.....I think that is really the crux of this matter and the role in this fiasco of Lindzen in knowingly acting to deceive and/or confuse.

    To answer your question I used exactly the same data and technique (OLS) that Jones did to be faithful to his statements and analysis.
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  12. Until the "Climategate" scandal, I chuckled like a middle-schooler when witty, sarcastic global warming denialists on the blogs mocked "Al Bore" for being a fat, hypocritical moneybags. I didn't want to believe in the "inconvenient truth" of global warming. I was in denial. Still, I was kind of worried in the back of my mind that global warming might be true.

    "Climategate" forced me to face my denialism. I read those e-mails and the nasty and mocking commentary about them, and then I read what the scientists actually were saying in their own words.

    I think Phil Jones's infamous BBC interview shows how consciously dishonest these few denialist scientists and loud-mouthed journalists are. They knew that ordinary people wouldn't understand what statistical significance means.

    The denialists are the cherry-pickers. Once I saw that the Republican Party was spreading these (-Snip-), I became a Democrat.

    When the Republican politicians come to my door or call on the phone for my vote, I tell them that the Republicans deny climate change so I won't be voting for them any more.

    I tell them that I believe the National Academy, the Vatican's Pontifical Academy of Sciences, the CIA, the EPA, NASA, NOAA, OSHA, the Pentagon, and Al Gore.

    If I can read both sides and figure it out, the Republican politicians can too. They are just paid (-Snip-) who don't care about the truth at all.

    Climategate made me pay attention to climate change, and I learned that it's not the climate scientists who are trying to trick us.

    Al Gore is probably not a bore. He can't possibly be as boring as some of those conspiracists on Faux News like Sean Hannity and Glenn Beck. I don't believe them at all any more. Every day they repeat the same conspiracy theories over and over and over and over! It is so boring! They are so self-righteous! And there is never any news!

    Al Gore is trying to learn about climate change and share what he is learning with the rest of us. That's what leaders do. I'm sure he makes some mistakes when he tries to translate what the scientists say into layman's terms; but I don't think he is lying to me like Senator Inhofe, Joe Barton, Attorney General Cuccinelli, James Delingpole, Anthony Watts, Sean Hannity, or Glenn Beck.
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    Response:

    [DB] Thank you for taking the time to share with us.  Skeptical Science is a user forum wherein the science of climate change can be discussed from the standpoint of the science itself.  Ideology and politics get checked at the keyboard.

    Please take the time to review the Comments Policy and ensure future comments are in full compliance with it.  Thanks for your understanding and compliance in this matter.

  13. Albatross @61:

    Thanks, and also for answering my unasked question 'was Phil Jones using OLS or GLS?'!

    I need to learn R, and I guess answering the question 'does it make much difference' will be one of my early projects.
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  14. Just a rhetorical question here:

    Why do "skeptics" always choose the temperature data most compromised by "climategate" over the NOAA/NASA/RSS/UAH data to support their claim that the Earth has been cooling over the past decade?

    Like I said, a rhetorical question.
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  15. I'd just like to support (belatedly) Dikran's point about the incorrect interpretation of classical p-values as levels of belief.

    Yes the correct interpretations are hard to understand, but putting incorrect interpretations like "we could say with 93% confidence that..." does no-one any favours.
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  16. John Russell You are missing the point. There is no way to give an honest answer to that question that gives no room for misinterpretation by a dishonest adversary, and I rather doubt Prof. Jones was in a position to refuse the interview (given the circumstances). If you think such an answer exists, lets hear it.
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  17. Recall Uncertainty, noise and the art of model-data comparison.

    Is there an online updated link to 60 month and 132 month running averages of the global temperature?
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  18. Pete @67,

    Re the running averages-- not to my knowledge. If someone knows please share. Thanks :) I was planning on emailing Hansen and asking them to include that as one of their regular monthly graphics.
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  19. Pick up sticks.

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  20. Is there an online updated link to 60 month and 132 month running averages of the global temperature?


    That's what Wood for Trees is for.
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  21. @Dikran - 66:

    I suggested one possible defensive form Dr Jones' answer could have taken, back on comment 32.

    I'm not a scientist, but I'll bet there are a dozen of your colleagues on here who could produce any number of honest replies to that question that would have been much more difficult for those in denial to exploit. Maybe they would like to take that as a challenge if you like: what would have been a better, but equally honest answer from Phil Jones?

    The key point is not to start by saying you agree. That's a very simple rule when answering questions that can be considered hostile and you'll hear politicians using that technique all the time. Protecting your answer against misuse might be gamesmanship, but it's not dishonest.
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  22. Dikran Marsupial @66, with respect, Jones could have answered along the lines of:

    "The Earth has warmed by 0.12 degrees since 1995 which in global terms is certainly a significant increase, but it does not quite meet the statisticians test for statistical significance. That is more because of the short interval being considered than the size of the increase. The rise from 1994, for example, does meet the test for statistical significance. Of course, whether the rise meets a statistical test makes no difference to it impact on melting ice sheets, and increased range of tropical diseases."


    Had he done so, misrepresenting the answer would have required far more selectivity in quotation, and the misrepresentation would have been significantly more transparent to those seeing the full quote.

    On the other hand, people seeking to misrepresent an opinion will do so no matter how selective they need to be. Further, even pausing to think is not always a wise strategy. Such pauses can be, and have been left in the edit to create the impression that the interviewee is speechless, or unwilling to answer the question (as happened to Richard Dawkins on one occasion).
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  23. Going back to the original post - which includes a graph from CRU data and shows warming rate in degrees C/year - given that that number is always positive (I see the error bars drop negative, but the claimed number is positive), how can there have been a cooling trend? Wouldn't at least one year have to be below zero.

    I went and got myself confused. Clarification appreciated.
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  24. I wonder.
    I think it does not matter whether the increase in temps. is statistical significant or not.
    What is important though is whether the warming is man-made or natural.
    My conclusion is that it was natural warming. Namely, there is no proof of any heat entrapment caused by an increase in GHG’s. Except on Honolulu, maybe, but that result there seems a bit suspicious to me. In hindsight, I forgot that we have volcanic activity there. So I should not have visited that station.
    http://www.letterdash.com/HenryP/henrys-pool-table-on-global-warming

    So you can all stand on your heads now and scream at the nations to stop using fossil fuels but even if you were able to stop that now, or reverse it, it would not change the results.
    Now I will admit that some type of systematic error may be incorperated in my results but essentially we are still comparing apples with apples, assuming the equipment used all over the world to measure temps. is more or less the same.

    What is interesting to note in my results is that there has been no global warming on the SH (the first 5 stations in the tables). It all happens in the NH. Any ideas as to why that is? Anyone?
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  25. Global warming doesn't 'happen' at the local level.

    Global warming affects the whole of the global atmosphere and ocean systems.

    And because of that general, global, warming we observe and measure different events at different, specific, localities.

    Therefore we see more or less warming/ drying/ flooding/ snowing/ melting in different places and seasons. The planet's climate is not uniform in the first place. So there's no reason to expect that effects of a general change will be uniform in any particular, specified localities.
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  26. MoreCarbonOK @74

    Visited your site and eyeballed the data table. How are you calculating the C/yr each month for the various sites over the 35 years? I see a lot of your sites have wildly swinging average rates between the months! Over 35 years this would be completely implausible. You need to make sure that you are properly fitting linear trends to each data set, and not simply calculating using only the first and last values of the set (otherwise your yearly trend error range is +/- twice maximum monthly variation divided by 35 years).

    I haven't done statistical trend fitting myself, but I'm sure there is some good advice on the internet somewhere. Hopefully someone here can offer a suggestion for you.
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  27. John Russell O.K., so you don't start by agreeing. What happens if the interviewer presses for a direct answer "so the increase in temperature is not statistically significant then?". Not giving a direct answer in such situations means you end up making a fool of yourself, c.f. e.g. Paxman versus Howard. As I said, not giving a direct answer to the question would end up with the hostile media presenting it as "the question Phil Jones wouldn't answer". The last thing we want is for scientists to act like politicians (or at least to sound like them)!

    Tom Curtis Had Jones said "That is more because of the short interval being considered than the size of the increase." it would not have been an accurate/honest statement. The lack of statistical significance is due to the size of the increase, it is too small given the noise level and the size of the window.

    "Of course, whether the rise meets a statistical test makes no difference to it impact on melting ice sheets, and increased range of tropical diseases."

    would also attract criticism by those who would attribute ice melt to natural ocean cycles etc. That is probably a bogus explanation of course, but they would point out that you were basis a causal link between global warming and ice melting where the global warming was not statistically significant and hence you should not claim it exists (following normal scientific practice). Basically if it is O.K. for you to ingnore the result of tests of statistical significance, why isn't it O.K. for them?
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  28. MoreCarbonOK @74

    Perhaps average each data set's year to year difference for each month over the 35 years. That way any single unusual year gets averaged out. Unfortunately its 35 times the work you've already done, but that's the treatment the data needs to reduce your errors by a factor of 35.

    As to the wisdom of only using a tiny sample of available stations, well I hope they are at least well spaced for latitude. I'm sure you'll appreciate that the amount of greenhouse warming depends on the latitude and is strongest at the poles.
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  29. MoreCarbonOK @74, edit to my post @76

    (otherwise your yearly trend error range is +/- twice maximum monthly variation divided by 35 years)

    should be:

    (otherwise your yearly trend error range is +/- twice maximum monthly variation irrespective of the 35 years of data)
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  30. MoreCarbonOK@macoles


    I know my stats and I know my method is right.
    Just average monthly temps as recorded / versus time.
    Every month of the year at a weather station treated as a new test.
    Example: look at the results from Brisbane:
    http://www.letterdash.com/HenryP/no-global-warming-in-brisbane-australia


    Just doing the linear regression in EXCEL
    it calculates the trendlines automatically....(In the old days we had to sit with a calculator!!)
    the slope you get (temp versus time) is the average increase noted over time.

    there are no errors. This is it. It is as easy as pie. If you don't understand it how I got those results you must study Stats 104.

    I see you also don't know why the southern hemisphere shows no warming. Quite a difference
    (see 2nd table from my pool table, mean average temp.)

    No global warming as a result of an increase in green house gases, in any case.

    http://www.letterdash.com/HenryP/henrys-pool-table-on-global-warming
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  31. MoreCarbonOK wrote "Every month of the year at a weather station treated as a new test". So how do you deal with multiple hypothesis testing issues?

    BTW, you do also know that the weather noise at individual stations is very large compared with the expected trend (so for station data you would not expect to see a statistically significant trend at station level). Spatial averaging averages out the weather noise and leaves you with whatever secular variation is in the data (i.e. what we call climate rather than weather). That is why climatologists look at long term regional or supra-regional trends, not trends at individual stations.

    See Glenn Tamblyn's excellent series of articles starting with this one for more information.
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  32. 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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  33. 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.
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  34. @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
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  35. 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.
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  36. 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?
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  37. #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?
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  38. 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.
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  39. 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.
    0 0
  40. MoreCarbonOK, what do you think of this study http://www.agu.org/pubs/crossref/2005.../2005GL024379.shtml
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  41. @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?
    0 0
  42. @Eric

    From opening the link that you gave, I cannot see the (original) data & info
    only an abstract.
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  43. 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.
    0 0
  44. 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?
    0 0
  45. 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
    0 0
  46. 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.
    0 0
  47. @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.
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  48. 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.
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  49. 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 significant holes 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.
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  50. 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... :-)
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