As most will know by now, Judith Curry has started her own blog, Climate Etc. In a recent post entitled “doubt” she said some things that highly surprised me. Basically, she claims equal evidence for anthropogenic forcing and natural variability being responsible for “most of the observed increase in global average temperatures since the mid-20th century”:
As an example, my personal weights for the Italian flag are:
1. white 40% [uncertainty and unknowns]
2. green 30%, [evidence for anthropogenic forcing]
3. red 30%. [evidence against anthropogenic forcing]
Before posting this, I had an email conversation with Judith Curry about these issues (so as to minimize any misunderstanding on my part). She wrote back (reprinted with permission):
I think you are misunderstanding what the IPCC actually says. The statement says MOST (>50%) of the warming can be attributed to anthropogenic, with an confidence of very likely (>90%). My balance of 50-50 is a hair outside the IPCC range (which could include 51-49), and 1% difference is in the noise here. Most can imply 51% or 90%. I will be discussing the issue of attribution at length in a future point. But my main point in the doubt post is the size of the white area, which is bigger than 5-10% IMO.
So she would translate the IPCC statement in the Italian flag style as anywhere between
white: 10 -1
green: 46 – 89
red: 44 – 10
Her own estimate is not that far off (in terms of the ratio between green and red) from the most conservative IPCC statement (where “most” means “just a bit more than half”), except having a much greater estimate of the uncertainty (which is her main point). So she seems to interpret red and green as portions attributable to anthropogenic and natural forcing, whereas initially I had interpreted them as evidence for the statement at hand versus evidence against. Both makes sense, but both are different. Also, one could claim that the IPCC statement encapsulates the uncertainty in the fairly wide “most of the warming”, i.e. it could still span a wide range, allowing for plenty of uncertainty. Similar as say, the weather in a week’s time is very uncertain, but I can still say that it’s very likely to be in between zero and thirty degrees C (being late september in Holland). These different interpretations make me doubt the usefulness of the Italian flag symbol to aid in clarifying (dis-)agreements.
Judith also claims equal evidence / equal portions of attribution for her “litmus test question”:
Will the climate of the 21st century will be dominated by anthropogenic warming (green) or natural variability (solar, volcanoes, natural internal oscillations)?
which is the question with the greatest policy relevance, IMO. My scores on this one are
green 25%
white 50%,
red 25%.
This is astounding. I interpret this as claiming equal evidence pointing to natural variability being dominant over the next 90 years as compared to anthropogenic forcing. Or alternatively, an equal portion of 21st century climate change being attributable to human induced warming as to natural variability.
I’ve read quite a few “skeptical” papers that attempt to blame the warming on natural processes, and even if you’d take them as face value (even though in most cases they haven’t stood up to scrutiny), their collective body of evidence is a molehill compared to the mountain of evidence pointing to the dominance of anthropogenic forcing.
In a comment, Judith points to a blog post at Skeptical Science, with graphs of several natural forcings (solar) and cycles (PDO, ENSO) for the past 25-30 years. They exerted a slight cooling effect over this period. In contrast, CO2 exerted a strong warming effect, and indeed, the temperature has gone up. That hardly qualifies as equal amounts of evidence pointing to the warming being natural versus anthropogenic.
For future warming, her pronouncement is even stranger. In all plausible scenario’s, greenhouse gas concentrations will continue to rise for at least another few decades; in a business as usual scenario for many more to come. What natural forcing or variability could plausibly rival this relentlessly rising anthropogenic forcing in magnitude? Is there evidence at all for that being plausible? If so, is that evidence really as large as the evidence showing that greenhouse gas forcing will exceed the likely bounds of natural variability (if it hasn’t already)?
Take a look at how the global average temperature has varied over the past 130 years (yearly averages with 11 year running mean in bold):
An indication of unforced natural variability is given by the year to year variation, amounting to 0.1 to 0.2 deg C on a yearly basis. As the Skeptical Science article shows, natural forcings can not explain the most recent warming, because they don’t exhibit a trend of the needed direction or magnitude.
Now let’s stipulate that it’s all due to longer term natural variation (as opposed to a forcing) of an unspecified kind. What would that mean for the planetary energy balance? If internal variations would have been responsible for most of the planetary warming, the earth would be emitting more energy to outer space than it receives, resulting in a negative radiative imbalance at the top of the atmosphere (or the energy would have to come from other parts of the earth’s system).
Neither is the case. It’s actually opposite: There is a positive radiation imbalance and other reservoirs (e.g. oceans, cryosphere) are also gaining more energy.
And then we haven’t even looked into the future yet. I recently posted this graph of two scenario’s that plausibly bracket a business as usual trajectory (red) and a stringent emission reduction trajectory (blue). The measured temperature increase up to now (which according to most scientists is strongly impacted by anthropogenic emissions) is given by the black line.
Judith’s estimates for the 21st century come down to a chance of warming of 0.25 + 0.75/2 = 0.625 versus a chance of cooling of 0.375, assuming natural factors having a 50% chance of either warming or cooling. So she deems the chance of warming to be roughly twice that of cooling, presumably even in a BAU scenario. Too bad that’s too long of a timeframe to place a climate bet on.
Look at how much the red -and even the blue- projections will likely deviate from the recent temperatures. I sure hope that there will be some magical counteracting cooling effect, but I haven’t seen any plausible evidence for such.
Postscript: From our email conversation, I understand her point of view better than before. But unlike the statement about the 20th century warming, which is not as far off from the IPCC as I had initially thought (except for the amount of uncertainty), her statement about the projected 21st century warming is hard for me to square with the mainstream scientific view, for which there is lots of evidence.
Tags: anthropogenic forcing, climate change, global warming, IPCC, Judith Curry, natural climate forcing, uncertainty
My view on climate change 
September 21, 2010 at 00:43
Hiya Bart,
Well, when I read Judith it makes sense to me. Let me use some made up figures here:
The IPCC estimates that 30% of CO2 is anthropogenic, + or – 10%
The IPCC estimates that that will cause 1.2 degrees warming without feedbacks, plus or minus 10%.
The IPCC estimates sensitivity at between 1.5 C and 4.5 C
Bart Verheggen estimates cooling from aerosols increasing by 0.2 C, plus or minus 10% (made up, but I’d love to know what you think…)
Ian Plimer estimates number of volcanic eruptions of Pinatubo size this century at 11.5, plus or minus 10% (still made up, but who knows…)
The variation between taking the low end of all these measurements (and you can add as many as you want, from solar changes to long term PDO cycles, etc., etc.,) and the high end gives some really big swings.
Judith I think is trying to put sensible bands around uncertainty. Which I think is very large. So large that it probably constrains the number of useful things we can say about climate change at this point in time.
Temperature change right now is what–about 1.2 C per century? And 2010 is going to be one of the hottest years of the last 100 or so, obviously. But we’re moving into the down cycle of a lot of things, as well. Won’t we really know a heckuva lot more by watching what happens to temps over the next 5 years than we learned over the past 5?
September 21, 2010 at 02:58
I asked this of Von Storch because I’m interested. What is your personal best guess for the amount of the last 30ish years of warming as caused by humans?
I’ve never claimed a number in any sense. I’m not knowledgeable enough so when I ask, there is no potential backlash or trap or whatever. It’s a curiosity so any of your favorite sources would be interesting also.
September 21, 2010 at 03:25
yeah, let’s all wave our arms in the air and think up some numbers. That will give us something to argue about. And perhaps we can call it science because there are some scientists waving their arms around and saying numbers as well.
Meanwhile, back in the lab, scientists are using actual scientific approaches to estimating probabilities of various scenarios…
I know which approach I’d like the politicians to base their deliberations on. And it ain’t armwaving.
September 21, 2010 at 09:58
Tom,
My beef is mostly with claiming equal evidence/equal portions of attribution for anthropogenic vs natural causes of recent and projected future climate change. I think that is seriously at odds with the the available evidence.
Regarding uncertainty, I wrote the following:
I.e. one could still assign high confidence to an uncertain statement if the statement itself accounts for this uncertainty.
We will always know more in 5 years time. That has always been the case and always will. Nobody would postpone investing in the stock market with the argument of “let’s wait 5 years, then we know who would have won the most”.
Jeff,
For the past 30 years most natural forcings didn’t have a strong trend in either direction; solar was arguably in a mild cooling direction and there were a couple of strong volcanoes. (see also fig 2.23 of AR4 for the time evolution of climate forcing)
For the past 30 years therefore, I think a decent guess would be that natural forcings didn’t have any effect on the temperature trend (and perhaps even more likely negative than positive). Which means that most likely all (and perhaps even more) of the warming of the past 30 years has been anthropogenic. Philipona et al (2009) estimate that at least for Europe declining aerosols contributed to the warming. Over North America though aerosol loading have stabilized while over Asia they’re still increasing, so their conclusions can not be extrapolated to the whole globe. They arrive at higher contributions for the direct aerosol effect than most other estimates though; the last word has not been spoken on that.
For the energy and temperature budget of the globe since pre-industrial, this paper by
Ramanathan and Feng (2009) is quite good (and a shorter one in PNAS). They write:
I.e. within the large uncertainties of both climate sensitivity and aerosol effects, earth has warmed up about as much as expected. Note that as the aerosol pollution will be cleaned up (it will, eventually, because of its adverse air quality effects) and as the climate equilibrates, hitherto masked (aerosol) and unrealized (ocean heat storage) warming will be unleashed.
I’ve been wanting to write more about the role of aerosols in all of this for ages, but never seem to get around to it. One day.
September 21, 2010 at 12:22
[…] Judith Curry on anthropogenic versus natural causes of global warming […]
September 21, 2010 at 13:28
> yeah, let’s all wave our arms in the air and think up some numbers.
I was wondering that too. Not having read Curry in detail: does she actually justify her choice of r/w/g in terms of refs to papers or IPCC, or is she just making this up?
September 21, 2010 at 13:59
William,
I haven’t seen any evidence for her weights; it’s her personal assessment. She does say she’ll get back to the subject of attribution. Her main point seems to be that the uncertainty is massive; how she translates that in the red area being as large as the green is still a mystery to me.
September 21, 2010 at 14:19
Hi Bart.
Why don’t you and Judith offer us your multivariate regressions of changes in temperature as a function of whatever are your preferred human and non-human influences?
And how do you both explain why the IPCC AR4 provided not a shred of econometric evidence for its claim that “most” global warming is with “90% certainty” attributable to us humans? I see no t-statistics or coefficients for relative attribution of the non-human influences that may account for as much as 49% of observed warming. Can climate scientists do basic statistics? NO, as Lord Oxburgh admitted at the House of Commons last week (not that he can either).
Anyway, I have just revisited the data I have from NOAA on temperature, solar surface radiation, atmospheric water vapour, relative humidity, windspeed, [CO2], etc etc at Point Barrow in Alaska (from 1960 though 2006). Why there? – because that is where the influence of atmospheric CO2 should be most evident, being high latitude, not much sun if any for half the year, and using Tmin, also said to be most affected by rising [CO2].
What do I find using multivariate regression analysis (unknown as that is to the IPCC in its AR4 WG1)?
Changes in Tmin from 1960 though 2006 are with better than 95% certainty attributable wholly to changes in the solar radiation (direct and diffuse, less albedo) on the ground at Pt Barrow, while the role of changes in [CO2] is with 99% certainty trivial and NEGATIVE as well as not stat. sig. The regression passes the Durbin-Watson test (2.813>2) for autocollinearity, and ALL tests for Multicollinearity (eg Tolerance .981 on both variables and VIF 1.019 on both, with Eigen values also well within the benchmark).
Bart, can you name a single climate scientist who can or has done regression analysis? Forget Schmidt and Foster.
NOW you know why AR4 does not report regression analysis, because if it did it would be end of story.
September 21, 2010 at 15:01
Tim,
E.g. How natural and anthropogenic influences alter global and regional
surface temperatures: 1889 to 2006
Judith L. Lean and David H. Rind
And please don’t rehash all your local correlations; I’m not interested. Perhaps E&E is.
September 21, 2010 at 16:49
Astounding revelations and arm waving from Curry– “it’s her personal assessment”. She has seemingly not even consulted the literature on this subject. That quite simply does not cut it and is highly unprofessional and irresponsible on her part.
Curry admonishes the IPCC for not quantifying uncertainties properly, then she goes and engage sin this subjective, unsubstantiated, hand-waiving, and juvenile flag analogy.
If this is going to be the “substance” of her arguments, then I give up on Curry as a scientist.
September 21, 2010 at 21:47
Thanks for your reply Bart, I’ve read the papers with interest before work.
September 21, 2010 at 22:20
Bart: Judith Lean’s use of TOA total solar irradiance is quite different from my in situ surface level solar radiation (“Avglo” in the NOAA data): the TOA is of course invariant night and day 24/365 and has no local variabilility. “Avglo” varies enormously of course according to location and temporally.
Your dismissive comment : “And please don’t rehash all your local correlations; I’m not interested” is if I may say so rather silly. Surely you accept that NASA’s global Gistemp is of course the outcome of aggregation and then averaging of LOCAL temperarure readings. If your model does not hold at any single location on earth then it will also fail at the global level, when you do the necessary Durbin-Watson and multicollinearity tests. But you can’t/won’t.
September 21, 2010 at 22:37
absolutely bizarre claim.
i would be seriously surprised, if i hadn t been reading a lot from Judith over the last year.
this is complete garbage!
September 21, 2010 at 22:52
i only had time for a short look at the article, but i am still shocked.
over the first half of comments Judith basically offers zero support for her beliefs.
expanding the “unknown” is a typically anti-science and denialist tactic, that we know from campaigns in the past. classic.
September 21, 2010 at 23:03
curryja says:
September 17, 2010 at 5:19 am
Girma, I just spotted this discussion at Skeptical Science (which I have now added to the weblog) http://www.skepticalscience.com/should_earth_be_cooling.html. It discusses natural variability over the last decade, which has dominated the temperature signal. The temperature signal results from an interplay of greenhouse forcing and natural variability, with solar and the PDO contributing to cooling over the last decade.
sorry, i had to stop reading there. Judith curry is basing her flag colour distribution on her belief that the last decade was cooling and the pink colour of the moon.
impressive evidence.
September 22, 2010 at 00:09
Bart,
I’m a little surprised by the E&E attack, unless it is required to attack E&E every 6 months for membership in the climate club. Certainly you don’t disagree with MM’s various critiques of the hockeysticks. Of all things in climate science, that’s one where I’ve spent a lot of time and the Mann team was, is and likely will be wrong in the foreseeable future. I’m not trying to hijack the thread but in my opinion E&E did a great service to climate science by publishing their articles where others actively blocked them.
September 22, 2010 at 00:35
> I’m not trying to hijack the thread
Good, let’s ignore that stinkbomb.
September 22, 2010 at 05:42
Jeff and Bart: I’d add the 2004 paper by Meehl et al , the abstract of which reads: “The late-twentieth-century warming can only be reproduced in the model with anthropogenic forcing (mainly GHGs), while the early twentieth-century warming is mainly caused by natural forcing in the model (mainly solar).”
And speaking of arm-waving: Tom, please elaborate on how “we’re moving into the down cycle of a lot of things” and what exactly you think this means for climate. Are you referring to winter?
September 22, 2010 at 07:45
Down cycle?
I rather thought that the low solar input of the last few years indicates that that particular cycle has nowhere to go but up.
September 22, 2010 at 09:19
Never mind that the fact that even in a very deep solar minimum with the PDO allegedly in a cool phase we still have record warm global temperatures. That sais something about the relative strength of the greenhouse warming methinks.
Tim,
I’ll pay attention to what you’re saying if and when you start understanding the difference between local and global.
Jeff,
E&E will publish anything as long as it can be interpreted to shed doubt on AGW. That not everything in it is downright false doesn’t make it a good or trustworthy journal; it is clearly biased. But admittedly, it was just a dig that wasn’t needed to make my point. Tim’s been getting on my nerves before, that’s probably why. I’m not opining on hockeysticks.
September 22, 2010 at 11:16
Fair enough Bart, but I would like to see someone from the Climate mainstream make some firm comments on the paleo hockeysticks someday. It is time, and the science is stronger without them.
September 22, 2010 at 14:21
Bart: I’ll pay attention to what you’re saying if and when you start understanding the difference between local and global, given that the latter is the aggregate of the former averaged by dividing by the number of area grids covered by the local.
September 22, 2010 at 14:48
That’s simply your unsubstantiated opinion, and those working in the field are most likely going to ignore it …
September 22, 2010 at 17:58
I don’t think this is a good spot for that discussion dhog.
Sorry Bart.
September 22, 2010 at 20:40
Tim
How does this differ from the argument that, because my sister-in-law lost 30 pounds at the age of 14 (serious illness), it is demonstrated that it is false that children gain weight in their teenage years?
September 22, 2010 at 23:27
I was under the impression that about 1/2 of the warming from 1850 to-date occurred prior to any significant increase in CO2 emissions, and about 1/2 after. So doesn’t that imply that natural variability could have possibly accounted for 1/2 of the warming to-date?
September 23, 2010 at 01:13
Curry seems to make the odd assumption that if there is observed warming over a time period, the effect of natural influences must be in the warming direction. I can’t figure out why she would be quoting from the nice post at Skeptical Science on natural forcings as if it supports her position, when it does the opposite. It indeed shows that all possible natural forcings should be in the direction of cooling, at least in recent decades, which means the effect of anthropogenic forcings is even greater.
I’m not seeing how Curry’s position is close to that of the IPCC. “Equal evidence” might imply that there’s a 50-50 chance of either anthropogenic or natural factors being responsible for the observed trend since mid-century, when they assign “very likely” (> 90%) to the anthropogenic case. Hers is closer to the 2nd IPCC report, which assigned a “more likely than not” conclusion, back when there were more unknowns and observations in the lower troposphere conflicted. In addition, the IPCC also makes a similar conclusion as the Skeptical Science link above – in that the best estimate is that natural forcings lead to a small offset of anthropogenic warming, meaning anthropogenic warming was > 100% of observed. The conclusion is probably strengthened a little with recent observations (as much as a few years can do) of very low solar activity and the warming trend still prevailing.
http://www.ipcc.ch/publications_and_data/ar4/wg1/en/figure-spm-4.html
The IPCC “very likely” conclusion on observed warming being mostly anthropogenic is pretty wishy-washy in my view. Evidence is stronger than that. I suppose it accounts for the “unknown unknowns”, which you can apply pretty much to anything in life.
September 23, 2010 at 02:26
Richard Simons: do read Karl Popper’s The poverty of historicism.
September 23, 2010 at 08:30
MarkB,
The confusion comes from the translation of the IPCC language in the Italian flag. Curry’s equal weights are a reflection not of the confidence level (which is 100%-white) but of “most” of the warming where she deviates from IPCC to make that “half of the warming”
RickA,
Check out fig 2.23 of AR4 (in my earlier reply to Jeff), to see how different forcings changed over time.
September 23, 2010 at 21:26
Perhaps a slightly more relevant Skeptical Science article would be the one I wrote on Quantifying the human contribution to global warming. I think it would make for useful reading for those (like Curry) who claim the current and future warmings could remotely be natural.
http://www.skepticalscience.com/Quantifying-the-human-contribution-to-global-warming.html
I have to constantly remind myself that Judith Curry is a climate scientist, because based on her writings it’s just so hard to believe.
September 24, 2010 at 15:02
Dana: [edit]
There’s an old saying, those who can, do, those who can’t, teach, those who can’t teach, teach teachers, and those who can’t do even that, do climate research, and fail yet again. You are in the latter category. And then you have the gall to add “I have to constantly remind myself that Judith Curry is a climate scientist, because based on her writings it’s just so hard to believe”. Really, 140 articles in journals like GRL, JGR, and JoC, plus a book (Thermodynamics of Oceans & Atmosphere) of which you are incapable of understanding a single page?
You link to your own “article” but that is largely plagiarised, and like its main source (AR4 2007), is incapable of providing let alone assessing time series data, which is what you have to do if you want to “Quantify the human contribution to global warming”.
There is something called multivariate regression analysis that alone is capable of providing answers to your quest, to “quantify the human contribution to global warming”. Like ALL at the IPCC, that is beyond you, but I have done it at many locations in USA and Australia, and NOWHERE does anthropogenic CO2 play any role at all, and as the other “radiative forcing” effects in your Fig. 4, like CH4, have no time series data showing any increase since 1990, your piece will forever remain unpublished.
When you have learnt to do regression analysis do get back to us.
September 24, 2010 at 19:00
Tim,
– Try to make your point without mudslinging
– Articles at SkepticalScience are meant to convey the basic science to a lay audience, so of course they are based on that science rather than laying out new results (it’s not a scientific journal). A charge of plagiarism is just ridiculous.
– Do your analyses on some global data and maybe you’d have something interesting.
– Don’t ignore the physics
September 24, 2010 at 20:52
Tim, actually the quote (from H.L. Mencken) is “Those who can — do. Those who can’t — teach.” I’m quite certain that Mr. Mencken did not share your obvious disdain for scientists. If you’re going to paraphrase a saying, then say so, rather than attributing your personal opinions to others. I doubt Mr. Mencken would appreciate your inference that he believed climate scientists are morons.
I was also quite obviously referring to Judith Curry’s blog writings, and not her professional writings. If I didn’t make that clear enough for you to be able to comprehend, I apologize.
I also suggest you look up the definition of the term “plagiarism”, since you do not seem to understand what the word means. As Bart notes, your accusation is utterly absurd.
And I’ll echo Bart’s suggestion that if you want to assess the impacts of radiative forcings on *global* warming, that you examine *global* temperature data.
And finally as to your claim that anthropogenic GHGs play no role in surface temperature changes, again I will echo Bart’s suggestion that you “Don’t ignore the physics.”
September 24, 2010 at 22:55
Bart;
Keith’s comment was on the Monckton thread…;)
September 25, 2010 at 09:29
Dana: I apologise – I was wrong to charge you with plagiarism on the strength only of your Fig.1 having no source.
I did not know HL Mencken was the author of the saying “those who can do, those who can’t, teach…” – but he also said “The whole aim of practical politics [read… climate science] is to keep the populace alarmed (and hence clamorous to be led to safety) by menacing it with an endless series of hobgoblins, all of them imaginary”.
Your piece provided no evidence for its radiative forcincg formula, have you ever tried it anywhere globally or locally? AFTER testing for stationarity, autocorrelation, and multicollinearity etc. you will find your formula
dT = λ*dF
has never been confirmed or verified.
You went on: “So now to calculate the change in temperature, we just need to know the climate sensitivity. Studies have given a possible range of values of 2-4.5°C warming for a doubling of CO2 (IPCC 2007)”.
That is a very wide range which itself implies there have been no retrospective observational studies to validate your equation.
Using these values it’s a simple task to put the climate sensitivity into the units we need, using the formulas above:
λ = dT/dF = dT/(5.35 * ln[2])= [2 to 4.5°C]/3.7 = 0.54 to 1.2°C/(W/m2)”.
As we have already had 0.7-0.8 oC since 1900 from 40% increases in [CO2], that means the next 60% increase in [CO2] (to bring it to 100% more than in 1900) would on your formula only raise GMT by 0.4 oC. So why the hysteria at Copenhagen and soon at Cancun?
The IPCC’s hobgoblin of 4.5 oC (3.7 oC more for 60% than the 0.8 oC we’ve had from the 40% increase in [CO2] since 1900) is much more alarming than yours but equally fictitious.
Your equation has no merit as it is being refuted everywhere it is tested against local temperatures, and pace Bart, the global temperature anomaly is the sum of the local divided by the number thereof.
September 25, 2010 at 15:39
Tim Curtin,
Please enlighten us about what we should make of Popper’s **The Poverty of Historicism**.
September 25, 2010 at 16:59
Willard.
Thanks. To my surprise when I arrived at LSE in 1961 to read Economics, I was told to get hold of Popper’s book on Historicism of all things. I found that following Einstein, Popper declared that the appearance of a black swan was enough to invalidate a hypothesis that since all known swans in the NH were white, all swans globally were white. I suspect it was James Cook who was the first NH person to note the existence of black swans at what is now Freemantle in Western Australia’.
Wiki again: “Falsifiability, particularly testability, is an important concept in science and the philosophy of science. The concept was made popular by Karl Popper in his philosophical analysis of the scientific method. Popper concluded that a hypothesis, proposition, or theory is “scientific” only if it is, among other things, falsifiable. That is, falsifiability is a necessary (but not sufficient) criterion for scientific ideas. Popper asserted that unfalsifiable statements are non-scientific, although not without relevance. For example, meta-physical or religious propositions have cultural or spiritual meaning, and the ancient metaphysical and unfalsifiable idea of the existence of atoms has led to corresponding falsifiable modern theories. A falsifiable theory that has withstood severe scientific testing is said to be corroborated by past experience, though in Popper’s view this is not equivalent with confirmation and does not guarantee that the theory is true or even partially true”.
“In work beginning in the 1930s, Popper gave falsifiability a renewed emphasis as a criterion of empirical statements in science.
Popper noticed that two types of statements are of particular value to scientists.
The first are statements of observations, such as “this is a white swan.” Logicians call these statements singular existential statements, since they assert the existence of some particular thing. They are equivalent to a propositional calculus statement of the form: There exists an x such that x is a swan, and x is white.
The second are statements that categorize all instances of something, such as “all swans are white”. Logicians call these statements universal. They are usually parsed in the form: For all x, if x is a swan, then x is white. Scientific [and climate “laws”] laws are commonly supposed to be of this type. One difficult question in the methodology of science is: How does one move from observations to laws? How can one validly infer a universal statement from any number of existential statements?
Inductivist methodology supposed that one can somehow move from a series of singular existential statements to a universal statement. That is, that one can move from ‘this is a white swan’, ‘that is a white swan’, and so on, to a universal statement such as ‘all swans are white’. This method is clearly deductively invalid, since it is always possible that there may be a non-white swan that has eluded observation (and, in fact, the discovery of the Australian black swan demonstrated the deductive invalidity of this particular statement).”
Historicism
Theories of history or politics that allegedly predict future events have a logical form that renders them neither falsifiable nor verifiable. They claim that for every historically significant event, there exists an historical or economic law that determines the way in which events proceeded. Failure to identify the law does not mean that it does not exist, yet an event that satisfies the law does not prove the general case. Evaluation of such claims is at best difficult. On this basis, Popper “fundamentally critized historicism in the sense of any preordained prediction of history”[16], and argued that neither Marxism nor psychoanalysis was science [16], although both made such claims. Again, this does not mean that any of these types of theories is necessarily incorrect. Popper considered falsifiability a test of whether theories are scientific, not of whether propositions that they contain or support are true.
Albert Einstein is reported to have said: No amount of experimentation can ever prove me right; a single experiment can prove me wrong. (paraphrased)[17][18][19].
The criterion of the scientific status of a theory is its falsifiability, or refutability, or testability. — Karl Popper, (Popper, CR, 36)”
Now me: the whole problem with climate “science” is that Dana’s admirable summary is easily falsifiable everywhere on the globe, as NOWHERE can it be shown that rising [CO2] is associated with rising GMT.
Neither Dana nor Bart has shown any such evidence, as they prefer to use “global” temperatures as the dependent variable in a uni-variable regression analysis of [CO2] ignoring standard tests for autocorrelation and multicollinearity, and refuse to allow the first-differences method that addresses failure of absolute values to pass those tests.
My own analyses have uncovered multiple black swans, from Pt Barrow to Mauna Loa to Cape Grim, at none of which is there any evidence to show that changes in [CO2] have ANY impact on temperature trends at those places. How many black swans will it take for you, Bart, and Dana, to admit that your AGW hypothesis is fatally flawed?
September 25, 2010 at 20:13
Tim Curtin,
Thank you for the reminder. Without entering into a debate over the merits about falsificationism, I’ll simply point out that It’s tough to endorse it and say things like:
> AFTER testing for stationarity, autocorrelation, and multicollinearity etc. you will find your formula […] has never been confirmed or verified.
or
> That is a very wide range which itself implies there have been no retrospective observational studies to validate your equation.
Falsificationism holds that there is no way to confirm or verify any scientific statement.
***
I’ll also note that there is a problem with the interpretation of such and such location as “black swans”. Finding one spot that contradicts P only refutes that P holds at all time everywhere. Unless you can find such a universal claim, you have not proven anything.
Besides, as you accumulate counterexamples, you will have to induce something to reach a complete refutation of the universal claim. This induction does not fit very well into the falsificationist framework ;-)
September 25, 2010 at 20:19
By
> Unless you can find such a universal claim, you have not proven anything.
I meant of course:
> Unless you can find such a universal claim, you have not refuted anything.
So the conjecture about the overall warming is not refuted by claiming that a subset of the dataset, unless of course someone claimed otherwise. This would mean that climate temperatures has some kind of statistical self-similarity. This would be a very counterintuitive claim, to say the least.
September 25, 2010 at 20:21
Sorry to type too fast:
> So the conjecture about the overall warming is not refuted by claiming that a subset of the dataset, unless of course someone claimed otherwise.
lacks
> So the conjecture of the overall warming is not refuted by claiming that a subset of the dataset has not warmed, unless of course someone claimed otherwise, i.e. that the overall warming also means a warming anyywhere.
September 25, 2010 at 20:50
Tim, I find your last comment to me rather strange, as though you only read parts of my article and ignored the rest. I’ll ignore the fact that you’re once again putting words in Mr. Mencken’s mouth and move on to your comments on my article.
The formula dT = λ*dF is an approximation based on empirical observations, as I explained and linked to a paper (Myhre 1998) in which the formulae were derived. Thus your comment that this formula “has never been confirmed or verified” is flat-out wrong.
I wrote another article on climate sensitivity which demonstrates that your next comment, that “there have been no retrospective observational studies to validate [the IPCC range of climate sensitivity]” is also flat-out wrong.
http://skepticalscience.com/detailed-look-at-climate-sensitivity.html
Your next comment that “the next 60% increase in [CO2] (to bring it to 100% more than in 1900) would on your formula only raise GMT by 0.4 oC” is – everyone say it with me – also flat-out wrong.
In fact I went through this calculation in my wiki. The formula you’re using to arrive at your incorrect conclusion gives the climate sensitivity parameter in °C/[W m-2]. It’s not the climate sensitivity in °C for 2xCO2, which is 2-4.5°C. I suggest you re-read the article.
I have no idea what you’re talking about when you refer to “The IPCC’s hobgoblin of 4.5 oC”. Most IPCC scenarios project 3°C or less warming by 2100 (though higher emissions scenarios are as high as about 6°C by that date).
I suggest you do a bit more research before criticizing others.
September 25, 2010 at 21:25
dana, check over at Tim Lambert, where Curtin had his own thread.
http://scienceblogs.com/deltoid/2009/03/tim_curtin_thread.php
Beware of what you get into when discussing with him.
September 25, 2010 at 21:50
Heh that’s funny. Thanks for the heads-up, Marco.
September 26, 2010 at 04:50
Willard: all the same, a black swan is enough to sink any and all hypotheses.
I confess to being surprised when I found that my regressions on the climate data for pt barrow in the Alaskan Arctic and for Hilo at the foot of equatorial Mauna Loa agreed that “aqueous water vapour” (to use Arrhenius’ term) is the prime mover of both Tmax and Tmin at those locations, that increases in [CO2] play no role at all, and that the Sun (solar SURFACE radiation geddit?) does not affect Tmin (what a surprise!) but does affect Tmax (another surprise) to 99% probability. Now why would that be?
Arrhenius’ mostly brilliant paper (nearly worth another Nobel) noted how the atmosphere’s opacity affected climate (through its impact on aqueous H2O and solar SURFACE radiation). NOAA had people previous to indoctrination by Hansen’s GISS who had read Arrhenius and collected data on all his variables until somebody (was it Jim?) put a stop to it in 2006. Svante lacked our computers and did not in fact do real experiments, which explains why his mono-variable [CO2] calculations have failed miserably.
September 26, 2010 at 10:56
Thanks Marco for the plug.
Dana: have you tried your hobgoblin formula against real data data anywhere? Try Huston: for your CS of 2, it produces mean temperature in 2006 of 22.96 against the actual 20.97 (using ln of CO2 in 1960 and in 2006), and for your CS of 4.5 it produces a forecast of 25.46.
So your magic formula is only out by 2oC and 4.5oC respectively.
Where do you live? let’s see how the hobgoblin performs there over that period (1960-2006) or to 2009 if you have the temperatures to then.
September 26, 2010 at 13:08
Tim Curtin,
I’m not at all interested in having this thread degenerate into your list of local correlations. You have refuted nothing but strawmen of your own imagination. You can continue doing so at your own internet-home, but not at mine. You’re on moderation. You’re welcome to participate in the discussion topic at hand, but please don’t hijack the thread. Thanks!
September 26, 2010 at 14:48
Bart: You have already had me on moderation for yonks. You allow Dana to repeat the absurd IPCC equation on THIS thread, and will not allow me to comment thereon. In TRUTH (a rare commodity out here), you should have moderated Dana out if you are not prepared to allow comments on his post.
It would help you if you would actually catch up on Popper – and grasp that Gistemp’s Global (sic) temps are actually the aggregate of n grids divided by n.
And try actually reading Judith Curry’s brilliant papers on Arctic temperatures and sea ice, and then apologise to her and me. My regressions of the Pt Barrow data from NOAA totally vindicate her analysis of the Russian data for that part of the Arctic (“Water vapor feedback over the Arctic Ocean” JGR 1995).
September 26, 2010 at 15:16
This Comment of mine on Dana’s post (which was not moderated) appears to have been moderated into oblivion. As it raises rather huge issues, I will try again, despite risking Bart’s ire:
Dana again: actually all you need to do is to add 2oC to your temperature in 1960 for your model’s prediction for 2006 and check that against the actual (I made a slight error in my previous, the forecast for Houston in 2006 was actually 22.78 with CS=2, and 25.3 for CS=4.5). Your formula yields increases in Tmean EVERYWHERE of 2oC and 4.49oC from 1960 to 2006 using [CO2] as at Mauna Loa.
Arrhenius was much more refined, with estimates by latitude, and was not as far out for Barrow as you are at Houston.
And your formula really is a hobgoblin, with predictions of 6-15 for doubling if your CS are constants. If they are not, your formula is of course circular, since the CS actually determine the outcomes, and they are assumptions (of the desired result) and are not derived from any empirical evidence whatsoever.
Can you not see that by assuming your CS, you assume your results?
September 26, 2010 at 16:09
> [A] black swan is enough to sink any and all hypotheses.
The existence of a black swan only disproves the claim that all swans are always white. This falsification is not out of logical necessity: we must take into account the background knowledge. That is, that refutations only works if we know what whiteness is, that blackness is not whiteness, that there can’t be white and black swans, that we should not decide to revise our ontology of swans instead.
Tim Curtin should be able to tell how a statement about local temperatures can refute a statement about global temperatures. Unless we adopt some kind of statistical self-similarity between the local and the global, I fail to see how the reasoning works exactly. On the face of it, showing that such and such regions is not warming does not refute the claim that the sum of the regions warm.
The best way to disprove the claim that the global temperatures do not warm would be to prove that they indeed do not warm. For now, the induction that Tim Curtin provides is too weak and appears as a mere rhetorical device.
That this rhetorical device proceeds by induction is intriguing, considering the falsificationist setting that Tim Curtin sets up his refutation, for Popper’s insistence on refutation is motivated by his conception of science as a system to make empirical deductions.
September 26, 2010 at 17:10
Willard: you said “Tim Curtin should be able to tell how a statement about local temperatures can refute a statement about global temperatures”.
Good point. But what if ALL local temperatures refute the statements about Global average temperatures?
And again when you said “On the face of it, showing that such and such region is not warming does not refute the claim that the sum of the regions warm”. Again, good point, except that if you had said the “average” instead of “the sum” you would have been more right. Take care!
And what if ALL regions collectively show no such warming? There is massive evidence that in the USA, UK, and Australia there is a coordinated determination to lower the temperatures that were recorded prior to 2000 in order to raise the “anomalies” post-2000. How can you be so sure that Gistemp/Hadley et al accurately portray GMT?
Then Willard said: “The best way to disprove the claim that the global temperatures do not warm would be to prove that they indeed do not warm. For now, the induction that Tim Curtin provides is too weak and appears as a mere rhetorical device”.
Well said! But what if the “warming” since 1900 is based on the absence of temperature records (in Gistemp, Hadley et al.) in 1900 of hot places like almost all Central America, 100% of all Africa apart from Cape Town and Cairo, and almost all of S.E. Asia ?
Willard added: “That this rhetorical device proceeds by induction is intriguing, considering the falsificationist setting that Tim Curtin sets up his refutation, for Popper’s insistence on refutation is motivated by his conception of science as a system to make empirical deductions”
Willard, I am sorry to say I suspect Bart will not allow my final Popperian refutation of Dana/IPCC’s magic pudding formula to appear here.
But let me try again: Bart, IPCC, and Dana et all, claim that rising [CO2] will raise GMT pro rata. If I show that NOWHERE on earth, as I can, that there is NO evidence that rising [CO2] has any measurable (i.e. statistically significant) impact on temperature, how can the GLOBAL average controvert the individual site readings?
Dear Bart: just show me your regression analysis of changes in temperatures (all of Tmax, Tmin, Tave, Tdaily ave) in Amsterdam against changes in [CO2], “aqueous water vapor” (“H2O”), and “SSR” (total solar surface radiation net of albedo) since 1958.
September 26, 2010 at 17:43
Tim,
I’m well aware that an average is made up of its parts. I’m also aware that the behavior of a couple of parts is not necessarily the same as the behavior of the grand average. I can hardly imagine you not being aware of that, but your incessant local correlation betray some sort of misunderstanding on your part.
Dana’s point was directly relevant to the division into natural and anthropogenic causes of climate change, which was a major point of this post. The problem I have with your comments is only partly that they’re off topic; if it doesn’t stray too far away, I usually don’t make a big deal about it. But the repetitive nature of your argument, which is entirely moot, just adds nothing to the discussion. Let’s just agree to disagree about it rather then endlessly repeating ourselves. If you have something new to say, please do so. But I will not allow endless repetition.
September 26, 2010 at 19:42
Tim, as Bart notes, my initial comment was directly in response to the part of this article discussing the attribution of the recent warming to natural and anthropogenic effects. In fact it referenced an article at Skeptical Science; thus I linked to my perhaps more relevant article on the same site which demonstrated that anthropogenic greenhouse gas emissions can account for ~100% of the warming over the past half century.
Among other silly statements, you then claimed that my formula was wrong because the numbers don’t work out for the local temps at Houston, Texas. As others have noted many times, you can’t apply a formula or effect acting on a global scale to local temperatures. In fact one method of deriving climate sensitivity is to look at changes in global temperatures over recent decades. In another recent article, I showed that applying observed global temperature changes to James Hansen’s 1988 global warming projections yields a climate sensitivity of approximately 3.4°C for 2xCO2.
http://skepticalscience.com/A-detailed-look-at-Hansens-1988-projections.html
Sorry Bart I hope that wasn’t too far off-topic. I’m just trying to illustrate the difference between looking at local vs. global temps, even though that’s not what this article is about.
Regardless, when examining the underlying physics it’s quite clear that anthropogenic causes are the dominant factor in current and future warming trends, and someone with Judith Curry’s physics background should understand that.
September 27, 2010 at 09:22
Dana: your comments about Judith Curry are risible once again, she’s forgotten more physics than probably you have ever known.
Your own paper it seems to me confuses the outcome of doubling of [CO2] in oC with lambda, which is the constant for “climate sensitivity”. Using Wiki’s number for lambda, 0.8, rather than your much higher estimates, still somewhat overstates warming at a place like Houston – and seriously understates the actual at Pt Barrow. That is the problem with the Myhre et al/IPCC equations you use, they are one size fits all. And in my view the physics underlying the radiative forcing concept is tenuous at best and otherwise downright misleading.
The trouble with an average is that it filters out the variability that needs to be explained if you seek to discriminate between anthropogenic and non-anthropogenic causes. Your papers fall far short of doing that.
And with all respect due to Bart and his Blog, what will he say when I complete regressions for every grid in the NASA database that both individually and in aggregate show minimal correlation between changes in [CO2] and in any of Tmin, Tmax, and Tave?
September 27, 2010 at 09:36
Tim,
If and when you have something to report on global (or hemispheric) temperature regression, I’ll be interested indeed.
September 27, 2010 at 11:03
Bart, I’ll send you my paper. Thanks for the link, in fact I already have Stern & Kaufmann.
Almost first up they say “Few researchers have used time domain econometrics methods to analyze climate change. Apart from Kaufmann and Stern (1997) and Stern and Kaufmann (1999), only Tol and de Vos (1993, 1998), Tol (1994), and Richards (1993) explicitly use econometric time series methods to investigate the causes of climate change, though Schönwiese (1994) uses an econometric type model with lagged independent variables.”
Why have so few done this? Interestingly 2 of those that have, David Stern himself and Richard Tol are far from being diehards on CAGW, although to get grants they have to be careful to be politically correct, especially the former given the climate here (as I know to my cost, and I am not talking about our cold winter at present).
Note the use by S & K of “may” in the following suumary of their findings:
“The results show that Northern and Southern hemisphere temperatures share a common trend that may be primarily due to greenhouse gases emitted by human activity and changes in solar irradiance, while the difference between the hemispheric temperature series may be primarily associated with anthropogenic sulfur emissions”.
The “mays” are fully justified as the paper omits consideration of all non-anthropogenic variables, dealing only with GHGs, aerosols, apart from the Lean TSI data. Arrhenius took into account “aqueous water vapour” and opacity of the sky, two critical omitted variables in the S&K paper, especially in the context of this thread on Judith Curry. If you mostly consider only one class of variables, your results are likely to be, well, one-sided.
September 28, 2010 at 04:16
“The Foolish reject what they see,
not what they think;
the wise reject what they think,
not what they see.”
– Huang Po
September 28, 2010 at 10:19
Tim “…and I am not talking about our cold winter at present.”
http://www.bom.gov.au/climate/current/season/aus/summary.shtml
No sign of a cold winter in Oz according to BOM.
September 28, 2010 at 13:12
Tim Curtin,
Slander and conspiratorial rants are off limits here. I removed your comment.
September 28, 2010 at 15:14
I think this hypothesis lies at the heart of Tim Curtin’s argument:
> But what if ALL local temperatures refute the statements about Global average temperatures?
What if, indeed.
> And what if ALL regions collectively show no such warming?
What if, here again.
> But what if the “warming” since 1900 is based on the absence of temperature records (in Gistemp, Hadley et al.) in 1900 of hot places like almost all Central America, 100% of all Africa apart from Cape Town and Cairo, and almost all of S.E. Asia ?
What if, here again.
> If I show that NOWHERE on earth, as I can, that there is NO evidence that rising [CO2] has any measurable (i.e. statistically significant) impact on temperature, how can the GLOBAL average controvert the individual site readings?
Only a if here.
What we can see is that the hypothesis about local temperatures is there to prove that the global temperatures are not warming. But we already know that it’s not what the global temperatures we have shows. We should suppose here that either it warms, or not: you can’t have both.
So the different interpretations of the global temperatures must be explained. Here is Tim Curtin’s explanation:
> There is massive evidence that in the USA, UK, and Australia there is a coordinated determination to lower the temperatures that were recorded prior to 2000 in order to raise the “anomalies” post-2000. How can you be so sure that Gistemp/Hadley et al accurately portray GMT?
But why all this kerkuffle about local temperatures when we have “massive evidence” of “coordinated determination”?
Let’s wonder why.
Let’s wonder why.
PS: I stand corrected about the “sum” of global temperatures.
September 28, 2010 at 16:57
Willard, oh dear…..so I wonder if Tim also believes that the folks at RSS and UAH also in on this conspiracy to “hide the warming”?
September 28, 2010 at 21:08
Tim Curtin,
Please take it to the open thread. Your assertions are off topic here. Also on the open thread, keep accusations of fraud at the door and leave a link rather than a pasted document.
Thanks.
October 5, 2010 at 13:19
Bart, you say “If internal variations would have been responsible for most of the planetary warming, the earth would be emitting more energy to outer space than it receives, resulting in a negative radiative imbalance at the top of the atmosphere (or the energy would have to come from other parts of the earth’s system).”
I’m not sure how you could say this with a straight face. Regardless of the cause of any warming, it must mean that the energy content of the earth is increasing,* therefore the earth would have to be emitting LESS energy than it receives.
*Unless the energy has come from another source within the earth system, such as latent heat or a reduction in the speed of ocean currents. There is no evidence for either of these being the case.
October 7, 2010 at 08:53
Alex,
It depends on the sequence of events.
A warmer earth will radiate more energy than a cooler earth, regardless of the cause of the warming.
If the surface warming is from internal variability without any apparent cause, the result would be that the earth radiates more heat away. A consequence of that would be a negative radiative imbalance at the top of the atmosphere (more energy leaving than coming in), which would trigger a negative feedback: The planet will cool again in order to regain radiative equilibrium. I.e. a pure random warming would be counteracted to prevent the earth from getting further and further removed from radiative equilibrium.
Unless, as both you and I said, the energy responsible for surface warming came from other parts of the earth system (e.g. the deep ocean, cryosphere). Indeed, there is no evidence for that being the case; to the contrary: All parts of the climate system seem to be gaining energy.
What you’re saying is basically that the energy content of the earth can’t just increase on its own without a forcing or internal shifting around of energy being responsible. Indeed.
October 7, 2010 at 14:16
Bart,
“A warmer earth will radiate more energy than a cooler earth, regardless of the cause of the warming.”
You should have stopped there.
“If the surface warming is from internal variability without any apparent cause, the result would be that the earth radiates more heat away.”
No! The amount of heat coming in is not changing. The surface is warming. Therefore there must be less heat going out. Regardless of whether we know the cause or not, if the surface is warming, and latent heat or conversion of mechanical energy to heat are not the cause, the result must be that the earth is getting more heat in than it is radiating out. Anything else defies physics. Just because we don’t know the mechanism doesn’t mean that it ain’t so.
“What you’re saying is basically that the energy content of the earth can’t just increase on its own without a forcing or internal shifting around of energy being responsible.”
Yes, although it depends on what you mean by forcing. There might be a forcing we don’t know about. For example, a change in the distribution of cloud could, without a change in the overall albedo, lead to more heat being retained. So could a change in water vapor content. I doubt we have the observations to confirm or deny either.
You say it depends on the sequence of events. I think you are getting confused between a warming earth and a warmer earth. Or perhaps we both are? These things are by no means straightforward, and the tendency of scientists to look at these issues in terms of energy balance (which never exists) rather than analyzing the processes tends to make for confusion.
October 7, 2010 at 14:31
Alex,
If the surface is warming, the
resultcause must be that the earth is getting more heat energy in than it is radiating out.An object getting warmer or cooler is the result of an energy imbalance.
Now, in the hypothetical situation that an energy imbalance did not cause the planet to warm, but rather it did so just by random variations happening to wander off in a certain direction, the situation arises that I described: The planet will seek to regain equilibrium because of a negative energy imbalance. I.e. the planet can not just wonder off too far from equilibrium without being pulled back by this negative feedback. Unless of course a forcing is acting on the system, pushing it into a certain direction until a new equilibrium is achieved (eg by radiating more energy out, which as a consequence heats up the planet).
The confusion may indeed arise from a warmer vs a warming planet.
October 8, 2010 at 09:38
Bart,
I think we are getting close to agreeing. If the issue arises in the real world, the problem will be differentiating between random variation and unobserved forcing (possibly along the lines I postulated).
Let’s leave it at that.
November 1, 2010 at 17:17
Bart:
I thought it was the consensus that solar minimums play no role in global mean temperature? If we’re discussing the consensus, why bring it up?
November 1, 2010 at 18:22
Bart, you wrote above
> All parts of the climate system seem to be gaining energy.
Even the facts aren’t agreed on, at least by Roy Spencer:
“data updated through yesterday (October 27). Needless to say, there is no end in sight to the cooling.”
http://www.drroyspencer.com/2010/10/bottom-falling-out-of-global-ocean-surface-temperatures/
I’m not sure if this is seasonally adjusted. The “no end in sight” seems to suggest a catastrophic cooling, rather than even the ‘natural cycles’ he favored earlier.
But blog text is just confusing.
Can you point to published papers?
November 1, 2010 at 19:11
Carrick, strawman. No one claims a solar minimum has no effect on global mean temperature. In fact, you can find plenty of papers attempting to quantify the effect of the (position in the) solar cycle on global mean temperatures. The effect is limited, about 0.1-0.2 degrees from bottom to top.
November 6, 2010 at 21:36
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