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BBC contrarian top 10

Filed under: — gavin @ 13 November 2007

There is an interesting, if predictable, piece up on the BBC website devoted to investigating whether there is any ‘consensus’ among the various contrarians on why climate change isn’t happening (or if it is, it isn’t caused by human activity or if it is why it won’t be important, or if it is important, why nothing can be done etc.). Bottom line? The only thing they appear to agree about is that nothing should be done, but they have a multitude of conflicting reasons why. Hmm…

The journalist, Richard Black, put together a top 10 list of sceptic arguments he gathered from emailing the 61 signers of a Canadian letter. While these aren’t any different in substance to the ones routinely debunked here (and here and here), this list comes with the imprimatur of Fred Singer – the godfather to the sceptic movement, and recent convert from the view that it’s been cooling since 1940 to the idea that global warming is now unstoppable. Thus these are the arguments (supposedly) that are the best that the contrarians have to put forward.

Alongside each of these talking points, is a counter-point from the mainstream (full disclosure, I helped Richard edit some of those). In truth though, I was a little disappointed at how lame their ‘top 10’ arguments were. In order, they are: false, a cherry pick, a red herring, false, false, false, a red herring, a red herring, false and a strawman. They even used the ‘grapes grew in medieval England’ meme that you’d think they’d have abandoned already given that more grapes are grown in England now than ever before (see here). Another commonplace untruth is the claim that water vapour is ‘98% of the greenhouse effect’ – it’s just not.

So why do the contrarians still use arguments that are blatantly false? I think the most obvious reason is that they are simply not interested (as a whole) in providing a coherent counter story. If science has one overriding principle, it is that you should adjust your thinking in the light of new information and discoveries – the contrarians continued use of old, tired and discredited arguments demonstrates their divorce from the scientific process more clearly than any densely argued rebuttal.

397 Responses to “BBC contrarian top 10”

  1. 201

    Anthony Hawes writes:

    [[But hang on – we can’t even relably model climate days ahead (often not the carpark). ]]

    You have weather confused with climate. Weather becomes chaotic quickly and can’t be accurately predicted more than a week or two in advance at most. Climate is a global or regional average of weather over a period of 30 years or more, and is basically deterministic. An example to illustrate the difference: I don’t know what the temperature will be tomorrow in Cairo, Egypt (weather). I can be fairly sure that it will be hotter than in Stockholm, Sweden (climate).

  2. 202
    Mike Sigman says:

    Given the NASA revelation in the last day or two that the Arctic warming is mainly a function of current variability, there are a lot of people with egg on their face at the moment. I’d like to ask the poster of #8 to think about the same question he posed for John Christy… what do you think about the Arctic melt now?

    [Response: Do you have a link? This is very unlikely to be true. – gavin]

  3. 203
    J.C.H. says:,2933,311884,00.html

    [Response: Typical. You are better off reading the real paper and press release. In them you will find no information about the ice changes – this study is purely concerned with ocean circulation differences – which do indeed have a strong decadal variability. The trend in sea ice however, does not. – gavin]

  4. 204
    Anthony Hawes says:

    There have been two posts (176. and 201.) criticising me regarding the difference between weather and climate – I understand fully the difference between the two. My point is that the level of complexity in weather is actually LESS THAN the level of complexity in the climate models, and furthermore our understanding of weather systems is BETTER THAN our understanding of the climate system. The argument is like that of economic modellers: that is, the day to day variability of the stock market is just noise, its the long term trends that are important – PROBLEM, the long term trends CANNOT be modelled. And I am sure (hope) the climate scientists here agree that climate is vastly more complex than the stock market. Any way – I hate analogies.

    By the way, it is a typical reaction that I get when I want to know more about the data link I posted ( – attack the man not the data (especially post 176.). The last 5 years certainly don’t support the projections from the models.

  5. 205
    Hank Roberts says:

    > certainly don’t support

    Have you informed the people there what you’re asserting based on those images? They ask you to let them “know when you use them and for what purposes” — they might even drop by and say whether they agree with your interpretation.

  6. 206
    John Mashey says:

    re: #204 Anthony
    The climate is constrained by the laws of physics, unlike the stock market, which occasionally at least breaks the law of gravity.

    You apparently don’t believe in laws of physics, or you think the economists have similar laws.

    Due to some modest operations research background, I was one of the people at SGI pushing (successfully, for a while, anyway) into economic modeling, Wall Street modelers, etc.

    I used to talk to them, just as I talked to climate modelers AND weather modelers.

    My experience does not accord with what you say, but maybe you have some relevant experience. If so, since you make strong statements, rather than asking questions, perhaps you can explain the basis for your assertions. I understood the domain difference between Keith’s and climate scientists’ models, but I don’t understand why you’re saying what you’re saying.

  7. 207
    J.C.H. says:

    “- PROBLEM, the long term trends CANNOT be modelled. …” – Anthony Hawes

    What are some examples of things you think are not understood about the climate system that would prevent climate models from making accurate predictions of long-term trends?

  8. 208
    Raplh Smythe says:

    Very interesting. Going from .03% of the atmosphere to .04% of the atmosphere, a trace gas that’s part of an incredibly complex, not totally well understood system, yanking it out because it looks correlated to the .7 C upward temperature anomaly trend and then attributing a cause/effect relationship to that. What about the IPCC’s land usage part of this, seems rather convenient to ignore it. Or the particulate aspect of fossil fuel usage. Even more odd is the fact that for the last 400K years the temperature has had +2 -8 C swings and oxygen18, sulfur, temperature, carbon dioxide and solar strength all move at once.

    Other than models that make assumptions, is there any other evidence that there is a cause/effect relationship between two of the variables in the system? That putting .01% more carbon dioxide into the atmosphere makes the asymmetric stretching and bending vibrational mode behaviors of it create a net .7 degrees of heat on a trend over a century+ (ignoring any lag) after removing everything else from the equation?

    Yes, I’m familiar with what ModelE says, but what else supports that? Please don’t mention melting ice or receding glaciers visually confirming it, that can be explained by particulates and ocean current and wind and the increased temperatures, just as particulates moderate the effects of other GHG and the weather patterns of the system. There seems to be a lot we don’t know in this equation, and it seems to jump to conclusions. Is making this conclusion now simply because it’s the best information we have, and we know how carbon dioxide acts well, and any explanation is better than none?

  9. 209
    Hank Roberts says:

    Raplh, are you the same person who posted this?

  10. 210
    David B. Benson says:

    Raplh Smythe (208) — Click on the link at the top of the page labeled Start Here. I also recommend the pages in the AIP Discovery of Global Warming site. The link is in the Science section of the sidebar.

    Reading these will anwer many of your questions.

  11. 211
    dean says:

    Re the response to 200:

    But to put the current rate in perspective, to say that that rate is well beyond what Nature can do herself is disingenuous. It most assuredly is not as can be clearly shown by looking at the data from 1910-1941. You must assuredly realize that the difference between the two rates over 100 years is a measly 0.3C (which I still maintain is statistically insignificant especially given the discrepancies between the GISS & HadCRUT3 datasets).

    Simply put, HadCRUT3 does not support the conclusion that the rate of rise in the current temperature data is greater than that which nature has done in the past.

  12. 212
    Steve Bloom says:

    Re #s 202/3: Gavin, I nailed Timo on this little misinterpretation back up in #154. With only a couple hundred comments in this thread so far, *surely* you didn’t forget? :)

    Note to Mike Sigman (#202): There are a fair number of people out there, Timo e.g., who have made a cottage industry out of misinterpreting climate science papers from a denialist POV. Such people frequently make claims about this or that important aspect of the science being challenged by the paper, but that pretty much always turns out not to be the case. More rarely you’ll get a scientist making a similar claim about their own paper, but generally they too turn out to be wrong (see e.g. the Stanhill paper discussed in the next thread). So if in future you see such a claim floating around out there, by all means feel free to ask about it, but try to ask rather than tell.

  13. 213
    David donovan says:

    Chris K and Dean

    It looks like what you are doing is determining the slope of a noisy signal by simply picking an somewhat arbitrary `low point’ and pairing that with a `high point’. This is not considered good practice even in 1st year physics labs ! IMHO your claims seem very silly.

  14. 214
    Raplh Smythe says:

    Hank, yes. The other post was about China mostly (and policy decisions involving them and others). Have I said anything that’s demonstratably incorrect? If so I will adjust. I believe that unless we can get both China and India to get on board, anything else is rather too little. Perhaps I’m just more pessimistic than I should be. I also think that it doesn’t matter what the details are; alternative fuels are good things if they don’t have unintended consequences. I think that’s where we should spend our time and energy rather than argue about proving an average of less than 1 ppmv per year causes less than .01 degree per year rise. Regardless of the relationship. And who isn’t for clean air and clean water?

    David, think as if you are grand poobah in charge of environmental policy for the US. You’re aware that the CO2 levels went from .03% to .04% and massive changes to our environment on the ground have been made, and that particulates in the air are cooling and on the ground are warming, and it’s been 125 years to get from there to here. You know that methane contributes, and that there’s some sort of cycle going on involving all these things interacting with clouds and water vapor and the heat/CO2 content of the oceans. You know the global mean anomaly has gone up .7 C over that time as a composite of land and sea sampling over time. You know that in the past, the variation’s been as big as 10 degrees and that the 5 major indicators all follow. In addition, most of the information is from models using assumptions about some of the more poorly understood variables in the system.

    Instead of getting something like that, they are told “CO2 levels are up 33% since the start of the industrial era and there is dangerous warming going on, and it’s accelerating.”

    Overstating the case is, I think, counterproductive. And how many pages long is AR4? I just think the focus is on the wrong things.

  15. 215
    Raplh Smythe says:

    BTW, I totally agree with gavin in the comment in #1: We know the models are imperfect, but unless we can define what it is we’re talking about, making blanket statements about the worth (or lack thereof) about the model is meaningless. We have to be more specific about what the issue is, and how it’s taken into account or not. Vague generalizations are meaningless, and the idea that we can throw out the model just because we don’t understand the function of x very well is disingenious to say the least.

  16. 216
    Ray Ladbury says:

    Ralph Smythe, That is the most astonishing mish-mash of misinformation (disinformation?) I’ve seen in awhile. Do you think that by throwing out words like “particulates” and mentioning a few random elements–all with no context–that you can gain some credibility here? Guess you were wrong. Look, if you want to learn about the science, you came to the right place, but try to figure out what it is that you don’t understand and ask questions. Don’t try to fool experts by blabbering CSI-style gibberish.

  17. 217
    James says:

    Re #204: [The argument is like that of economic modellers: that is, the day to day variability of the stock market is just noise, its the long term trends that are important – PROBLEM, the long term trends CANNOT be modelled.]

    Nonsense! I can give you a workable model of the stock market “climate” in one sentence: “In the long run, the stock market will increase in value about 7% per year, after inflation”. I could even give you a fairly amateurish explanation of why, if I felt like typing a few paragraphs.

  18. 218
    Ray Ladbury says:

    Keith, Twenty years ago, James Hansen predicted 20 years of warming. The subsequent 20 years have included the 13 warmest years in the past 125 years or so. That was a prediction. The probability of it occurring by chance is infinitesimal. The Mt. Pinatubo eruption was put into the models–no tweaking of parameters, no data fitting–and the models nailed it.
    Look, I work on radiation effects in semiconductors. When I test a 1 Gbit DRAM (as I just did), I am looking at only a few of the millions of state vectors in the state machine. If I wanted to test all of them, I would be testing for 15 years. I have to use modeling. Do I validate my results? You bet yer ass. But climate models are being validated continually.
    And in any case, the reality of anthropogenic climate change depends in no way on the models. All the models do is tell us the sensitivity will likely be 3 K per doubling and not 10 K per doubling. They are the only way we have to limit our estimate of the risk we face.
    Science works, Keith, and it works in more than just chemistry and physics. The scientific method can be applied in ways and to problems Galileo and Francis Bacon never dreamed of. Maybe you should learn how it works.

  19. 219
    Ray Ladbury says:

    Anthony Hawes said “PROBLEM, the long term trends CANNOT be modelled.”

    Gee, tell that to Warren Buffett–or hell to anybody who has been investing in their 401K. Anthony, the key to investing is not to look at the day-to-day variations (the weather), but rather at the average trends. And these CAN BE predicted and modeled. Can I tell you the temperature on Jan. 1, 2100. Of course not. Can I tell you that it is likely to be warmer than on Jan. 1, 2000. Yup! You are projecting your own ignorance onto the rest of the world–and climate scientists do not share it.

  20. 220

    #203 Fox news…. Really ? They have news????


    .04% hey? How about ozone? Knock all of .01% of it and what happens?

  21. 221
    John N-G says:

    #218 “The probability of [Hansen’s prediction verifying] by chance is infinitesimal.” Infinitesimal only if you assume annual global temperatures are white noise rather than red. I suspect the chances of a substantial 20-year warming trend at that point were somewhere around 1 in 10. Not infinitesimal, but still impressive. Someone with more time than I (Tamino?) should do the math.

    #179 I believe the “John” was John Mashey.

    [Response: John–actually this raises a number of interesting, and non-trivial considerations. If one uses the raw lag-one autocorrelation coefficient of the global mean surface temperature series (for hadcrut3 global mean 1850-2006, rho=0.87) one gets a decorrelation (e-folding) timescale of about 8 years, and a natural 20-year warming trend can arise quite readily given the red noise null hypothesis. However, the estimate of rho is arguably greatly inflated by the presence of long-term trends that are anthropogenically forced. In fact, if one compares the spectrum of global or hemispheric mean temperature with the spectrum of the best-fit AR(1) process, one finds that the low-frequency variability is far to great to be explained by an AR(1) null hypothesis. One way around this is to use a robust approach to fitting the AR(1) spectrum to the spectrum of the actual series. This yields a far smaller decorrelation timescales of about 1 year (see e.g. Mann and Lees, 1996), making a 20 year warming trend far more unlikely under the red noise null hypothesis. Yet another approach would be to use a coupled model forced by natural radiative forcing changes alone. Using a simulation of the NCAR CSM 1.4 coupled model forced by natural solar and volcanic radiative forcing (Ammann et al, 2006) over AD 850-1800, I get rho=0.6 (varies somewhat for any given 150 year period), which leads to an estimate of tau = 2 years, making a natural 20 year warming trend again unlikely. Someone w/ more time on their hands could calculate the probability distribution of 20 year warming trends based on the above alternative estimates of the noise decorrelation timescale. – mike]

  22. 222
    Laphroig says:

    Barton, Re 201

    This issue of weather/climate gets a bit irksome. My difficulty is that we simple do NOT have any direct experience of climate, what we actually, and only, experience is weather, and we do that in the eternal “now” of consciousness. Weather is “real”, climate is an abstraction, based on memory (terribly spotty, and often downright creative). Of course we add various systems that attempt to augment memory by inserting some sort of “objective” devices (thermometers) or systems (record keeping and adjustments) to counter the pure subjectivity of sense experience. And those abstractions are far simpler than the reality of the experience of weather. They basically consist of temp, wind and humidity. What about all the little variables like, how old you are, what you’re doing, and with whom, when you last ate, what you drank the night before, what you’re wearing etc. If it gets a little warm, it’s also a whole easier to adjust a few of these than, say, change the climate.

    Now, as a set up for a question, a few months ago we (family members) performed a little experiment. At a point on the highway 2 about 15-20 minutes from the southern outskirts of Edmonton we had friends park at the side of the road to wait till they received our phone call when we got about 10 blocks into city. When we separated both of our car outside temperature readings were the same. When we phoned them our temp reading was four degrees warmer, whereas theirs remained constant. So direct experience tells me that within about 20 miles (on basically flat prairie, and with no obvious weather changes), there was a significant change in temperature between two close points in the same time.

    Discounting the UHI issue here is my question. In an anything-is-possible world what size would the grids have to be so that the earth’s temperature would be based on the whole earth, i.e. that the temperature in any one grid would vary no more than, say a degree from its adjacent grids? If memory serves (and that’s a stretch) a really accurate survey could probably be made with a sample of 12 to 15 hundred, but would also require that each of these world wide grids would have an equal chance of selection and all would be selected by chance.

    Then to get over the quibbling about things like min/max etc., maybe we do this on an hourly basis, changing half the sample each hour, for a year or so ( a sort of tempersherry—eecchhh!).

    Now I realize that this way of monitoring of the earth’s real temperature may be a bit gold platted, but on a scale of 1 to 10 (10 being this one) what score would you give to those that are being used today?

    Thank you.

  23. 223
    Ellis says:

    CW-Gavin was clearly not engaging in a Straw-Man argument.
    Hothouse – Snowball is the natural range of the Pharenozoic. In order to support your argument you must specify what bounds of natural variability you are referring to. So as you seem not to prefer the bounding Gavin points out, perhaps you could define what you see as “the bounds of natural variability”.

    First, Gavins’ bounds of natural variability is not the straw man. His, “your argument is equivalent to saying that nothing less dramatic than the freezing over of the oceans or the raising of the temperature by 10 deg C or so can possibly be attributed to any forcing.” is a perfectly constructed straw man, completed with the conclusion that my point is absurd. I am not even sure if it is possible to disprove natural variability with extremes of natural variability, but, if it will make you feel better when I wrote the comment I was refering to the Holocene.

    CW- You state (with respect to orbital forcings, giant volcanoes, asteroids, Heinrich events etc) that: “I am not sure that it follows that none of them are relevent today.” If you are not sure then it implies that you have reason, thus you should be able to detail such reason in terms of mechanism and evidence…
    In other words – please do so.

    I am not sure that it follows is a nice way of saying you are wrong. The rest of what I wrote, “Our climate is defined by the orbital forcings, however, I understand your point that these forcings change little on centennial time scales.” I believe makes clear that I was able to infer Gavins’ meaning. For further reading about the mechanics that are the overriding facets of the climate system please see

    CW-You state: “The theory of AGW rests only on one principle, as far as I can tell, that the warmth of the past century is outside the bounds of natural variability.”
    AGW clearly does not rely upon the current warming being outside the bounds of Holocene variance.

    Technically, you are correct AGW can exsist within the boundries of Holocene variability. However, as you state, “What matters is whether atmospheric CO2 levels can be driven high enough to attain that state in the future.” Thus, eclipsing natural variability, and if you really believe that the argument for AGW is not being driven by the departure from the normal, then I humbly suggest that you are not following the story.

    CW-Then you take Gavin’s clear analogy and attempt to dismiss by taking it literally. Which whilst worth noting is unworthy of comment.

    “Just because large forest fires have occurred naturally in the past, does that imply that arson cannot happen?” Is not an analogy, it is a non sequitur, and my sarcasm is an appropriate response. Perhaps you were refering to the next line from Gavin,” Or that if we see someone walking away from a fire with an empty kerosene can and some matches, we can’t logically infer that he may have had something to do with it?”
    To which I responded, “I don’t object to the claim that a dissproved alternate theories bolsters your stance, I do object when this is taken as proof of your theory.”
    Is this not reasonable?

    CW-You state,”We have warming, backed up not only by a range of different measuring techniques – from boreholes to satellite thermal emission from the atmosphere, but also by the global average trend in water vapour changes. The increase in ocean heat content shows that the warming is significant.”

    Now it is your turn, please direct me to water vapor trends and ocean temperature trends. Also, the expression we have warming is meaningless without a starting point, for the holocene we are actually cooling.

    CW-We have concomitant observations that are expected with CO2 (diurnal range, vertical profile of changes – stratospheric cooling, tropospheric warming).

    Is the stratosphere cooling because of CO2? This graph shows very strong correlation between observed cooling and total ozone.
    Perhaps, you could direct me to the graph of stratospheric CO2 content versus observed temperatures and we can compare and contrast?

    CW-To dismiss CO2 you have to address this pattern. If CO2 isn’t to blame, what is causing the warming and the observations I outline? The stance “It must be anything but CO2″ does not constitute a theory.

    Excellent, now you can set up a straw man just like a bona fide climate scientists.

  24. 224
    Roger Coppock says:

    Why do fossil fools tell obvious lies? The strategy is to provide
    static. You’ll see the same strategy from the local baseball fans
    when the opposing team is at bat. Constant senseless banter
    prevents an opponent from concentrating. “Hay batter, hay batter,
    batter, batter, SWING,” replaced by, “Mediaeval warm period,
    cooling since 1998, computer models . . .”

    Note that these lies live in their own underworld. You don’t see
    the fossil fuel industry using them to defend themselves from
    environmental lawsuits. You won’t see these obvious lies from
    US major party presidential candidates, regardless of how much
    money the industry has contributed to their election campaigns.
    In both venues, facts are carefully checked and there are
    penalties for telling obvious lies.

  25. 225
    Jim Eager says:

    Re Anthony Hawes @ 204: “There have been two posts (176. and 201.) criticising me regarding the difference between weather and climate – I understand fully the difference between the two.”

    Yet you still wrote “we can’t even relably model climate days ahead,” a favorite rhetorical throw-away of AGW “skeptics” and outright denialists.


  26. 226

    Ralph Smythe writes:

    [[Going from .03% of the atmosphere to .04% of the atmosphere, a trace gas that’s part of an incredibly complex, not totally well understood system, yanking it out because it looks correlated to the .7 C upward temperature anomaly trend and then attributing a cause/effect relationship to that.]]

    You are misunderstanding something fairly basic here. The greenhouse effect does not depend on an observed correlation. It is a matter of radiation physics. If you put more of a greenhouse gas in a planet’s surface, then the surface must become hotter, unless some countervailing process is blocking it. The theory of global warming depends on radiation physics, not on observations of climate.

  27. 227
    dean says:

    Re: 213

    David, actually I did as I was asked to do by Marcus (see #144), namely do a 5 and 10 year average of the data rather than a single point. I did not just take a low and high point and run with it.

    I looked at the results and I just came to a completely different conclusion than the rest of this community. Namely, than when using the HadCRUT3 data, the temperature change we’re seeing isn’t outside the natural variation as had been claimed.

    Instead of just saying i don’t know what i’m doing, why not look at the numbers I’ve posted and figure out how i’m misinterpreting things. In doing so, I challenge you to explain how the differences between datasets is immaterial when delta between datasets is significantly larger than the delta I’ve documented.

  28. 228
    John N-G says:

    #221 Mike, thanks for the detailed response. “…raises a number of interesting, and non-trivial considerations” Does it ever, and I did not acknowledge that complexity in my first comment.

    Your answer is colored by a signal detection background, while mine is colored by experience with forecast verification.

    First off, we must define the a priori knowledge and a “no-skill” forecast. If the “robust” estimate of the red-noise spectrum is used, the success of the forecast is no more than a demonstration that low frequency and/or secular signals are present, i.e. signal detection. But the successful Hansen forecast is intended to stand for something much stronger: that the significant very low frequency and quasi-secular signals are predictable (using a physical model with appropriate forcings). In that context, the forecast must be verified against the assumption that the very low frequency and quasi-secular signals are unpredictable, that is, part of the red noise spectrum. Thus it seems to me that the raw lag-one autocorrelation is more appropriate here for determining the skillfulness of the forecast.

    (There’s probably a good journal article to be written about this, if you want to discuss it offline.)

    [Response: Sure thing John, would be very happy to discuss this further offline :) – mike]

  29. 229
    Hank Roberts says:

    Google: hadcrut3 stoat

    William has posted several times about taking averages from this data set; the CA folks have been arguing about his postings a lot lately.
    That may be spilling over into this thread, just guessing.

    This thread from Nature may help (albeit it’s well seasoned with, um, various uniquely personal theories in the comments).

  30. 230
    Jim Eager says:

    Re Raplh Smythe@ 2008: “Very interesting. Going from .03% of the atmosphere to .04% of the atmosphere, a trace gas that’s part of an incredibly complex, not totally well understood system, yanking it out because it looks correlated to the .7 C upward temperature anomaly trend and then attributing a cause/effect relationship to that.”

    What’s interesting is that you choose to describe atmospheric CO2 as a mere “trace gas” comprising only .03% to .04% of the total atmosphere, a favoured rhetorical tactic employed by “skeptics” and out right denialists in an attempt to minimise the role of CO2 specifically and of greenhouse gasses in general.

    By this measure water vapor, which varies as a proportion of the atmosphere depending on temperature and altitude, comprises a high of around 4%. Methane (CH4), the third most common greenhouse gas, constitutes a miniscule .00017% of the atmosphere, while nitrous oxide (N2O) stands at .00003%. Man-made chloroflourocarbons (CFCs) and a host of other trace gases comprise slightly less at around .000025%, and ozone (O3) is even smaller at .000004%. In other words, all greenhouse gases combined comprise only 4.040229% of the atmosphere.

    Yet these gasses are responsible for warming Earth’s surface and lowest portion of the atmosphere by around 33°C, which is clearly all out of proportion to their percentage of the atmosphere. It’s therefore far more instructive to describe CO2 in terms of the greenhouse effect it accounts for and how important its increase is, as opposed to its percentage of the total atmosphere.

    H2O makes up the largest portion of total greenhouses gasses by far, accounting for between 36% and 66%* of the greenhouse effect, but It can only increase in the atmosphere as temperature increases–any excess simply precipitates out as rain, snow or ice within days.

    CO2 is second, accounting for between 9% and 26%* of the greenhouse effect. it is relatively long-lived in the atmosphere (50-200 years or more), and since 1750 (the pre-industrial era) atmospheric CO2 has increased by nearly 38% and is still rising rapidly, almost entirely due to anthropogenic causes (burning of fossil carbon fuels, cement production, land use changes), slowing of natural carbon sinks as they approach saturation, and emission from frozen soils as they thaw.

    CH4 is third, accounting for 4-9% of the greenhouse effect. Methane, which is ~21 times as powerful a greenhouse gas as CO2, is relatively short-lived in the atmosphere (~12 years), yet it has increased by 152% since 1750, also mostly due to anthropogenic causes (agriculture, animal husbandry, coal, oil and gas extraction), plus, it breaks down into CO2 in the atmosphere, so its carbon continues to be part of a greenhouse gas.

    O3 accounts for 3-7%. Tropospheric O3 has increased due to anthropogenic emissions, but stratospheric O3 has decreased due to CFCs and HCFCs.

    N2O only accounts for around 1.3-3%, but it is ~310 time more powerful than CO2 and relatively long lived (120 years). It has risen by 18% since 1750.

    CFCs, which did not exist before mid-C20, are an entirely new addition. They are 5000 to 14000 time more powerful than CO2. Fortunately they really are trace gasses.

    *The reason for the large range is the overlap in wavelenghts that H2O and CO2 absorb.

    So, the next time someone tries to assert that CO2 is only a harmless “trace” gas, keep all this in mind.

  31. 231
    David B. Benson says:

    Raplh Smythe (214) — As there are several Davids here, I don’t know whether your remark was directed to me or not. Since you fairly clearly didn’t do the assigned reading, :-) I’ll respond just to

    Instead of getting something like that, they are told “CO2 levels are up 33% since the start of the industrial era and there is dangerous warming going on, and it’s accelerating.”

    CO2 is now 385 ppm, was 280 ppm, so I hope the correct ratio, 1.375, is communicated. This results in a radiative forcing of about 1.5 W/m^2 and it is dangerous, particularly to marine organisms. It is accelerating in that the CO2 concentration now goes up about 2 ppm per year, as opposed to about 1 ppm per year in the 1990s.

    To illustrate the magnitude of just the CO2 problem, about half of the total radiative forcing, it is estimated that humans have added about 500 billion tonnes (Gt) of carbon to the active carbon cycle by burning fossil fuels and net deforestration. Bringing the radiative forcing due to CO2 down to the level experienced in 1950 (1/2 of today’s) requires permanently sequestering about 350 Gt as well as eliminating or sequestering the yearly addition of about 8.4 Gt. If accomplished, the net radiative forcing would be about 3/4 of the current value, still substantial.

  32. 232
    CobblyWorlds says:

    “if you really believe that the argument for AGW is not being driven by the departure from the normal, then I humbly suggest that you are not following the story.”
    Of course we’ll leave the bounds of Holocene variability, just give us a chance. We’ve only got round to using under 10% of the extractable reserves of fossil fuels. And we have a warming commitment for what we’ve done so far. That said I’m glad we at least now agree that whether things are out of natural variability (specifically holocene) is not critical to the science. And with regards the “story” – I just read the science.

    Milankovitch cycles.
    These are demonstrably not causing the current warming. Sorry, I use that wiki page as an aide memoire – no news for me there.
    The actual changes in forcing (typically given at 65degNorth) due to precessional components are small and happen way too slow e.g. Roe “Indefence of Milankovitch” pdf – note figure 2. The actual lattitudinal insolation changes are amplified by changes such as ice sheet response causing albedo change as a positive feedback.
    In Hansen et al “Trace Gasses and climate Change” figure 3 demonstrates that you need to include GHGs to get close to the temperature variations observed in the ice-ages.

    “Just because large forest fires have occurred naturally in the past, does that imply that arson cannot happen?” – Gavin
    Could be translated as:
    Just because natural factors have caused changes in the past, that does not mean that the changes we see today cannot be due to humans.
    Surely you don’t think that’s a non-sequitur?

    Temperature trends etc.
    I’m so tempted to refer you to google (I’ve been used as a contrarist fact-gopher before). ;)
    But as you ask so nicely:
    Oceans – I recomend the Levitus et al study of ocean temperatures and heat content – Warming of the World Ocean, 1955-2003. Available from the 2005 collection on this page:
    Humidity – only got a paper version – Met Office UK work has shown little/no(?) change in relative humidity but an increase in specific humidity. The point is that’s an expected signature of warming. i.e. it really is warming.
    3 main surface datasets. See my post 82 above for graphs.
    And here from the Met Office is the LoStrato/Tropo/Surface compared:

    Statospheric ozone.
    The graph you linked to is from this page:
    The legend for that graph clearly states it is for the Arctic.
    Ozone levels are higher at the poles: (4.2 Distribution of Ozone by Season and Location) Because there’s more ozone in the Arctic than at lower latitudes it does not surprise me that there’s a close correlation between it’s loss rate and temperature. But on this page: you’ll see a study of the contribution of O3 and greenhouse effect cooling by GFDL.
    The mesosphere is cooling – ozone is not a significant factor there. But a reduction in outgoing longwave flux due to the enhanced greenhouse effect can cause such a cooling. There’s a plain-english rundown here:
    So yes, there is a contribution from O3, but the greenhouse effect also has a substantial contribution. By the way, CO2 doesn’t have an impact on the stratospheric trends by virtue of it’s presence in the Stratosphere. Most of the enhanced greenhouse effect is seen within the low-mid troposphere. Strato cooling by ozone is due to reduced absorption of UV with less ozone. Strato cooling by GHGs is due to a reduction in the net upwards flux of IR. Increased solar radiation would imply a warming of all levels of the atmosphere.

    And finally, to dimiss CO2 you really DO have to address the phenomena it explains, I am not being difficult here. It’s impossible to prove absolutely that a theory is correct. The work in considering a theory hangs upon attempts to refute it – stacks of that has been done in primary peer-reviewed science – and the theory of the enhanced greenhouse effect is stronger for it.

  33. 233
    Keith says:

    John Mashey.

    Thank you, thank you, thank you. I have just that light bulb moment where for the first time somebody has actually give me an explanation that makes sense rather than just shouting at the top of their voices. Yes, John, that’s exactly right, we do need what is in effect a binary result. Your explanation of why climate models are in less need of such definitive, absolute results makes things much clearer. I can see how over time a model might evolve but still give the same overall result. I won’t say that I understand fully why that is; I’d need to do a lot more reading round the subject, but it makes sense. Perhaps it’s the difference between accuracy and precision. Anyway, thank you. I have a MUCH better feel to what is being discussed and why the fields are more different than I’d imagined. Superb. A great explanation. Thanks mate!

  34. 234
    Theo H says:

    I’m a real layman when it comes to all this on computer modeling.

    OK, so a _very_ simple question. If computer modeling is not to be the way future climate is to be predicted, what is/are the alternatives?

    Theo Hopkins.

    (Or should the UK’s Met Office Chief Scientist, who lives just round the corner from me, tap on the glass of a barometer as he settles at his desk each morning?)

  35. 235
    David B. Benson says:

    My comment #231 — Oops! Wrong arithmetic. Removing that much carbon from the active carbon cycle gets the CO2 radiative forcing down to about 1/3 of today’s value, for a total radiative forcing of about 2/3 of today’s value.

    Theo H (234) — Why not use computer modeling to predict future climate?

  36. 236
    gringo says:

    Among the many vague “cooling is coming” statements I found on the Net there is this:
    ” I still think, personally, that once the ocean’s deep water currents change, that we will see a cold trend, (after the heat up).”

    I’m not a scientist and I don’t know anything about the link between global mean temperature and ocean currents. What do you think this guy was talking about?
    Does the IPCC take this possibility into account or this is just more BS from contrarians?

  37. 237
    Ray Ladbury says:

    Gringo, Well… first, I’d like to ask why your correspondent thinks the deep-water currents will change…and why it is more likely that the change will increase cooling, rather than warming. I know of no reason to expect either. The whole thing sounds like a Cubs fan saying “Wait ’til next year…”
    It is true that the deep oceans represent a huge heat reservoir, and if you started having a large amount of overturn of cold water to the surface, it could cool things off for awhile. However, what happens when the warm surface water starts warming the deep oceans? You might start getting clathrates sublimating, increasing methane in the atmosphere, and that would warm things up again really fast. Your correspondent would seem to be involved in the time-honored activity we call wishful thinking.

  38. 238
    gringo says:


    As it usually happens, he didn’t explain why he thinks what he thinks. But isn’t this view similar to that of William Gray?
    And since 2006 was just the sixth warmest year on record and 2007 will also be cooler than several previous years ( I guess due to La Nina as the Jan-Apr period was warmest on record according to NOAA) don’t you think the contrarians will use this as evidence that some natural factor now overwhelms GHG forcing?

  39. 239
    Concerned of Berkeley says:

    Have you guys addressed this paper yet?

    “Falsification Of The Atmospheric CO2 Greenhouse Effects Within The Frame Of Physics
    Version 3.0 (September 9, 2007)” by
    Gerhard Gerlich and Ralf D. Tscheuschner

    [Response: Some links here: – It’s garbage. – gavin]

  40. 240
    Chuck Booth says:

    Re # 222 Laphroig: “we actually, and only, experience is weather, and we do that in the eternal “now” of consciousness. Weather is “real”, climate is an abstraction, based on memory (terribly spotty, and often downright creative).”

    By that logic, anything that happened more than a fraction of second ago, such as our “experience” with this morning’s weather, is based on memory (terribly spotty, and often downright creative). Fortunately, people have been keeping detailed records of temperature, humidity, barometric pressure, rainfall, the times of germination and flowering of plants, the geographical distribution of plants and animals, the departure and return of migrating birds, etc, at many locations for a long time, in some cases for centuries. Plus, there are slow-growing animals and plants whose tissues record average growth conditions at fixed locations over decades or centuries; together with modern weather recording networks on land, in the ocean, and in the atmosphere, these data allow climatalogists to generate detailed records of climate at diverse geographical locations on the planet, and to account for geographical variations, such as urban heat islands, when estimating mean values for a region or the entire globe.

  41. 241
    Rod B says:

    Gavin, re your response to 203: What did the NASA press release mean, then, by “…The results suggest not all the large changes seen in Arctic climate in recent years are a result of long-term trends associated with global warming.” ?

    [Response: Exactly what it says. The ocean circulation changes have a significant decadal variability, but the sea ice shows a much stronger trend that is likely tied to GW. – gavin]

  42. 242
    Lawrence Coleman says:

    If you were watching An Inconveneint truth al Gore mentions that in eons past the great lakes are remmenants of a huge inland fresh water sea that broke the banks on the Nova Scotia side of Canada, trillions of gallons of fresh water was released into the ocean, effectively stopping the Great ocean conveyor, this had the effect of plunging huge parts of the nothern hemisphere into a snap ice age that lasted a thousand years or more. The area east of nova scotia is where the sea is saltier and thus more dense and begins sinking and moving south at the bottom of the atlantic whilst the less salty ocean currents run over the top heading north just west of ireland. When this massive flood of fresh water diluted the saltier water about to head south it jammed the conveyor and in as little as ten or so years europe and north america was plunged deeply into a severe ice age. Now what do expect happens when the increasing ice melt from greenland enters the ocean?? No-one knows! It could trigger the conveyor to slowdown or stop completely. My guess is that it wont stop since the ice melt is happing at a slower pace than the sudden surge from americas great lakes region.

  43. 243
    Lawrence Coleman says:

    f you took measurments many thousands of years back you will see cyclical changes in the ice shhet thickness and area, but are small ripples when you compare them with the disturbng trend seen now… a 23% reduction in area in two short years. We are no in a situation where positive feedback loops are heterdyning on other positive feedback loops causing dramatic instability.

  44. 244
    Hank Roberts says:

    > he didn’t explain why he thinks what he thinks

    I searched out the one page where you found that belief about ocean currents. I’d suggest starting somewhere else.*

    “Start Here” link at top of page; Science links in right side.

    * Remember, this is the Web, not Usenet (“the way to get good information on the Usenet is to post what you think and await correction”). On the Web, anybody and everybody’s got more opinions than you can shake a stick at, and few people try to teach.

  45. 245
    Lawrence Coleman says:

    But to be a devils advocate to my own question over whether the ice melt from greenland will cause the ocean conveyor to change it’s ways is this point; With less and less ice covering the north polar region the sea gets warmer and less the ocean current coming north past the west coast of europe and ireland will have less cooling thus less salt concentration and thus less sinking…so the ocean conveyor could well stop altogether but over decades I think, not suddenly. What will probably happen soon if it’s not happening already is that the speed of the conveyor will gradually slow down…so one major canary in a coalmine..will be if we see an accelleration in the retardation of speed of this deep ocean current..time to get very sweaty palms and forhead.

  46. 246
    gringo says:


    Ok but what about 2006 and 2007 being cooler than several previous years?
    Moreover the UK Met office recently predicted that
    “temperatures will stall because of natural climate effects that have seen the Southern Ocean and tropical Pacific cool over the past couple of years.”

    “The forecast from researchers at the Met Office’s Hadley Centre in Exeter reveals that natural shifts in climate will cancel out warming produced by greenhouse gas emissions and other human activity until 2009”

    It’s not too hard to predict what the denial camp will do if there won’t be record breaking year until 2010.

    And just what are these “natural climate effects” which have cooled the Southern Ocean and tropical Pacific?

  47. 247
    Øyvind says:

    People keep referring to scientific consensus as it was the same as the Conclave reaching a consensus of the new Pope before sending out white smoke, or that me and my buddies reach a consensus of leaving the pub due to intoxication and a common realization that we must get up for work the next morning.

    Well, the layman definition of consensus may include these examples. In science it is rather less democratic. A theory reaches consensus by constantly being evaluated for its success-rate. Consensus may be reached when a high-level theory successfully explain a matrix of lower-level theory-structures. The greenhouse gas (GHG) theory is such a theory (in reality the top-level theory that IPCC has as consensus should probably be denoted ‘theory of climate change’ or something similar, however I will keep GHG here). The GHG-theory allows theories from i.e. physics, chemistry, biology and geology to interact inside one coherent understanding at the same time while sustaining all fundamental scientific laws (i.e. gravity, radiation, friction etc). If a branch of science identify an area where the global warming theory yield conflicting or even impossible consequences, the theory of GHG is regarded under attack. However, such inconsistencies are not enough to falsify the theory. The continued success of the theory in other and more substantial areas safe-guard the theory, while studies are carried out to try to resolve the mismatch or a new and better top-level theory (the sun-volcano alone theory?) start to explain the different science branches and data-matrix. This is what commonly is known as ‘normal science’.

    What does this philosophical reflection do under this post? I think that BBC and Gavin’s post fundamentally explain why there is such a strong consensus of the GHG-theory. There simply exists no over-arching consistent theory that can do what the GHG-theory enables in terms of revealing insight and explanation of such a wide web of sub-disciplinary theories, hypotheses and data. As long as the ‘sceptics’ keep throwing around stand-alone hypothesis (often without publishing them) there simply exists no alternative. A scientific theory must explain a large subset of inter-woven sub-theories and hypotheses. This is the largest challenge for the sceptic community: Join all the bits and pieces together into a coherent theoretical alternative. And remember, this new theory can not only explain the last 100 years, it must shed equal insight on glacial climate, the Tertiary warmth (i.e. it must be general). The theory must thus be time-independent. The theory must furthermore give predications that can be tested while acknowledging all scientific laws etc etc. This is the only scientific approach – and one that every “consensus-scientist” follows every day by critically gaining data, developing theoretical consequences and creating, testing and refuting hypotheses.

    I believe this may illustrate the difference between the scientific consensus that IPCC represent and the sceptical alternative. In the first case consensus is reached by scientists from different disciplines acknowledging that their respective theories and data are best (not perfectly!) explained by the GHG over-arching and constantly evolving theory (biologists have consensus regarding evolution as their top-level evolving theory). That for example 19 000 sign some petition is “hand-raising consensus” where any individual may have any of multiple (and conflicting/inconsistent) reasons to sign. This does not, however, provide coherent scientific insight or explanation and is thus scientifically valueless.

  48. 248
    Anthony says:

    I have a few questions:

    1. Will the increase in water vapour caused by AGW expected to result in an increase in cloud cover?
    2. To what extent do the current models used by the IPCC factor in the albedo effect of clouds. I realise they are part of the models, but do the models allow for a change in cloud cover similar to the way they allow for changes in snow cover.
    3. Is there a definitive source (preferable a paper) on changes in global cloud cover in the last few decades?
    4. This is a bit of a supplementary question that has been on my mind over the last 6 months: The models didn’t predict the current non-warming (and likely cooling this year – la Nina?) back in 2002. I realise they aren’t (weren’t) capable of showing short term variations, but as mentioned in post 246. the Hadley Centre seems to be able to predict changes at a much higher resolution – only 4 years. Does this Hadley model show the 6 year plateau we have just experienced and if so, to what was the cause attributed?

    I look forward to your replies.

  49. 249
    Ray Ladbury says:

    Gringo, Oh they will certainly argue that way–just as they take every cooling after an El Nino year to mean the end of the warming epoch. But denialists are not evidence based–they will find ways of arguing their position in contravention of the evidence no matter what. As the history of quantum theory shows, when people adopt unreasonable positions–even people as brilliant as Einstein–science marches around them. You have to go with the preponderance of evidence.

  50. 250
    Dan W says:

    Lawrence Coleman (#242, 243),

    The IPCC agrees with you.