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The global cooling myth

Filed under: — group @ 14 January 2005 - (Français)

Every now and again, the myth that “we shouldn’t believe global warming predictions now, because in the 1970’s they were predicting an ice age and/or cooling” surfaces. Recently, George Will mentioned it in his column (see Will-full ignorance) and the egregious Crichton manages to say “in the 1970’s all the climate scientists believed an ice age was coming” (see Michael Crichton’s State of Confusion ). You can find it in various other places too [here, mildly here, etc]. But its not an argument used by respectable and knowledgeable skeptics, because it crumbles under analysis. That doesn’t stop it repeatedly cropping up in newsgroups though.

I should clarify that I’m talking about predictions in the scientific press. There were some regrettable things published in the popular press (e.g. Newsweek; though National Geographic did better). But we’re only responsible for the scientific press. If you want to look at an analysis of various papers that mention the subject, then try

Where does the myth come from? Naturally enough, there is a kernel of truth behind it all. Firstly, there was a trend of cooling from the 40’s to the 70’s (although that needs to be qualified, as hemispheric or global temperature datasets were only just beginning to be assembled then). But people were well aware that extrapolating such a short trend was a mistake (Mason, 1976) . Secondly, it was becoming clear that ice ages followed a regular pattern and that interglacials (such as we are now in) were much shorter that the full glacial periods in between. Somehow this seems to have morphed (perhaps more in the popular mind than elsewhere) into the idea that the next ice age was predicatable and imminent. Thirdly, there were concerns about the relative magnitudes of aerosol forcing (cooling) and CO2 forcing (warming), although this latter strand seems to have been short lived.

The state of the science at the time (say, the mid 1970’s), based on reading the papers is, in summary: “…we do not have a good quantitative understanding of our climate machine and what determines its course. Without the fundamental understanding, it does not seem possible to predict climate…” (which is taken directly from NAS, 1975). In a bit more detail, people were aware of various forcing mechanisms – the ice age cycle; CO2 warming; aerosol cooling – but didn’t know which would be dominant in the near future. By the end of the 1970’s, though, it had become clear that CO2 warming would probably be dominant; that conclusion has subsequently strengthened.

George Will asserts that Science magazine (Dec. 10, 1976) warned about “extensive Northern Hemisphere glaciation.”. The quote is from Hays et al. But the quote is taken grossly out of context. Here, in full, is the small section dealing with prediction:

Future climate. Having presented evidence that major changes in past climate were associated with variations in the geometry of the earth’s orbit, we should be able to predict the trend of future climate. Such forecasts must be qualified in two ways. First, they apply only to the natural component of future climatic trends – and not to anthropogenic effects such as those due to the burning of fossil fuels. Second, they describe only the long-term trends, because they are linked to orbital variations with periods of 20,000 years and longer. Climatic oscillations at higher frequencies are not predicted.

One approach to forecasting the natural long-term climate trend is to estimate the time constants of response necessary to explain the observed phase relationships between orbital variation and climatic change, and then to use those time constants in the exponential-response model. When such a model is applied to Vernekar’s (39) astronomical projections, the results indicate that the long-term trend over the next 20,000 years is towards extensive Northern Hemisphere glaciation and cooler climate (80).

The point about timescales is worth noticing: predicting an ice age (even in the absence of human forcing) is almost impossible within a timescale that you could call “imminent” (perhaps a century: comparable to the scales typically used in global warming projections) because ice ages are slow, when caused by orbital forcing type mechanisms.

Will also quotes “a full-blown 10,000-year ice age” (Science, March 1, 1975). The quote is accurate, but the source isn’t. The piece isn’t from “Science”; it’s from “Science News”. There is a major difference: Science is (jointly with Nature) the most prestigous journal for natural science; Science News is not a peer-reviewed journal at all, though it is still respectable. In this case, its process went a bit wrong: the desire for a good story overwhelmed its reading of the NAS report which was presumably too boring to present directly.

The Hays paper above is the most notable example of the “ice age” strand. Indeed, its a very important paper in the history of climate, linking observed cycles in ocean sediment cores to orbital forcing periodicities. Of the other strand, aerosol cooling, Rasool and Schneider, Science, July 1971, p 138, “Atmospheric Carbon Dioxide and Aerosols: Effects of Large Increases on Global Climate” is the best exemplar. This contains the quote that quadrupling aerosols could decrease the mean surface temperature (of Earth) by as much as 3.5 degrees K. If sustained over a period of several years, such a temperature decrease could be sufficient to trigger an ice age!. But even this paper qualifies its predictions (whether or not aerosols would so increase was unknown) and speculates that nuclear power may have largely replaced fossil fuels as a means of energy production (thereby, presumably, removing the aerosol problem). There are, incidentally, other scientific problems with the paper: notably that the model used was only suitable for small perturbations but the results are for rather large perturbations; and that the estimate of CO2 sensitivity was too low by a factor of about 3.

Probably the best summary of the time was the 1975 NAS/NRC report. This is a serious sober assessment of what was known at the time, and their conclusion was that they didn’t know enough to make predictions. From the “Summary of principal conclusions and recommendations”, we find that they said we should:

  1. Establish National climatic research program
  2. Establish Climatic data analysis program, and new facilities, and studies of impact of climate on man
  3. Develope Climatic index monitoring program
  4. Establish Climatic modelling and applications program, and exploration of possible future climates using coupled GCMs
  5. Adoption and development of International climatic research program
  6. Development of International Palaeoclimatic data network

Which is to say, they recommended more research, not action. Which was entirely appropriate to the state of the science at the time. In the last 30 years, of course, enormous progress has been made in the field of climate science.

Most of this post has been about the science of 30 years ago. From the point of view of todays science, and with extra data available:

  1. The cooling trend from the 40’s to the 70’s now looks more like a slight interruption of an upward trend (e.g. here). It turns out that the northern hemisphere cooling was larger than the southern (consistent with the nowadays accepted interpreation that the cooling was largely caused by sulphate aerosols); at first, only NH records were available.
  2. Sulphate aerosols have not increased as much as once feared (partly through efforts to combat acid rain); CO2 forcing is greater. Indeed IPCC projections of future temperature inceases went up from the 1995 SAR to the 2001 TAR because estimates of future sulphate aerosol levels were lowered (SPM).
  3. Interpretations of future changes in the Earth’s orbit have changed somewhat. It now seems likely (Loutre and Berger, Climatic Change, 46: (1-2) 61-90 2000) that the current interglacial, based purely on natural forcing, would last for an exceptionally long time: perhaps 50,000 years.

Finally, its clear that there were concerns, perhaps quite strong, in the minds of a number of scientists of the time. And yet, the papers of the time present a clear consensus that future climate change could not be predicted with the knowledge then available. Apparently, the peer review and editing process involved in scientific publication was sufficient to provide a sober view. This episode shows the scientific press in a very good light; and a clear contrast to the lack of any such process in the popular press, then and now.

Further Reading:

Imbrie & Imbrie “Ice Ages: solving the mystery” (1979) is an interesting general book on the discovery of the ice ages and their mechanisms; chapter 16 deals with “The coming ice age”.

Spencer Weart’s History of Global Warming has a chapter on Past Cycles: Ice Age Speculations.

An analysis of various papers that mention the subject is at

47 Responses to “The global cooling myth”

  1. 1
    Pat Neuman says:

    Why has there been a lack of ‘process’ in the popular press,
    then and now? … especially in the U.S.

    I think U.S. government agency administrators, directors and managers are reluctant to make waves.

  2. 2
    Tony Weddle says:

    There was a recent Horizon programme on television in the UK. It concerned a phenomenon labelled “global dimming”. Some of the precursors of this are mentioned in the article above. However, more work has been done recently and it’s potentially scary stuff. Around the world, the amount of sunlight reaching the earth has dropped by between 10% and a staggering 22%, since the 1950s. The results of research into measuring the effect have largely been ignored by the scientific community until recently.

    Global dimming has, apparently been lessening the effects of global wraming. The scary thing is that our attempts to clean up the microscopic particles that we emit in burning fossil fuels (for health reasons) could drastically cut down the global dimming effect, allowing global warming to race off. Some estimates suggest that the point of no return is only 25 years away.

    I’ve been trying to find scientific articles on the subject, but recent ones have eluded me so far. Here is a link to the transcript of the programme:

    [Response: The horizon programme perhaps overestimates the degree of knowledge on this subject. “Global dimming” is not well known and somewhat mysterious. The figures I have seen are more like 2-3%/decade, with a probable reversal more recently, rather than the 22% you quote. this might help – William]

  3. 3
    Louis says:

    While I am a scientist, I am not a climatologist so I thought I’d ask what the mainstream opinion is of the “Global Dimming” phenomenon. It was the subject of last night’s Horizon on BBC 2, and while that isn’t my normal source for matters scientific, it was an issue I’d forgotten about and that interested me. Are there any suitable reviews that might allow me to bring myself up to speed a bit more (yes I can search for them on SciFinder etc, but with little/no knowledge of the field, it can be hard to see the wood for the trees, no pun intended)?

    I am well aware of the cooling effect of atmospheric particulates etc (if I remember correctly isn’t it properly called albedo?) due to their more effective reflection/scattering of incident radiation. I am also aware of how this may well mean that climatological models may well be predicting lower global warming change than in actually occuring, i.e. the warming problem is more serious than it appears.

    Thanks in advance.

  4. 4
    Tony Weddle says:


    The programme was talking of 22% in five decades, not per decade. There have been articles as far back as the 70s concerning global dimming but it’s only very recently, apparently, that all of the probable causes (e.g. the microscopic particles causing smaller water droplets in clouds, enhancing the mirror effect, as well as contrails) have been understood. It’s an horrendous scenario but I’d like to see more research done, before falling on my sword.

    [Response: …and 2-3%/decade, with a recent reversal, isn’t 22%. The Liepert paper I linked to (you did read it didn’t you?) says 4% over 3 decades (*not* per decade): 1961-90. Stanhill and Cohen quote 3% between 1958 and 1992. So the 22% figure seems too large. You speak of articles from the 70’s on global dimming, but don’t say which ones you mean. Its helpful to be specific – William]

  5. 5

    Interesting — I just (last night) emailed, offering to become involved here, and mentioned the conclusion of the Loutre and Berger paper, that orbital forcing parameters will next be conducive to widespread polar ice accumulation in about 60,000 years.

    For many of us, these geological time-scale climate changes do not seem very significant. It is my feeling that there is a valuable context to be gained by keeping these time scales in mind.

    Back in 1990 I had a private correspondence with Stephen Schneider on this subject. I asked if it was plausibly justifiable to state that Earth, for at least the last 100 million years, has never been cooler than it was 20,000 years ago. His response was unqualified: “The Earth has not been demonstrably colder than 20K BP except perhaps for the Permian.”

    So for this extended period in the evolution of life on this planet, we are only very recently plunging, arguably at an accelerating rate, into previously not experienced degrees of cooling and also probably into new extremes of rapid climate variability. The ecosystems of our planet have surely been under unprecedented stress by these processes. In fact, arguably, the emergence of sentient hominids may largely be a result of the stresses of climate fluctuations following the last interglacial which ended about 114,000 years ago. (*see footnotes)

    I am old enough (Ph.D. 1978 in Atmospheric Science, Colorado State U.), to remember the discussions going on about climate cooling at the time. The backdrop of the discussions was the seeming inevitibility that “sooner or later” our planet would present us with another potential 8 or 10 degree cooling. Our current interglacial had already extended beyond the length of most others during the past 400,000 years. So, presuming humanity survives the next 60,000 years, what are we to make of this threat? How much anthropogenic warming would be needed to avert it?

    Back in 1990 Stephen Schneider’s response to this was: “I am unconcerned about 10,000 year cooling trends (which we’d likely avert with carefully selected CFC-like greenhouse gases in 1000 years, I suspect.)” My reaction to that, then and now, is: So we are potentially faced with a time when we would hope to *deliberately* induce greenhouse warming? Perhaps, then, the largely uncontrolled experiment we are currently conducting with our planet’s climate system, will prove to be a very useful exercise.

    — Peter J. Wetzel, Research Meteorologist, NASA Goddard Space Flight Center, specializing in parameterization of land-atmosphere interactions for Global Climate, Regional Mesoscale, and Local Cloud-Resolving numerical prediction models.

    (* footnote 1: This perspective makes one wonder — having emerged from this crucible of rapid (sometimes catastrophic?) climate fluctuations, should we now be fearful of them?)

    (* footnote 2: Climate Science is not black-and-white, not Right-or-wrong. Nor are its critics. One of my concerns about this web site is that it seems to occasionally lapse into rebuttals of prominent non-scientists’ statements (such as Crichton’s book) with an attitude of “everything they say is wrong”, or with an intent only to rebut, and not to find any kernel of value or truth. As much as Crichton’s book presents wildly biased perspectives on Climate and environmental science, I have to thank him for two things — first for simply raising awareness, and second, for arguing the often missed point that mankind has not inherited a stable, “preservable” environment. It was wildly changing when we arrived, and wild changes will always be the true nature of “wilderness”. In my humble opinion, this is a valuable perspective which the view of geological and evolutionary time scale climate changes can provide for us.)

    [Response: it would be odd to worry about cooling in 10,000 years time, when we have warming over the coming century to worry about first. As for the “not stable environment” bit, I think thats wrong: the holocene (last 10 kyr) *has* been fairly stable, and the rise of civilisation is sometimes attributed to that – William]

  6. 6
    John Finn says:

    The programme was talking of 22% in five decades, not per decade

    I think the 22% was the reduction measured in Israel. Different locations (in the NH) were reported to have recorded different reductions ranging from 10% to 30%. But it was implied in the programme that the Southern Hemisphere, quite reasonably, was less.

    Perhaps averaging it out over the globe explains the discrepancies between your figures.

  7. 7
    Thor Olson says:

    Wow – great article and comments.

    Am I that far off to say that the average reader who agrees with George Will is likely use their own experience of local weather as a guide to Global Warming?

    There has been a pattern for awhile where record high temperatures are recorded in Alaska on the same day that record cold is recorded farther to the more populous South and East. To many people this is simply the ebb and flow of the weather and discrediting of any notions of warming. To me it is evidence of warm air displacing cold air in the polar regions. Between us is a curious difference that suggests our approach is more of a determinent than the information itself.

  8. 8
    Steve Bloom says:

    Regarding Peter Wetzel’s footnote 2 (in #5), certainly one can say that frantic propaganda like Crichton’s is a sign that the awareness of human-caused climate disruption is permeating into parts of society that don’t like its implications. Crichton is just the most prominent of a number of libertarian SF writers who dislike the current climate science consensus because it fundamentally conflicts with their world view. I won’t try for a complete definition of this world view (read Ayn Rand for that), but in this context it results in desperate objections to the concept of an environment that might bite back when over-stressed by the net effects of human personal choices (or at least the current ones being made by these folks). Another reason they’re offended by the consensus is because they view themselves as part of a scientific intelligentsia.

    But even if climate scientists should see Crichton’s book as a sign of progress or even as a back-handed compliment, I don’t see how that should change the approach taken by this site. Peter pointed to nothing in the Crichton article that was not accurate. Given the vast propaganda machine seeking to refute the implications of human-caused climate disruption, it’s essential to have a site that can provide up-to-the-minute science-based responses to the distortions that the machine constantly places in the popular media. In an ideal world, reporters and political leaders would read the scientific journals themselves, talk to climate scientists and draw the proper conclusions, but considerable experience with both has shown that not to be the case. Something more is needed, and this site helps fill that need.

    Really, words fail me when I try to describe how valuable this site has already become despite its very brief existence. Keep up the good work!

  9. 9

    Regarding Wetzel’s comments about avoiding a glaciation, I think it’s pretty much settled that we have the technical capacity to do that. We also have the technical capacity to avoid rapid global warming. Perhaps the optimum strategy would be to tune the planet for a slight cooling from the present state, to reduce sea level slightly and thereby preserve coastal heritage and protect coastal and island populations. It’s certainly something that in a better ordered civilization we could certainly consider, and if desired, implement. Nothing prevents our doing so from a technological perspective.

    Why does this suggestion sound vaguely ludicrous?

    The problem is, all too evidently, that the world community does not have mechanisms for acting coherently and rationally on these matters. So instead of fine tuning the system, we seem intent on bashing at it harder and harder until the parts break.

    Also, I don’t see being forged in a crucible as being an especially good argument for going back into one.

    All that said, I appreciate Wetzel’s comments. It’s very refreshing to see well-informed skepticism amid all the ghastly noise.

    I agree with him that this site as a whole shouldn’t be perceived as having a policy position, not should it present some sort of false impression of unanimity on those matters that are still in serious dispute.

  10. 10
    dave says:

    Having read Imbrie & Imbrie 1979 (cited by you), it seemed obvious that whether a new Ice Age was coming soon was a research topic going forward. At the time, it seemed quite reasonable to think that the present interglacial might be similar to the Eemian in terms of duration and so therefore could end relatively soon.

    Later research I saw, especially Berger and Loutre 2000 (cited by you), indicated (quote)

    The small amplitude of future insolation variations is exceptional. One of the few past analogues occurred at about 400,000 years before the present, overlapping part of MIS-11. Then and now, very low eccentricity values coincided with the minima of the 400,000-year eccentricity cycle. Eccentricity will reach almost zero within the next 25,000 years, damping variations of the precession considerably.

    So, it was interesting to see that the latest and deepest ice core from Antarctica, Eight Glacial Cycles from an Antarctic Ice core seemed to demonstrate that Berger & Loutres were right and furthermore that we could probably expect another 15,000 years of interglacial climate even without anthropogenic forcing.

    So, this research question, established mainly in the 1970’s, is being answered.

    It’s an interesting rhetorical trick that Crichton, Will, are using. They are pointing out a false “false alarm” to buttress their “arguments”, such as they are.

    Nice post.

  11. 11
    Dano says:

    Again, I truly appreciate this site.

    Taking issue Michael Tobis’ last para:

    I agree with him that this site as a whole shouldn’t be perceived as having a policy position, not should it present some sort of false impression of unanimity on those matters that are still in serious dispute.

    is, perhaps not surprisingly, Pielke – he raises an interesting point. I don’t always agree with him, and I disagree with his basic stand, but he seems to disagree with the trajectory this site is taking already:

    Whether intended or not, the site has clearly aligned itself squarely with one political position on climate change. And by trumpeting certainty and consensus, and attacking claims to the contrary, it has fallen squarely into the uncertainty trap.

    which directly disagrees with #9 (perhaps on purpose?).

    As the ‘global cooling’ is used by ideologues with a policial axe to grind, I wonder what the thought behind posting this article could have been…



    [Response: I realise you are only quoting, but this bears repeating – We are not taking a political position. That some people have taken a poltical stand that involves ignoring well-understood science is not our fault. Correcting their errors does not ipso facto imply contradicting their politics. – gavin]

  12. 12
    Jim Norton says:

    In his bibliography (page 599) Crichton writes that Lowell Ponte’s The Cooling is “The most highly praised of the books from the 1970s that warned of an impending ice age.” Isn’t it just about the only book? Does anyone know of others?

    [Response: Nigel Calder has a book-of-a-tv-series, “The weather machine (and the threat of ice)” – William]

  13. 13
    dave says:

    I don’t think the scientists who are posting informative articles on this site are taking a political stand. They are just pointing out obvious falsehoods, distortions made about the current scientific results. This does not obviate in any way the fact that there are important uncertainties about many things.

    Things do get fuzzy. A “consensus” about many issues does not exist.

    But, as far as I can see, the “attacks” by vested interests are not even able to make legitimate points (e.g. uncertainty about the effects of clouds or aerosols in climate models). What is the reason for this? Well, these people have no interest in the science, they are only interested in their political agenda. Period.

    Leave it to people who comment, like me, to point out on occasion the political agendas. Still, I’d rather stay with the science and I think the people who post new articles here are doing the same thing.

    Importantly, what tends to happen is that a new provocation by some dimwit leads to a new informative article about the state of the science in that area.

  14. 14
    Ken says:

    Regarding “global dimming”, here are links to two related news stories:

    Why the Sun seems to be ‘dimming’

    Dim Sun

  15. 15

    To William, who responded to my #5: Perhaps it would be odd to not worry, and be accused of myopia. On your other point, yes, the Holocene had been a period of remarkably stable climate. I distinguish between the harsh climate regime in which homo sapiens would have been forced to acquire the skills of intellect and compassion for adaptation (~50,000 to ~20,000 years ago), and the benign climate regime which allowed these skills to flower into advanced civilization.

    To Steve Bloom who commented in #8 that nothing I said refuted the RealClimate posts about Crichton. I fully subscribe to these posts. They reflect my views. But the posts do criticize Crichton for making deliberate omissions, or for selective “cherry picking”. I gently return the criticism by considering a point which Crichton raised, which was ignored here.

    To Michael Tobis’ #9: I have an irrational knee-jerk reaction against deliberate human intervention on climate. Perhaps we can accomplish it, but what side-effects might we be oblivious of? I arrived on the meterological scene at a time when cloud seeding was being touted as a panacea, able to suppress everything from hail to hurricanes. I witnessed that optimism quickly shrivel in the face of experimental and theoretical advances. As a result, I’m vigilantly skeptical of the unexpected consequences of deliberately tampering with the climate system.

    You rightly respond to my weakest point: Having emerged from a chaotic and harsh environment, mankind surely sees no need to descend back into such a quagmire, given the hope that s/he can (even partially) control climate outcomes. But I argue simply that we have no need for apocalyptic pessimism about our current uncontrolled climate experiment. As a species, we have demonstrated that we possess the tools to cope.

    To Dano, #11: Roger Pielke, Jr.’s remarks actually reflected my initial reaction to this site. But on further reading (I first encountered this site only yesterday), I now perceive a serious intent to remain objective regardless of the consequences. [Roger, Jr., I suspect you are reading this — perhaps you have heard my name, as I have been a long-time acquaintance of your Dad, and fellow land-atmosphere interaction modeller. (Roger Pielke Sr. is a significant student of the influence of land-use change on observed climate change, among many other notable accomplishments)].

    My hopes for this site are high. Clever wordsmiths and litigators thrive on setting traps with rhetorical bait which they perceive to be luring the “unsuspecting” scientist into revealing “weakness” in their position. I firmly believe that the inherent common sense of the common man sees through these ploys. They understand that the litigious wordsmiths have opted for political advantage at the risk of compromising integrity of logic and reason. But the dedicated scientist will choose to take this bait with eyes wide open, in the interest of preserving the scientific integrity of their hard-earned, reproducible results.

  16. 16
    Eli Rabett says:

    The problem with invoking current injections of greenhouse gases into the atmosphere as protection against an ice age starting in 60K years, is that by then the greenhouse gases we inject today will be gone. They will be mixed back into the huge reservoir of the deep ocean, or even absorbed into the lithosphere at the deep ocean rifts.

    To be perfectly logical then we should only burn fossil fuels when we need them in about 10-100 K years.

    It is interesting that Schneider suggested adding CFCs to the atmosphere when needed to prevent an ice age. Perfluorinated compounds are much better and much more stable. A perfect illustration of the laws of unintended consequences was the introduction of perfluorinated solvents for industrial cleaning to replace CFCs. These compounds have huge greenhouse potentials and very, very long atmospheric lifetimes. They were, therefore, taken off the market a few years later and themselves replaced with compounds that had much shorter atmospheric lifetimes.

    On a lighter note, when everyone was worrying about the year 2K problem, someone wag noted that worrying about the coming ice age was the year 10K problem.

  17. 17
    Sonya says:

    Good take on the global cooling myth……Thank you for taking the time to post it.

    Here is a link to probably the most comprehensive list of global dimming research papers on the Internet……at least the best list I could find; for anyone that would be interested further in global dimming.

    Research Programs……Global Dimming Bibliography

    and Radiative Forcing of Climate Change: Expanding the Concept and Addressing Uncertainties (2005)
    Board on Atmospheric Sciences and Climate (BASC)


    I had wrote a major novella but I scrubbed it and above is what I decide to post…

    [Thanks for your comment, the GD bibliography looks good. I’m afraid I edited your text down a bit further, bunnies are a bit out of our area – William]

  18. 18
    Ferdinand Engelbeen says:

    About global dimming,

    As you may know, we have some satellites flowing around out of the atmosphere, which measure short waves (SW reflection) and heat (LW emission) from below.

    For the 20N-20S tropics part of the globe, the measurements (see: , confirmed for the 30N-30S (sub)tropics in ) are as follows:

    SW reflection: 1985-1991 no change in light reflection.
    1992 sharp increase of 9 W/m2, due to the eruption of the Pinatubo. Reduced to -2 W/m2 in 1994.
    1994-2001 constantly around -2 W/m2.

    LW emission: slowly increasing since 1985 to +2 W/m2 in 2001, with a trough in 1992 (Pinatubo) and a peak in 1998 (El Niño).

    For the 30N-30S area, the trend is -0.8 W/m2/decade for SW reflection and +3.7 W/m2/decade in the last decade.
    In the same period, there was a loss of cloud cover, both in the tropics and sub tropics (and even up to 60N-60S).

    Thus that more sunlight is reflected due to (sulphate) aerosols, as the theory behind global dimming says, is proven false.

    If there is global dimming at the surface, the only explanation possible is that more sunlight is retained in the atmosphere. Which is (only) possible with (dark brown and black) soot aerosols. Although even that is questionable, as the surface temperature in the (sub)tropics increased with near 0.1 K/decade.

    Anyway, if soot aerosols are to blame, then a reduction of them would have a cooling effect, not a warming effect…

    See also the trends of earthshine, which parralel the global dimming trends (but should be opposite to them) at:

  19. 19
    David Ball says:

    The problem is, all too evidently, that the world community does not have mechanisms for acting coherently and rationally on these matters. So instead of fine tuning the system, we seem intent on bashing at it harder and harder until the parts break.

    I have to agree with Peter Wetzel on this. You cannot tune a system you do not understand. We find ourselves in the current situation largely because of our own ignorance. I don’t believe it is a good idea to try and correct the problem by resorting to yet more ignorance. We are not talking about fine-tuning the climate system, but of altering the weather and that is a dicey proposition at best.

  20. 20
    Aaron says:

    We are not talking about fine-tuning the climate system, but of altering the weather and that is a dicey proposition at best.

    Eh? By “altering the weather,” do you mean trying to control global climate change, or something else? Explain, please.

  21. 21

    While it’s definitively *NOT* true that you can’t tune a system you don’t fully understand (as evidenced countless times daily in hospitals and clinics), I appreciate the resistance to deliberately fiddling with climate. On the other hand, that horse is already out of the barn and its too late to be closing the doors.

    Human activity is already exerting a significant influence on climate, and any effort to control that influence must ultimately have some sort of implicit or explicit goal. The only way to stop tuning the climate in the foreseeable future is to have the planet’s population get much smaller. Some would argue that humans have been substantially influencing the global environment for millenia. (see ) but there’s emerging agreement that it has been the case for at least a couple of centuries ( )

    The question is whether we should and can exert any control over this human influence. Even the modest Kyoto accord is in a sense climate tuning.

    The only clear line is between having a climate policy and having none. We will never return to the geophysical history the world would have had if humanity had not emerged. The only question is whether on one hand we continue to do climate modification blindly or on the other whether we plan our influence using the best available information.

  22. 22
    David Ball says:

    While it’s definitively *NOT* true that you can’t tune a system you don’t fully understand…

    You and I have gone in circles on this topic before. It is true that you can tune a system when you don’t have *complete* understanding of how that system works. The problem is that we don’t have anywhere near complete understanding and we must have at least some before we start tinkering. We can’t even say with any certainty what the regional impacts of increasing GHG levels are going to be 30 years from now. Altering the climate is very easy to do. Doing so with any kind of control is a far different story.

    What you are suggesting is that we take the climate system from some state A and through appropriate tuning move it to state B at some point in the future. In order to do this, we need to be able to manage the regional and local outputs from the system along the way to ensure that negative outputs are minimized and positive ones are maximized. That’s the only feasible way to get policy makers and the public on-side. If we can’t, at least with any certainty, evaluate what the regional and local impacts of increased GHG emissions are going to be, how can we possibly suggest that we know enough to further tinker with the system? Colour me highly skeptical on this issue, I’m afraid.

  23. 23
    Jason Merrell says:

    Jerry Pournelle weighs in, and Mr. Schmidt replies:

  24. 24
    George Roman says:

    RE: Global dimming. If this really is global in extent, and if it really is a 22% reduction, wouldn’t we expect a major decrease in net primary productivity (NPP)due to lower solar radiation? Yet a recent global satellite analysis indicated that NPP from 1982-1999 increased by 6%, due in part to CO2 fertilization and climate change, with large increases in the Amazon rainforest (Nemani et al., 2003, Also, there is the discrepancy in measured reflected SW radiation described in post # 18.

    [Response: the 22% figure is for one area, not globally. The global figure is more like 5%. A post on GD is in preparation, so watch-this-space – William]

    Re: Scientific objectivity and climate politics (posts #11 & #21).

    Whether you like it or not, and no matter how hard you try to remain scientifically objective, many readers will paint you with a political brush. Many of your posts try to debunk polemics disguised as scientific disputes. In particular, you often react to the common strategy of using â??scientific uncertaintyâ?? to sow doubt and to get people to believe that due to uncertainty, scientists actually know very little about the topic. When responding to these arguments you often must react by downplaying uncertainties, which can easily be interpreted by some as a political bias. I think this is a tricky communication problem that partly has to do with the common perception of ‘science’ as something that always provides solid facts and is characterized by little uncertainty (probably a product of memorizing scientific facts in high school texts). Getting people to understand the context of the slow march of the scientific process, getting them to understand scientific uncertainty, and getting them to understand exactly what is known and not known are all difficult things to accomplish. In general this site is doing a good job with this. However, as scientists communicating to the public, there is always the temptation of, as Pielke points out, â??trumpeting certainty and consensusâ??, while refraining from clearly communicating what is not known. If people then run into legitimate criticism of uncertainty and climate policy by well respected skeptics (e.g.: Lindzen), then there is the danger that they will label your site as political and not scientific, and you could lose credibility in the eyes of some people. The best way around this could be to make some posts on legitimate skepticism, based on analyses by Lindzen and others, so that people can come to a better understanding of exactly what is known and what is not known in climate science. This could then lead to a wider debate about how best to respond to climate change risks in a complex world with an uncertain future. Maybe an additional site dealing specifically with climate policy should also be set up, perhaps by economists and policy-oriented people studying the problem (e.g.: Nordhaus, Pielke, etc)?

    [Response: thanks for this thoughtful comment & ideas. A post looking at the more legitimate skepticism is a nice idea. Pielke already has a science policy site and his most recent post is about us (offering us some advice, in fact). There is scope for cooperation – William]

  25. 25
    Peter Hearnden says:

    I can see how our actions over this past century and the next may well causes a serious radical climate change. I can see how our actions over past centuries, and maybe millenia, might well have changed the climate. But I can’t see how if we reduce our effect on the climate (as any strategy to mitigate climate change would) it is another form of climate control. It would be reducing our effect, our control, not adding another – surely? 4+5 is 9 but subtracting 5 isn’t another addition?

  26. 26
    JN says:

    I’m not a physicist but I would ask this question; can a constantly irradiated object spontaneously and permanently lower its temperature?

    Suppose for example I place a toy robot in front of a heat lamp, and the toy raises a reflecting shield. Given enough time won’t conduction raise the temperature to what it would be without the shield?

    Over to you scientists.

    [Response: if the shield were a perfect mirror, then that would decrease its temperature – William]

  27. 27
    Pat Neuman says:

    “This episode shows the scientific press in a very
    good light; and a clear contrast to the lack of any
    such process in the popular press, then and now.”
    (‘The global cooling myth’ by william, 14 Jan. 2005)

    In comment #1, I asked:

    “Why has there been a lack of ‘process’ in the popular press,
    then and now? … especially in the U.S.” ???

    I’m sure some readers do not agree with my answer. Are there any readers who
    intend to post later with their thoughts on that question? Is it correct to assume
    that some readers will not reply to this out of fear that their response could
    threaten their personal awards, status or livelihood?

    The answer that I gave in #1:
    … I think U.S. government agency administrators,
    directors and managers are reluctant to make waves.

    [Response: In the post, I was contrasting scientific peer review with the processes of the popular press. The latter doesn’t appear to have anything resembling peer review, so wacky stuff is more likely to get published. Also, their audiences are less likely to notice contradications and omissions – William]

  28. 28
    Pat Neuman says:

    I think the distortion of science is greater in global climate change articles because there is no government agency taking responsiblity for providing essential information and education for the media and public, in the U.S. The media and weather-climate TV broadcasters have no authority to go to for advise. It’s therefore not surprising that their stuff is more “wacky” than other sciences that have focal points in government to help in sorting fact from fiction. The lack of a responsible government agency on global climate change explains the reasons why contrasts between scientific peer review and the processes of the popular press are greatest with the climate change issues. is supposed to be focused toward climate science, otherwise I think it would have been defined as, right?

  29. 29
    pat says:

    This article, like the comments about Michael Crichton’s book seems to be poorly aimed. What was the point of Will’s argument? What was the arena in which it was argued? The same questions may be asked about the Crichton book which makes many of the same arguments. In both cases this site produces a response that avoids the major thrust of the criticism and focuses on irrelevancies.

    The current arena in which Will and Crichton argue is not the arena of peer reviewed journals nor even of blogs by experts and would-be experts. They speak to the common level of discourse that is expressed in the mass media and by the proverbial man on the street. In this arena it may be said with some certainty that almost all weather news irrespective of type or direction is accompanied by an explanation that invokes global warming. The man-on-the-street doesn’t generally know that there have been warming and cooling trends that have no connection to CO2 levels or man’s influence. Both Will and Crichton address that kind of audience. They seek to redress the terrific imbalance in public perceptions.

    [Response: I think you are too kind too Will/Crichton. On the specific issue of this post, they are seeking to perpetuate a myth, not remove one. Ditto on a number of other issues as raised in the C posts here. Quite likely, they have been taken in by the myth themselves (which in C’s case would bely his claims to have spent years on research) – William]

    Let me make a few points of this kind that do not rely on my expertise in climate science but are very relevant. First the dispute over global warming has a strong religious element. Listen to Rush Limbaugh. He essentially argues that God made the world and man can’t change it no matter what he does. Similarly many environmental activists believe that man’s influence is a form of sin and nature(Gaea)will soon strike back. I never argue with anyone over global warming anymore than I would argue about the divinity of Christ. Global warming is very appealing to those who formerly were attracted to millenial and apocalyptic prophesies. I don’t argue with them either.

    Global warming has also been highly politicized. Democratic legislators traditionally investigate some abuse or scandal so as to advance their careers. Truman investigated war time profiteering, Kefauver investigated crime, Kennedy investigated labor, Church investigated the CIA, and Mondale investigated non-profit fund raising. In all this discourse about the validity of Hansen’s research and what he actually predicted, no mention is made of the reason for his testimony. He was granted a platform for his ideas in futherance of Al Gore’s run at the Presidency. Surely George Will should be allowed to speak on issues that bear on Presidential politics. His expertise in that area is at least as great as this site’s authors is in the area of climate science. This site likes to ignore this context and focus only on the technicalities of Hansen’s testimony. Crichton and Will in effect point out that global warming advocates can have personal career and power motives.

    [Response: we’re focussing on the science. We’re scientists, its what we do. Will and Crichton get their science wrong – William]

    Connolley charges that environmental sceptics like Will, Crichton or Limbaugh distort the truth about the opinions of climate scientists who wrote about cooling in the seventies. If you read the original documents on his site and read his commentary you will not find that there has been very much distortion. There is plenty of simplification and some over emphasis but there is no example of deliberate deception. There were climate scientists who speculated about global cooling in the seventies and there were journalists who wrote articles about the prospect of coming ice ages. Finally there were policy advocates for immediate dramatic governmental action. Connolley points out that the legitimate scientists made very guarded statements, as indeed they did. The global warming sceptics often quoted the less responsible and more sensationalistic journalists. He tries to make the point that real scientists never really predicted an ice age. That may be true but it’s hardly the point.

    [Response: no, its exactly the point. W and C are trying to say that there was a consensus around cooling/ice age, in the way there is now a consensus around GW. Thats not true. Reading the literature makes it perfectly clear – William]

    Will and Crichton’s point is that much of the media hysteria around global warming was seen around global cooling not so long ago. That point is not refuted by Collolley, but for writers like Will and Crichton it is the central point they want to reveal to their readership. It is context. It is political and social context not climate science context.

    Crichton makes a specific recommendation for double blind environmental research. This sites doesn’t address that idea at all but chooses to deal with the the examples he happened to pick for historical temperature charts. The point isn’t any particular site. The point is that most people are surprised that there are so many sites for which there has been no warming or there has been indeed cooling. His novel and Will’s article operate in an area of public discourse where everyone “knows” that global warming is real, serious and potentially catastrophic. Hardly anyone knows that the evidence is complex and controversial.

    [Response: the evidence is complex (if you look at the complex bits) but not controversial – William]

    Lomborg in his book cites a number of cases in which environmental activists have misstated or exaggerated the truth in much the way Connolley attempts to on his site. In many cases the examples of environmentalist mistatements cited by Lomborg are truly shocking. There are some outright lies and many deceptions. In contrast Connolley has found very little on the sceptics. The sceptics have not been perfect witnesses but their biases are an order of magnitude less egregious than the wild statements that come from the environmental left.

    [Response: I have attempted to correct the myth, but quoting from the actual papers, so I don’t understand your accusation that I have misstated the truth. Attempting to assert that most of the wild statements come from the “left” doesn’t seem plausible either – William]

    In point of fact I don’t agree with Crichton , Will, or Limbaugh. I think the balance of evidence currently shows that there has been some anthopogenic global warming and that it will continue and grow. I think however that the degree of warming has been and will continue to be relatively small and its economic effects will also remain small. Of course I could be wrong and I am likely to revise my opinion based on new evidence. My opinion is not based on any formal expertise but nevertheless I think it is valuable because I have no interests at stake. I get no income from relevant industries, I am agnostic on the faith dimensions, I have not applied for any research grants, and I am not running for office. In these kind of disputes freedom from interests trumps expertise.

    [Response: I’m not sure whether your “relatively small” means that you think the warming is less than generally agreed, or that you think that the 0.6 +/- 0.2 is right, but small. I recently found that George Bush agrees with the IPCC that there has been a warming of about 0.6 degrees over the last century and that there has been sharply rising temperatures from the 1970s to today – William]

  30. 30
    David Fielding says:

    I would welcome William’s views on the role played by sun-spot activity in GW. I read somewhere that we are in a phase of increased activity and I wonder what % such activity may be contributing to GW?

    [Response: This issue is addressed in our post “Senator Inhofe on Climate Change” (see discussion of ‘(1) The Paleoclimate Record’). Numerous climate modeling experiments which have included the role of natural (both solar and volcanic) radiative forcing have concluded that natural forcing cannot explain 20th century warming. -mike]

  31. 31
    Ajax Bucky says:

    “Similarly many environmental activists believe that man’s influence is a form of sin and nature(Gaea)will soon strike back…”
    You can phrase the position of a fictitious group any way you want of course, without rebuttal, because they don’t really exist, though there are people who fit the description – especially if by “many” you mean more than three – but the more accurate reality is most of the human beings you would lump under the rubric “environmentalist” would more accurately be described as believing that short-sighted and greedy human attempts at total control and domination and complete disregard for the healthof the environment have gotten us out of balance with what was an interlocking web of balanced and dynamic systems, and would appear to have unbalanced many of those systems as well, including the still poorly understood cycles of climate; or weather, as we laymen call it.
    Seeing that whole system as a living thing, or Gaia, is an interesting concept, but it isn’t central to most of us who are concerned about the health of the world our children inherit.
    It is central however to the superstitious and fearful who need to demonize any opposition to their nonsensical beliefs, including the unadorned and irrefutable truth; in this case recasting the responsible and mature concern for the health of the physical world that’s the real “belief” motivating most “environmentalists”, as “pagan” “nature worship”.
    Horse feathers on both sides, but the concern’s still valid, and it takes more courage to live with than superstitious claptrap, or as-yet still-comfortable denial.

  32. 32
    George Roman says:

    Pat (post #29) claims there is a ‘terrific imbalance in public perceptions’ and that ‘everyone knows that global warming is real, serious and potentially catastrophic’. What evidence is there in favour of this assertion? The media coverage of the topic that I’ve seen (in the US and Canada) does seem very stilted and unbalanced, but in the opposite direction, especially recently. There seems to be an overemphasis on the uncertainty of climate modeling, attacks on climate science, and op-ed pieces that distort science and use sensationalist rhetoric and wild conspiracy theories. For example, an editorial I read today in the ‘Calgary Herald’ suggests that the Canadian ‘pollution police’ want people to ‘stop breathing deeply’ or to ‘stop burning things to keep warm’!! This is not what I would call unbiased coverage of the science (or the policy for that matter), and this is definitely not biased in the direction that Pat claims.

    But let’s not rely on individual anecdotes. One recent study empirically examined the effects of US media coverage on environmental concern and environmental knowledge (Besley & Shanahan, 2004; Society and Natural Resources 17 (10): 861). A major conclusion was that: “…a strong relationship between stilted media coverage and heightened environmental concern is generally not consistently borne out by the data.” They also state that “…even the contention that media content is overwhelmingly proenvironmental seems a significant stretch…”.

    The fact is, there’s plenty of bias in the media on this issue, and very little evidence to support the contention that the bias is slanted towards environmentalism. There is no doubt that some environmentalists make exaggerated claims on global warming, but when was the last time these were shown in a major news outlet? There is also no doubt that there are powerful political and economic interests funding disinformation campaigns with their own exaggerations, and it seems to me that these have lately been making it into the news more than the claims of environmentalists. In my opinion, neither side should rely on propaganda and rhetoric. Disinformation should be fought with the truth, and neutral, objective, balanced analysis. Hopefully, will emerge to partially fulfill this need.

  33. 33
    John Finn says:


    I notice a response by you which says

    At the last glacial maximum (20,000 yrs ago), forcings by ice sheets, vegetation, greenhouse gases and dust loading are estimated to be around -7W/m2, and that sustained a climate 5 to 6 degrees cooler than present. This is consistent with the model estimates, and provides a severe test for those who would argue that the sensitivity is much less (say <1 deg C). If sensitivity is that low, then the forcing at the LGM needs to have been more like -20 to -25 W/m2 – and where would that come from?

    What about Water Vapour? In a much colder climate, evaporation would be less. Wouldn’t it only need a change of a few percent in WV to alter the WV forcing by 4 or 5 W/m2.

    [Response: Water vapour can be considered a fast feedback. It was almost certainly less at the LGM because of the negative forcing. But that is taken into account in this example. In fact the great thing about the LGM is that all fast feedbacks must be taken into account – even the ones we don’t know about. Thus if this tells us that sensitivity is near 3 degrees, and that is close to the model estimates, we can have some confidence that we have captured the main feedbacks. – gavin]

  34. 34

    Post#32 deals with public perceptions of global warming.
    An excerpt from a post today at the globalwarming yahoogroup
    that discusses a poll of 753 Americans on Climate Change
    indicates that:

    “most Americans have heard of Global Climate Change
    but believe that the effects will be slow in coming”…

    That’s has been my experience over the last five years
    with my perceptions of the viewpoints of my
    coworkers, supervisors, directors and administrators
    with the agency thart I’ve been employed with as a
    hydrologist for 25 years.

    At: globalwarming yahoo group
    Tue Jan 18, 2005 7:37 pm
    Subject: American Poll on Climate Change

    I found a 2004 poll of 753 Americans on
    Climate Change. To find it, use and search for
    . . . poll PIPA “climate change” . . .

    The gist is that most Americans have heard of
    Global Climate Change but believe that the
    effects will be slow in coming so we should
    take slow, cheap steps for now. Americans
    are heavily divided on everything to do with
    the topic, and their answers reflect a lack
    of understanding of GCC politics.

  35. 35
    pat says:

    I thank the authors of this site for their civility and the other commentators for their temperate remarks. However I think all of you have illustrated my points by your objections.

    I expect and I welcome real science being applied to this and all other similar issues. My point was that the non-scientists Will and Crichton should be listened to because they are giving testimony about the possibility of social-political issues involving bias. As The Amazing Randi as pointed out scientists are rather easy to fool by charlatans and magicians because of their relative innocence. Similarly I would submit that scientists generally underestimate the social impacts and influences involved in these kind of issues. Political commentators and novelists may have better perspective.

    Specifically Will and others have commented on the media ice age hysteria in the mid seventies. I have read everything on Connolley’s site and no matter how it mitigated, the point remains that when temeperatures went down there were popular press accounts that predicted ice ages. Today we have had popular press accounts predicting run away warming. Surely it can’t be wrong to review the record and at least wonder. As I understand the scientific consensus – there was warming in the early part of the century, cooling in the middle and warming again in the second half. The recent warming seems to correspond very well with the anthopogenic CO2 increases but the explanations for the earlier two trends are much less obvious.

    [Response: I think you’re missing the point. I’m saying, look at the science, not the popular media. Happily, the science is readily available, in the shape of the IPCC TAR. The explanations for the earlier trends have been provided: for the early warming, a mix of natural and CO2; for the cooling, naural variability and sulphates and a bit of other stuff – William]

    Your response to Will’s political article reads like a political retort. We have quite enough of that sort of thing on Fox News. Because global warming is so much a Democratic Party issue Will as a Republican treats it as another grist for his partisan political mill. You can respond to a partisan polemic in a partisan fashion but I think it wiser to rise above that level of discourse. Connolley’s site seems to be oriented around the concept of “gotcha”. I recommend responding with a balanced and impartial review of the evidence. Dare to be boring. Don’t attribute low motives to global warming sceptics. Rather try to show them the error of their ways.

    [Response: well, you start with civility and then compare us to Fox News. Thats not nice. For the record, I reject your comparison. My site is orientated around the science – William]

    Crichton argues for double blind funding. By this stance he is asserting that climate scientists may be bias. This is probably personally difficult for the scientists to accept but it is certainly consistent with good science. When I taught research design often my students couldn’t always see the necessity for such caution but I would expect all physical scientists to embrace this kind of reform. Crichton seems to be a kind of modern day Semmelweis, castigated for advocating a needed reform.

    Ajax Bucky (#31) doesn’t recognize to whom I refer when I spoke of environmental groups who see human development as a form of sin. If he will reread his own post I think he will see an example of this over heated sort of thinking. He uses the terms short-sighted, greedy, total control, domination, etc…. These are the words of a person consumed by a quasi-religious passion. I don’t think the discussion is advanced by demonizing the opposition.

    In my regular work I have always had to deal with religious passions – generally Microsoft vs UNIX. These disputes involve and consume the brightest people. Brilliant technical people often become enraged by such questions. Such disputes are aptly called “religious wars”. This sort of thing is what I meant by the observation that there was a religious dimension to the global warming controversy. I expect the appropriate scientists to resolve the facts of the matter dispassionately of course but everyone should recognize the out-size emotions that have been let loose. Remember Magdeburg and Drogeda.

    George Roman (#32) contends that I have exaggerated when I claimed that there has been a ‘terrific imbalance in public perceptions’. He cites a study that criticized Lomborg for making similar claims. Alas I refuse to spend the $23.18 required to read more than the abstract. Rather I will just ask – Why was Lomborg’s book so shocking?. Why did Crichton spend most of the plot having his characters reveal problems with popular perceptions about global warming? Why did Will bother to write about global warming at all?

    All three of them seemed to believe (as I do also)that the general public has been told a consistent tale of alarm by the media. If they were wrong in this perception and the public was well informed on all sides of this issue then no one would have noticed an obscure Scandinavian economist rehashing old news and no one would have commented on yet another sci-fi thriller from a not particularly talented writer. I suggest you consider the wisdom of the market. Will, Lomborg, and Crichton each in his own way has found fame and fortune through exploiting what is clearly to most people a contrarian position.

    As to William Connelley’s question in his fisk of my post – I don’t know what I mean by small. Presumably that’s your job. I will say however that in graduate school and for a few years after I did mathematical modeling professionally in areas that were also politically charged. After that experience I developed an appreciation for limits of models and the power of politics. When I scan the summary IPCC model predictions I am not very compelled by what I see. I note that the long term trend of the predictions about the magnitude of global warming has been to decrease over time. When I say small I mean that I expect the effect to be of little import in human economic or social terms. This view is in contrast to the other likely result that the whole issue will evaporate like predictions of the Club of Rome and Erlich. I think there is probably something to anthropogenic global warming and I think in a few years many questions will be answered.

    [Response: the claim about a trend towards lower predictions is a common skeptic claim, but its not true – William]

    To increase the credibility of this site may I suggest that all the contributors post their political party affliation, their connections with industry and environmental groups, and their source of funding. Remember, Al Gore raised global warming to run for the Presidency. Bill Clinton signed the Kyoto Treaty which he knew to be unpassable by the Senate as a political ploy. George Bush killed Kyoto as a Republican counter stroke. Global warming is one of the most powerful political issues extant. We need to know your personal politics in order to evaluate your comments.

    [Response: no you don’t. This site is for science, not politics – William]

    We also need to know of your other affiliations and funding sources. I always thought there were billions at stake over global warming but Crichton says trillions. Whatever. This is not molusc paleontology. There is big money involved and money matters – so do ideological commitments. When you understand that Gould was a life long commited Marxist you understand his essays differently.

    Like many others I would like to find a solid, reputable, and credible source of information on these most controversial questions.

    [Response: Happy you, for you have found it, and its called RealClimate and/or the IPCC TAR – William]

  36. 36
    mtneuman says:

    In post #35, pat said: … “When I scan the summary IPCC model predictions I am not very compelled by what I see. I note that the long term trend of the predictions about the magnitude of global warming has been to decrease over time….”

    Two comments – One, the 2001 model predictions thus far have turned out to be quite accurate when compared to real world climate changes. In fact, if anything, I would say that the IPCC predictions underestimated the speed at which global warming is now progressing. Granted, while the globally averaged annual temperatures for the years since the record warm year of 1998 have not exceeded the 1998 record, the global temperatures since 1998 have remained high, ranking as the second, third and fourth warmest years of the last 125 years (and quit possibly the last 2,000 + years). There is every reason to believe the record warm year of 1998 will soon be broken, given the trend of changes we have been seeing occurring throughout the planet in the last several years.

    For example, we have seen the ice and snow extent greatly decrease throughout the world, reflecting unprecedented rates of melting in modern time. The melting has been extensive on the Arctic Ocean, in Alaska, Greenland, Antarctica and in the mountainous regions of every continent. There have been major disruptions in biological ranges and the world’s ecological communities – communities which had previously remained intact for eons, but are now dispersing.

    Moreover, reports from NASA suggest the ocean levels will rise more than the IPCC had initially predicted, due to the rapid melting on land masses throughout the world.

    With all these changes now actually occurring (rather than just predicted), and occurring much sooner than anyone had ever predicted as well; the claims by Michael Crichton and others that those of us who are demanding immediate action by Government, citizens and businesses to greatly reduce greenhouse gas emissions are “environmental alarmists” are factually without merit and represent exaggerations in and of themselves.

    To have any hope of slowing the pace and holding down the upper level temperatures that global warming will bring over this century, the human population of the world will need to make large reductions of the additional billions of tons of greenhouse gases they are projected to be pumping into the atmosphere, each year.

    Two – Please substantiate your claim that the IPCC predicts the long term trend of the magnitude of global warming has been to decrease over time…. Everything I’ve seen suggest that, with the human component, we can expect global warming to continue – indefinitely.

  37. 37

    Mythos Eiszeit
    Leider schon ein paar Tage alt, aber eben erst bei uns eingetroffen, ein interessanter Artikel darber, wie es immer wieder zu Berichten ber eine kommende Eiszeit kommt. RealClimate The global cooling myth…

  38. 38
    Peter says:

    I note with interest Pat’s attempt to hoist this site on the cleft stick of “disclosure”: either the authors reveal their political beliefs and economic resources and expose themselves to attack because of affiliations that don’t guarantee objectivity to Pat’s satisfaction, or their integrity is impugned by the implication that they are hiding their biases. Fortunately, this is a science site with evidentiary standards and Pat will have to do the hard work himself of tearing down the authors by understanding and rebutting the publically available and peer-reviewed research and the authors’ presentation of it. They are under no obligation to provide grist for his political mill or opportunities for lazy innuendo.

  39. 39
    George Roman says:

    Re: #35. Pat, you noted that: “George Roman (#32) contends that I have exaggerated when I claimed that there has been a ‘terrific imbalance in public perceptions’. He cites a study that criticized Lomborg for making similar claims……Why was Lomborg’s book so shocking?. Why did Crichton spend most of the plot having his characters reveal problems with popular perceptions about global warming? Why did Will bother to write about global warming at all?”

    I think this is mostly because the media likes to run stories about juicy confrontations and political intrigue. Also, you have a much higher chance of getting the attention of the media and the public when you oversimplify complex scientific topics, exaggerate, use shrill language, etc. Unfortunately, this problem seems to apply equally to environmental NGOs as well as to Lomborg and Chrichton. The simple fact is that for most people, detailed scientific analysis is utterly boring. This is why dry scientific articles in journals tend to stay in those science journals. Essentially, people like Chrichton and Lomborg are pitching interesting stories directly to the mass media. If everybody in society completely believed and trusted some of the shrill messages of impending doom and ‘the sky is falling’, then yes, Chrichton and Lomborg would be usefully adding to public understanding of the issue. But I just don’t see good evidence that society has been manipulated by environmentalists-most people nowadays take the messages of groups like Greenpeace with a grain of salt. Yet some of the key messages of Lomborg and Chrichton, as reported in the media, are that ‘environmental scientists’ and ‘environmentalists’ are one and the same(e.g.: do not believe the IPCC reports, they are written by environmental alarmists who don’t do good science). This is a gross oversimplification. This might be an excellent way to sell books and to get attention and fame for yourself, but it’s not the way that proper science is done.

    If their messages truly helped people to understand the difference between activist environmentalists and environmental scientists, then that’s excellent. But if it makes people think that all and any environmental problems are a sham, this is a tremendous disservice to society.

    Lomborg and Chrichton simply don’t seem to understand the full complexity and nuances of the topics about which they’re writing. What they do seem to understand is how to get attention and sell books. I’m not implying that Chrichton and Lomborg have bad intentions and are dishonest. They may have some good messages, but making oversimplified one-sided statements that are ‘sexed up’ for the media and public consumption completely ruins their message and leads to public confusion and a drain on the time of scientists.

  40. 40
    Matt Lucas says:

    Here is my issue with complex modeling. I work with a service group that works on Doppler Radars. These are million dollar computer enhanced machines that are fed into other computers that do nothing but compute complex weather models. Their output is read by experienced and trained meteorologists or scientists.

    Yesterday my local weather service using the most advanced technology predicted the low for my city would be 27, my own thermometer read 18 degrees last night and there was no wind. The weather service also gave me a 50% chance of precipitation.

    How are we supposed to listen to climate scientists and weather models making predictions 10-100 years from now when we can’t get the weather tomorrow right?

    I am not a global warming denyer, nor am I a true believer, and I have usually found that the truth lies somewhere in between. Are there any web sites that provides the mathmatical model calculations for Global Warming predictions?

  41. 41
    Silent E says:

    Re: Cooling – what of Ruddiman’s suggestion that pre-industrial anthropogenic warming over the last 8000 years probably averted the re-glaciation of Canada?

    Maybe the “we’re overdue for an ice age!” scare of the 1970s wasn’t as wrong as the climate skeptics suggest.

    [Response: Ruddimans stuff is still controversial. Its an interesting idea but I don’t think many people accept it. The science of the 1970’s should be judged on its own terms though, not with what we know now. Then, they knew they didn’t know enough to make predictions; now we know enough to predict warming – William]

  42. 42
    Silent E says:

    “Ruddimans stuff is still controversial. Its an interesting idea but I don’t think many people accept it.”

    It’s certainly new. But why controversial? I’m not an expert, and the paper includes lots of hand-wavy calculations for total amounts of CO2 and CH4 released through rice-farming and deforestation-reforestation – but I find it hard to beleive that the amounts are so trivial as to be negligible for climate purposes. The scale of tropical deforestation in the last 40 years is stunning – even if it took ten times as long, early human farmers could have deforested most of temperate Eurasia in far less than 1000 years.

    Is the controversy about mechanism or magnitude?

    [Response: even with tropical deforestation, most CO2 (about a 6:1 ratio from memory) is from fossil fuel use. “controversial” is perhaps too strong: many will simply be unaware of it. “not yet fully assessed” would perhaps be fairer. Having briefly glanced at it, his main argument seems to come from overlaying the CO2 records at the same stage of different glacial cycles, and that seems quite hard to do, to me – William]

  43. 43
    Jim says:

    They were teaching Global Cooling at the time, who cares if it was not “in the scientific press”? Textbooks matter.

    From Physical Geology by Eugene Mitacek, 1971:

    “WILL THE ICE AGES RETURN? Climatologists report that the world’s weather is turning sharply cooler. Signs of this are evident. Drifting icefields have hindered access to Iceland’s ports for the first time in this century. Since 1950 the growing season in England has been shortened by two weeks. Director Reid Bryson of the Institute for Environmental Studies at the University of Wisconsin reports that, if this trend continues, it will affect the whole human populace. A long term study of climactic conditions would place the first half of the twentieth century into an exceptionally warm period. The warming trend peaked in 1945, and the temperatures have been dropping since. The drop to date is on 1.5 degrees C, far from the 10 degrees C drop necessary for a new Ice Age. If this trend is not reversed, however, the planet may be caught in an ice-forming cycle similar to that of the Pleistocene.”

    [Response: textbooks do indeed matter – thanks for this interesting quote. 1971 is curious – if you read the 1970 SCOPE report you’ll find no obvious interest in cooling; although by 1972 there was an edition of Quaternary Research on The end of the present interglacial. But the Quat Res stuff is heavily qualified. I wonder if the source you quote has any material above/below your quote that might qualify it? In fact, I’d be curious to know if you’ve read the text you’re quoting: your quote is identical to this – William]

    [Update: 2005/02/09: the reference for this work is wrong above: it should, apparently, be Charles J. Cazeau, Robert D, Hatcher, Jr.; and Francis T. Siemankowski. I have it on order from abebooks, so I’ll comment further when I’ve read it – William]

    [Update 2005/02/28: see – William]

  44. 44
    Silent E says:

    Odd – for an alleged climate textbook, I find no references anywhere. The only Eugene Mitacek in Google is an Associate Professor in epidemiology at the SUNY Stonybrook Med School.

    The only mention of a textbook by anyone with that name comes in a comment and an essay, both by the same person, from 2001 at the climate-doubting website William linked to.

    Sounds like a hoax, to me.

  45. 45

    Science Open Thread
    New Blog: Check out Squid Blog, featuring the latest on the elusive Giant Squid and other semi-mythical monsters. HT: Collision Detection. Prof. PZ Myers with a fabulous peice on Metazoan Evo-devo … OK you pervs, and the obligatory cephalopod snuff…

  46. 46
    Klaus Flemloese says:

    Dear Real Climate

    In respect of Lomborg please refer to the following link:

    This homepage is written by Kare Fog, a freelance biologist from Denmark.
    Kare Fog has identified 101 errors and 187 flaws.

  47. 47
    Jan Hollan says:

    Thanks for this wonderful site and articles, I came accros it just today. I can add something on future ice ages, as an astronomy teacher.

    To understand the causes of glacial cycles, I looked at relevant data (northern polar circle summer insolation) and used the computer code by Laskar et al 1993 to compute future insolations. As I see, it was in 2000 too, like Loutre and Berger (I don’t know that paper, as it is not online), but I remained content with making a graph with a short educational text, so that I could use it when lecturing about climate change. I just put it on my web, not knowing if there are any papers on the issue. It seemed so trivial to me.

    My results are in a file orb_forc.*, a html or pdf version. The title is No soon Ice Age, says astronomy. The conlusion that no cooling before 60 000 years can happen is evident, but quite probably whole 0.13 Ma or 0.6 Ma of a “happy postglacial” is ahead of us.


    [Response: Thanks for this. I’ll add a link from my page – William]