Disputing the ‘consensus’ on global warming

Science is in many ways the opposite of decision by consensus.

I have never liked the use of the word “consensus” as it is typically applied in the climate arena.  Scientists don’t really have a ‘consensus’ so much as they have an ‘understanding‘ of climate science.

I wrote an article on this subject in 2008, “The cold truth about climate change:  [Disinformers] continue to insist there’s no consensus on global warming. Well, there’s not. There’s well-tested science and real-world observations [that are much more worrisome].”

When James Hansen read the first draft of the piece, he wrote me back, “Very important for the public to understand this “” why has nobody articulated this already?” I don’t know.

The subject arises again because of some ill-chosen words by climatologist Mike Hulme in an article, “Climate Change: what do we know about the IPCC?”  The anti-science crowd had a blow out and started spewing millions of gallons of disinformation, such as the National Post‘s “The IPCC consensus on climate change was phoney, says IPCC insider.”

Hulme has now issued two clarifications on his website.  The bottom line:  Not every scientist involved in the IPCC process agrees with every single word in every document.  Duh.

Even Hulme’s original paper made clear that many IPCC scientists thought the IPCC lowballed likely sea level rise this century.  Double duh (see “Scientists withdraw low-ball estimate of sea level rise “” media are confused and anti-science crowd pounces“).

Hulme himself believes, the IPCC is an “entirely credible process of knowledge assessment” and “that the warming of the climate system is unequivocal and that most of the observed increase in global average temperatures since the mid 20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations.”

A good example of how the ‘consensus’ process confuses people — especially the anti-science crowd, which gloms onto any apparent disagreement among scientists as evidence against the ‘consensus’ — can be found in two DotEarth posts on “Andrew A. Lacis, the  NASA climatologist  whose 2005 critique of the United Nations climate panel was  embraced by bloggers seeking to cast doubt on human-driven climate change” (Part I and Part II).
Lacis had commented on the Fourth Assessment, “There is no scientific merit to be found in the Executive Summary.”  WattsUpWithThat got all hot cool and bothered, writing, “Remember, this guy is mainstream, not a sceptic.”  After pointing out the IPCC authors’ response, “Rejected. [Executive Summary] summarizes Ch 9, which is based on the peer reviewed literature,” WattsUp wrote, “Simply astonishing. This is a consensus?”

Then Lacis explained exactly what he meant on DotEarth:

Human-induced warming of the climate system is established fact….

My earlier criticism had been that the IPCC AR4 report was equivocating in not stating clearly and forcefully enough that human-induced warming of the climate system is established fact, and not something to be labeled as “very likely” at the 90 percent probability level.


The bottom line is that CO2 is absolutely, positively, and without question, the single most important greenhouse gas in the atmosphere. It acts very much like a control knob that determines the overall strength of the Earth’s greenhouse effect. Failure to control atmospheric CO2 is a bad way to run a business, and a surefire ticket to climatic disaster.

Doh!  He thought the IPCC ‘consensus’ was some watered down, least-common denominator piece of wishy-washiness that understates our scientific understanding, which it is.

And that brings me to my Salon piece, which I excerpt below:

The more I write about global warming, the more I realize I share some things in common with the doubters and deniers who populate the blogosphere and the conservative movement. Like them, I am dubious about the process used by the U.N. Intergovernmental Panel on Climate Change (IPCC) to write its reports. Like them, I am skeptical of the so-called consensus on climate science as reflected in the IPCC reports. Like them,

I disagree with people who say “the science is settled.” But that’s where the agreement ends.

The science isn’t settled — it’s unsettling, and getting more so every year as the scientific community learns more about the catastrophic consequences of uncontrolled greenhouse gas emissions.

The big difference I have with the doubters is they believe the IPCC reports seriously overstate the impact of human emissions on the climate, whereas the actual observed climate data clearly show the reports dramatically understate the impact.

But I do think the scientific community, the progressive community, environmentalists and media are making a serious mistake by using the word “consensus” to describe the shared understanding scientists have about the ever-worsening impacts that human-caused greenhouse gas emissions are having on this planet. When scientists and others say there is a consensus, many if not most people probably hear “consensus of opinion,” which can — and often is — dismissed out of hand. I’ve met lots of people like CNBC anchor Joe Kernen, who simply can’t believe that “as old as the planet is” that “puny, gnawing little humans” could possibly change the climate in “70 years.”

Well, Joe, it is more like 250 years, but yes, most of the damage to date was done in the last 70 years, and yes, as counterintuitive as it may seem, puny little humans are doing it, and it’s going to get much, much worse unless we act soon. Consensus of opinion is irrelevant to science because reality is often counterintuitive — just try studying quantum mechanics.

Fortunately Kernen wasn’t around when scientists were warning that puny little humans were destroying the Earth’s protective ozone layer. Otherwise we might never have banned chlorofluorocarbons in time.

Consensus of opinion is also dismissed as groupthink. In a December article ignorantly titled “The Science of Gore’s Nobel: What If Everyone Believes in Global Warmism Only Because Everyone Believes in Global Warmism?” Holman W. Jenkins Jr. of the Wall Street Journal editorial board wrote:

What if the heads being counted to certify an alleged “consensus” arrived at their positions by counting heads?It may seem strange that scientists would participate in such a phenomenon. It shouldn’t. Scientists are human; they do not wait for proof. Many devote their professional lives to seeking evidence for hypotheses, especially well-funded hypotheses, they’ve chosen to believe.

Less surprising is the readiness of many prominent journalists to embrace the role of enforcer of an orthodoxy simply because it is the orthodoxy. For them, a consensus apparently suffices as proof of itself.

How sad that the WSJ and CNBC have so little conception of what science really is, especially since scientific advances drive so much of the economy. If that’s what Jenkins thinks science is, one would assume he is equally skeptical of flossing, antibiotics and even boarding an airplane.

(Note to WSJ: One reason science works is that a lot of scientists devote their whole lives to overturning whatever is the current hypothesis — if it can be overturned. That’s how you become famous and remembered by history, like Copernicus, Galileo, Newton, Darwin and Einstein.)

In fact, science doesn’t work by consensus of opinion. Science is in many respects the exact opposite of decision by consensus. General opinion at one point might have been that the sun goes around the Earth, or that time was an absolute quantity, but scientific theory supported by observations overturned that flawed worldview.

One of the most serious results of the overuse of the term “consensus” in the public discussion of global warming is that it creates a simple strategy for doubters to confuse the public, the press and politicians: Simply come up with as long a list as you can of scientists who dispute the theory. After all, such disagreement is prima facie proof that no consensus of opinion exists.

So we end up with the absurd but pointless spectacle of the leading denier in the U.S. Senate, James Inhofe, R-Okla., who recently put out a list of more than 400 names of supposedly “prominent scientists” who supposedly “recently voiced significant objections to major aspects of the so-called ‘consensus’ on man-made global warming.”

As it turned out, the list is both padded and laughable, containing the opinions of TV weathermen, economists, a bunch of non-prominent scientists who aren’t climate experts, and, perhaps surprisingly, even a number of people who actually believe in the consensus.

But in any case, nothing could be more irrelevant to climate science than the opinion of people on the list such as Weather Channel founder John Coleman or famed inventor Ray Kurzweil (who actually does “think global warming is real”). Or, for that matter, my opinion — even though I researched a Ph.D. thesis at the Scripps Institution of Oceanography on physical oceanography in the Greenland Sea.

What matters is scientific findings — data, not opinions. The IPCC relies on the peer-reviewed scientific literature for its conclusions, which must meet the rigorous requirements of the scientific method and which are inevitably scrutinized by others seeking to disprove that work. That is why I cite and link to as much research as is possible, hundreds of studies in the case of this article. Opinions are irrelevant.

A good example of how scientific evidence drives our understanding concerns how we know that humans are the dominant cause of global warming. This is, of course, the deniers’ favorite topic. Since it is increasingly obvious that the climate is changing and the planet is warming, the remaining deniers have coalesced to defend their Alamo — that human emissions aren’t the cause of recent climate change and therefore that reducing those emissions is pointless.

Last year, longtime Nation columnist Alexander Cockburn wrote, “There is still zero empirical evidence that anthropogenic production of CO2 is making any measurable contribution to the world’s present warming trend. The greenhouse fearmongers rely entirely on unverified, crudely oversimplified computer models to finger mankind’s sinful contribution.”

In fact, the evidence is amazingly strong. Moreover, if the relatively complex climate models are oversimplified in any respect, it is by omitting amplifying feedbacks and other factors that suggest human-caused climate change will be worse than is widely realized.

The IPCC concluded last year: “Greenhouse gas forcing has very likely (>90 percent) caused most of the observed global warming over the last 50 years. This conclusion takes into account … the possibility that the response to solar forcing could be underestimated by climate models.”

Scientists have come to understand that “forcings” (natural and human-made) explain most of the changes in our climate and temperature both in recent decades and over the past millions of years. The primary human-made forcings are the heat-trapping greenhouse gases we generate, particularly carbon dioxide from burning coal, oil and natural gas. The natural forcings include fluctuations in the intensity of sunlight (which can increase or decrease warming), and major volcanoes that inject huge volumes of gases and aerosol particles into the stratosphere (which tend to block sunlight and cause cooling)….

Over and over again, scientists have demonstrated that observed changes in the climate in recent decades can only be explained by taking into account the observed combination of human and natural forcings. Natural forcings alone just don’t explain what is happening to this planet.

For instance, in April 2005, one of the nation’s top climate scientists, NASA’s James Hansen, led a team of scientists that made “precise measurements of increasing ocean heat content over the past 10 years,” which revealed that the Earth is absorbing far more heat than it is emitting to space, confirming what earlier computer models had shown about warming. Hansen called this energy imbalance the “smoking gun” of climate change, and said, “There can no longer be genuine doubt that human-made gases are the dominant cause of observed warming.”

Another 2005 study, led by the Scripps Institution of Oceanography, compared actual ocean temperature data from the surface down to hundreds of meters (in the Atlantic, Pacific and Indian oceans) with climate models and concluded:

A warming signal has penetrated into the world’s oceans over the past 40 years. The signal is complex, with a vertical structure that varies widely by ocean; it cannot be explained by natural internal climate variability or solar and volcanic forcing, but is well simulated by two anthropogenically [human-caused] forced climate models. We conclude that it is of human origin, a conclusion robust to observational sampling and model differences.

Such studies are also done for many other observations: land-based temperature rise, atmospheric temperature rise, sea level rise, arctic ice melt, inland glacier melt, Greeland and Antarctic ice sheet melt, expansion of the tropics (desertification) and changes in precipitation. Studies compare every testable prediction from climate change theory and models (and suggested by paleoclimate research) to actual observations.

How many studies? Well, the IPCC’s definitive treatment of the subject, “Understanding and Attributing Climate Change,” has 11 full pages of references, some 500 peer-reviewed studies. This is not a consensus of opinion. It is what scientific research and actual observations reveal.

And the science behind human attribution has gotten much stronger in the past 2 years (see a recent literature review by the Met Office here).

That brings us to another problem with the word “consensus.” It can mean “unanimity” or “the judgment arrived at by most of those concerned.” Many, if not most, people hear the second meaning: “consensus” as majority opinion.

The scientific consensus most people are familiar with is the IPCC’s “Summary for Policymakers” reports. But those aren’t a majority opinion. Government representatives participate in a line-by-line review and revision of these summaries. So China, Saudi Arabia and that hotbed of denialism — the Bush administration — get to veto anything they don’t like. The deniers call this “politicized science,” suggesting the process turns the IPCC summaries into some sort of unscientific exaggeration. In fact, the reverse is true. The net result is unanimous agreement on a conservative or watered-down document. You could argue that rather than majority rules, this is “minority rules.”

Last April, in an article titled “Conservative Climate,” Scientific American noted that objections by Saudi Arabia and China led the IPCC to remove a sentence stating that the impact of human greenhouse gas emissions on the Earth’s recent warming is five times greater than that of the sun. In fact, lead author Piers Forster of the University of Leeds in England said, “The difference is really a factor of 10.”

Then I discuss the evidence we had even back in 2008 that the IPCC was underestimating key climate impacts, a point I update here.

The bottom line is that recent observations and research make clear the planet almost certainly faces a greater and more imminent threat than is laid out in the IPCC reports. That’s why climate scientists are so desperate. That’s why they keep begging for immediate action. And that’s why the “consensus on global warming” is a phrase that should be forever retired from the climate debate.

The leading scientific organizations in this country and around the world, including all the major national academies of science, aren’t buying into some sort of consensus of opinion.  They have analyzed the science and observations and expressed their understanding of climate science and the likely impacts we face on our current emissions path — an understanding that has grown increasingly dire in recent years (see “An illustrated guide to the latest climate science” and “An introduction to global warming impacts: Hell and High Water“).

Of course, the status quo media doesn’t get this at all (see Boykoff on “Exaggerating Denialism: Media Representations of Outlier Views on Climate Change”; Freudenburg: “Reporters need to learn that, if they wish to discuss ‘both sides’ of the climate issue, the scientifically legitimate “other side” is that, if anything, global climate disruption is likely to be significantly worse than has been suggested in scientific consensus estimates to date”).

And here’s our favorite Michael Tobis (and Stephen Ban) graphic represenatation “” click on it for a clean image:

The time to act was a long time ago, but the longer we wait, the more the big bell curve shifts to the right and the more the “catastrophe” tail fattens.

For more on the Hulme kerfuffle, see Deep Climate.

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18 Responses to Disputing the ‘consensus’ on global warming

  1. Rick Covert says:


    I frequently contribute to a podcast on electric vehicle transportation and the two hosts deny global warming or that it is caused by man. I was content to respectfully disagree because, on balance, they are pro-EV and renewables and the information they provide on the EV world has been invaluable. That has begun to change though as they are now putting out red-herring arguments like what if global warming were a hoax but EV proponents still used it as a fear tactic to advocate the change from gasoline powered cars to ones that ran on electricity. They essentially were trying to make the argument that scientists and those arguing to reduce our carbon foot print are doing so for malevolent reasons. I don’t know how you argue with that logic, or lack there of. I don’t know what if it turns out that the electrical grid is powered by pink unicorns?

  2. Peter Mizla says:

    Thanks for the fine post.

    Over at the Huffington post a climate Denier responded to a post I made that Climate Science was the same as ‘Flying Saucers’ & ‘Bigfoot’

    my response was;

    Says who? Michelle Bachmann? Steve Doocy? How about the Club for Growth?

    Science is a very rigorous endeavor- ‘Flying Saucers and Bigfoot are not science but opinion based on no real hard data and evidence that has been reliably tested.

    You are very confused- get an education and learn about the Scientific method’ that method brought us the Atomic Bomb and a cure for polio- hardly the stuff of UFO’s and The abominable Snowman.”

  3. catman306 says:

    Here’s some more extreme weather evidence of global warming and climate change, this time in France:

  4. Dana says:

    It’s Rick from Houston! I haven’t listened to the EVCast for a long time. Back when I did, every so often they would start to discuss global warming, and would always make a number of erroneous statements. As I recall, you and I and many other listeners would subsequently correct them, and they resolved to just stop talking about the subject and stick to EVs.

    I recall thinking at the time that this was a good decision, and it’s unfortunate if they’ve changed their policy again. To say it’s outside their area of expertise and body of knowledge is a massive understatement.

    Very good Salon piece, Joe.

  5. Raul says:

    thank you for putting many links and space for others
    to put links.
    The information y’all provide is helpfull to understand
    why the weather is different from before and what
    concerns are held by others.

  6. Great Alamo metaphor Joe.

  7. Matto says:

    Joltin’ Joe hits another one out of the park!

  8. Joe, this is a great post.

    BTW, want a very disturbing image of what the year 2100 may bring us?

    That is what 5 degrees C may do.

    Scott A. Mandia, Professor of Physical Sciences
    Selden, NY
    My Global Warming Blog

  9. pete best says:

    Hmmmm, depressing really but also exciting for we have as yet only released enough CO2/GHG for a 1C temp rise and the race against time is now on. If humanity are reasonable enough and we are wise enough we can do something about it otherwise we might have am interesting 21st century.

  10. Susan Anderson says:

    Thanks for this. I will be stealing some quotes here.

    I thought the Lacis articles were terrific at the time, and am glad to see them as well. And Dr. Mandia is a long-time favorite, so I repost his link below:

    Speaking of scarifying images, many moons ago I found an illustrated article with graphics showing likely sea level rise of the more extreme sort – which I believe is what we are actually facing, as we see more an more examples like the floods in Oklahoma City, China, and Southern France.

    I was thinking someone should do “350 extreme events in 365 days” as a presentation, but am too lazy to do it myself.

  11. Susan Anderson says:

    re my comment #10, I forgot to ask if anyone knows where and could post the link to the article showing sea level rise – I think it was on the order of 20-30 feet.

  12. Phil Clarke says:

    >> “As it turned out, the list is both padded and laughable, containing the opinions of TV weathermen, economists, a bunch of non-prominent scientists who aren’t climate experts, and, perhaps surprisingly, even a number of people who actually believe in the consensus”

    A TV Weatherperson might plausibly be expected to have studied ‘aggregated weather’ aka climate at some point. There is rather less of an obvious justification for the inclusion of Alan Titchmarsh in inhofe’s list. He is a popular novelist and presenter of TV shows, especially Gardener’s World. By all accounts a thoroughly decent guy, he ain’t no ‘prominent scientist’, that’s for sure.

  13. Raul says:

    Simplifing the science.
    Certainly climate deniers will find a great
    simplification of the science involving
    the gulf of polution.
    For example due to health concerns not many
    scientists try to travel to unspeakably dangerous
    places only to study death.
    It was life and the promise of life that brought
    so much more knowledge as a result of past
    studies of the gulf and it’s intrakisys.
    Light is first and with it’s interaction with other
    things, conversions happen. It is now an extensive
    game change, because the type of life forms that
    like to eat oil , well such a large setback in the
    conversion processes when light reaches and
    interacts. The evolution processes within the
    gulf just start and stop to begin again.
    Our assurances of Natures grace seem far
    to the imaginary side of thought.
    Cause nature has laws that don’t seem
    to change. And going down the failed
    superhighway would still be bucking
    the way of life to evolve.
    So yeah it simplifys science cause so much
    progress of evolution just ain’t there.
    Simple math is easier than quantum physics.
    Looks like dead zone travels to the Atlantic.
    But it’s not completely dead just set back
    to an earlier stage of conversions, sort of,
    in areas and for longer time in spots.
    And climate deniers also actively or
    passively also resort to a lower level
    of conversion. Looking for the next
    best Jesus as a corelative lesson
    on the supiority of the modern ways?

  14. Susan,

    On my blog, I will be publishing a lengthy discussion on the impact of climate change on Sea Level Rise and the Coastal Environment. It should appear on Sunday. You can send me that link (mandias -at- and I may include it or you can post it as a comment on that thread.

    BTW, I do not hold a Ph.D. so it is not Dr. Mandia (but thanks for the promotion!) At SCCC, faculty can attain the rank of Professor with excellence in teaching, service to the College, service to the Community, and professional development. A Masters + 36 credits is also required.

    Scott A. Mandia, Professor of Physical Sciences
    Selden, NY
    My Global Warming Blog

  15. fj2 says:

    This is an excellent post by Joe which may be complemented by recent Scientific American and New Scientist issues focusing on the ultimate inclusiveness and anomalies of science and the groups of people that deny well-established reality-based ideas.

  16. Len Ornstein says:

    What are the roots of the divide between the AGW “consensus” and the skeptical “deniers”? Can the divide be bridged?

    Beginning near the turn of the 20th century, with the theoretical studies of Svante Arrhenius about how infrared absorbing gases help determine the surface temperature of the earth; then spurred by the reexamination of those models in the 1950’s, by Roger Revelle, and in the 1960’s, by Jule Charney; and then James Hansen’s modeling of the unique green-house-gas (GHG) induced forcing of the atmospheric temperature of Venus – climatologists and geophysicists began to further reexamine such models in greater detail. This was also strongly stimulated by Charles Keeling’s accumulating data of the steadily increasing concentration of well-mixed atmospheric CO2 at the Mauna Loa Observatory, beginning in 1958, at about 317 ppm (presently at about 390 ppm). It was quite clear that the CO2 concentration had been flat, at about 280 ppm for centuries (if not millennia) prior to the growing use of fossil carbon (coal, petroleum and natural gas) to fuel the industrial revolution. That CO2 record was the prototypical – and almost ‘noiseless’ – “hockey stick”.

    Although the theoretical models still leave uncertainty, particularly about the sign and magnitudes of the effects, on GHG feedbacks, of some low- and high-clouds, a consensus began to develop that risks of resulting increases in global temperature – and the risks associated with their possible consequences – deserved substantial increase in attention.

    Large efforts ensued to TRY to collect sufficiently unbiased, and statistically significant ‘other’ proxies for the hockey stick; global mean surface temperatures (GMST), ocean heat content (OHC), seal level rise (SLR), glacial ice-cores, sediment cores, tree-ring dendrology, etc. – all much noisier than the Keeling curve. The GMST trend for the last 40 or so years has converged to something like a mean of +0.2C/century, with considerable spread to the associated ‘95% confidence interval’. The others are not too out of line. And the increasingly more realistic (and more complicated) climate models are not ‘too’ far off either.

    There’s a general ‘feeling’ that such correlation of very different ‘kinds observations’ and models should help to build confidence above the level provided by each ‘independent’ data set, but so far, no good ‘statistical’ tools exist for ‘averaging’ such diverse results to get a ‘net mean and confidence interval’. In the breach, the current paradigm has developed to rely on the collective intuitions and confidence of those ‘experts’ who are judged to be most familiar with the data sets and with their relevance to related physical models.

    But even if the GMST trend were ‘only’ +0.1C/century, the associated risks would be only delayed by a ‘blink’ of geologic time – still demanding to be taken quite seriously!

    This certainly over simplifies things, but probably describes the root of the origins of the mainstream AGW ‘consensus’ – and of the current position of many ‘warmists’, and why they believe we must begin to seriously plan for the risks.

    Why is this so inimical to most skeptical “deniers’?

    Well, we have the record of ‘failed jeremiahs’:

    1) Robert Malthus, who at the end of the 18th century, published his simple but penetrating theoretical econometric model, “An Essay on the Principle of Population”, that has turned out to have been ‘off’ in the timing of its predictions (but I believe, probably is about ‘correct’ in predicting what we must expect, if some appropriate changes in human behavior fail to accommodate – ‘in time’ – to the reality of the finite resources of our planet); and

    2) the predictions of the Club of Rome’s 1972, “The Limits to Growth”, that also have proven to have been somewhat premature.

    And the IPCC was supposed to adhere closely to the (impossible?) charge to be “policy relevant” rather than “policy prescriptive”!

    The perceptions of just where science fits – in the spectrum of beliefs – differ among policy makers, the general public – and, to some extent, even among scientists – and this has to contribute a great deal of the resulting dissonance.

    Further, it certainly doesn’t help that many believe motivation for science, does and should stem from values derived from Golden Rules, while others, e.g., Positivists, insist (I argue, incorrectly) that science can, and should, be freed from all such metaphysical baggage ;-)

    I believe these unpleasant pieces of the puzzle need to be fit in place in order to understand the apparent irrationality of the position of many ‘honest’ “deniers”.

    For further ‘clarification’ of these latter points, see:

    “The Sceptical Scientific Mind-Set in the Spectrum of Belief: It’s about models of ‘reality’ – and the unavoidable incompleteness of evidence, for – or against – any model”.

  17. Chris Winter says:

    I feel the most concise way to describe it is that the Denialists conflate scientific consensus, which depends on recognizing facts, and political consensus, which depends on agreeing to work for some goal.

    I explain in more detail in item 3, here:

  18. Chris,

    Very nice discussion on your blog. I have bookmarked it and will give it a thorough read soon.

    You may be very interested in these two posts regarding grant funding:

    1) Taking the Money for Grant(ed) – Part I

    2) Taking the Money for Grant(ed) – Part II

    Scott A. Mandia, Professor of Physical Sciences
    Selden, NY
    My Global Warming Blog
    Twitter: AGW_Prof