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.
- U.S. National Academy of Sciences labels as “settled facts” that “the Earth system is warming and that much of this warming is very likely due to human activities”
- 1700 UK scientists come forward to reaffirm climate science
- 255 National Academy of Sciences members, including 11 Nobel laureates, defend climate science integrity: “There is compelling, comprehensive, and consistent objective evidence that humans are changing the climate in ways that threaten our societies and the ecosystems on which we depend.”
- American Meteorological Society reaffirms “that the atmosphere, ocean, and land surface are warming; that humans have significantly contributed to this change; and that further climate change will continue to have important impacts on human societies”¦.”
- The American Association for the Advancement of Science reaffirms “The scientific evidence is clear: global climate change caused by human activities is occurring now, and it is a growing threat to society.”