Later On

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The scientific consensus on global warming

with 11 comments

From the American Association for the Advancement of Science (AAAS), the preeminent scientific organization in the US. Note that this article is not based on a mere count of articles, but rather looks at statements from various scientific organizations.

Science 3 December 2004:
Vol. 306. no. 5702, p. 1686
DOI: 10.1126/science.1103618

The Scientific Consensus on Climate Change

Naomi Oreskes*

Policy-makers and the media, particularly in the United States, frequently assert that climate science is highly uncertain. Some have used this as an argument against adopting strong measures to reduce greenhouse gas emissions. For example, while discussing a major U.S. Environmental Protection Agency report on the risks of climate change, then-EPA administrator Christine Whitman argued, “As [the report] went through review, there was less consensus on the science and conclusions on climate change” (1). Some corporations whose revenues might be adversely affected by controls on carbon dioxide emissions have also alleged major uncertainties in the science (2). Such statements suggest that there might be substantive disagreement in the scientific community about the reality of anthropogenic climate change. This is not the case.

The scientific consensus is clearly expressed in the reports of the Intergovernmental Panel on Climate Change (IPCC). Created in 1988 by the World Meteorological Organization and the United Nations Environmental Programme, IPCC’s purpose is to evaluate the state of climate science as a basis for informed policy action, primarily on the basis of peer-reviewed and published scientific literature (3). In its most recent assessment, IPCC states unequivocally that the consensus of scientific opinion is that Earth’s climate is being affected by human activities: “Human activities … are modifying the concentration of atmospheric constituents … that absorb or scatter radiant energy. … [M]ost of the observed warming over the last 50 years is likely to have been due to the increase in greenhouse gas concentrations” [p. 21 in (4)].

IPCC is not alone in its conclusions. In recent years, all major scientific bodies in the United States whose members’ expertise bears directly on the matter have issued similar statements. For example, the National Academy of Sciences report, Climate Change Science: An Analysis of Some Key Questions, begins: “Greenhouse gases are accumulating in Earth’s atmosphere as a result of human activities, causing surface air temperatures and subsurface ocean temperatures to rise” [p. 1 in (5)]. The report explicitly asks whether the IPCC assessment is a fair summary of professional scientific thinking, and answers yes: “The IPCC’s conclusion that most of the observed warming of the last 50 years is likely to have been due to the increase in greenhouse gas concentrations accurately reflects the current thinking of the scientific community on this issue” [p. 3 in (5)].

Others agree. The American Meteorological Society (6), the American Geophysical Union (7), and the American Association for the Advancement of Science (AAAS) all have issued statements in recent years concluding that the evidence for human modification of climate is compelling (8).

The drafting of such reports and statements involves many opportunities for comment, criticism, and revision, and it is not likely that they would diverge greatly from the opinions of the societies’ members. Nevertheless, they might downplay legitimate dissenting opinions. That hypothesis was tested by analyzing 928 abstracts, published in refereed scientific journals between 1993 and 2003, and listed in the ISI database with the keywords “climate change” (9).

The 928 papers were divided into six categories: explicit endorsement of the consensus position, evaluation of impacts, mitigation proposals, methods, paleoclimate analysis, and rejection of the consensus position. Of all the papers, 75% fell into the first three categories, either explicitly or implicitly accepting the consensus view; 25% dealt with methods or paleoclimate, taking no position on current anthropogenic climate change. Remarkably, none of the papers disagreed with the consensus position.

Admittedly, authors evaluating impacts, developing methods, or studying paleoclimatic change might believe that current climate change is natural. However, none of these papers argued that point.

This analysis shows that scientists publishing in the peer-reviewed literature agree with IPCC, the National Academy of Sciences, and the public statements of their professional societies. Politicians, economists, journalists, and others may have the impression of confusion, disagreement, or discord among climate scientists, but that impression is incorrect.

The scientific consensus might, of course, be wrong. If the history of science teaches anything, it is humility, and no one can be faulted for failing to act on what is not known. But our grandchildren will surely blame us if they find that we understood the reality of anthropogenic climate change and failed to do anything about it.

Many details about climate interactions are not well understood, and there are ample grounds for continued research to provide a better basis for understanding climate dynamics. The question of what to do about climate change is also still open. But there is a scientific consensus on the reality of anthropogenic climate change. Climate scientists have repeatedly tried to make this clear. It is time for the rest of us to listen.

References and Notes

  1. A. C. Revkin, K. Q. Seelye, New York Times, 19 June 2003, A1.
  2. S. van den Hove, M. Le Menestrel, H.-C. de Bettignies, Climate Policy 2 (1), 3 (2003).
  3. See
  4. J. J. McCarthy et al., Eds., Climate Change 2001: Impacts, Adaptation, and Vulnerability (Cambridge Univ. Press, Cambridge, 2001).
  5. National Academy of Sciences Committee on the Science of Climate Change, Climate Change Science: An Analysis of Some Key Questions (National Academy Press, Washington, DC, 2001).
  6. American Meteorological Society, Bull. Am. Meteorol. Soc. 84, 508 (2003).
  7. American Geophysical Union, Eos 84 (51), 574 (2003).
  8. See
  9. The first year for which the database consistently published abstracts was 1993. Some abstracts were deleted from our analysis because, although the authors had put “climate change” in their key words, the paper was not about climate change.
  10. This essay is excerpted from the 2004 George Sarton Memorial Lecture, “Consensus in science: How do we know we’re not wrong,” presented at the AAAS meeting on 13 February 2004. I am grateful to AAAS and the History of Science Society for their support of this lectureship; to my research assistants S. Luis and G. Law; and to D. C. Agnew, K. Belitz, J. R. Fleming, M. T. Greene, H. Leifert, and R. C. J. Somerville for helpful discussions.

UPDATE: An interesting chart:


Global warming slowed a while, due to the eruption of Mt. Pinatubo, which provided a shield against solar warming—a temporary shield, unfortunatley. Details here.

UPDATE: Responses to the most common skeptical arguments against global warming is a useful compendium, worth browsing.

Written by Leisureguy

4 September 2007 at 7:51 pm

11 Responses

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  1. This is the older study that was referenced in my previous post. And the article referenced in my previous post updates Oreskes’ 2004 study to conclude that the apparent consensus is unraveling as more and more scientists either refuse to hop onto the global warming bandwagon or actively challenge it. What is happening is global warming is what basic economics would predict — the pool of applicants for scientific grants to study (and confirm) global warming has grown because of the vast resources being funnelled to such studies by legislatures. This attracts greater numbers of scholars to the point that the competition weakens the quality of the product and/or saturates the market for grant money to prove global warming. Other scholars seeking to differentiate themselves for the purpose of justifying new grants can do so by maintaining sharp neutrality or challenging the prevailing global warming hypothesis. The latter activity is exactly what scientists, as opposed to politicians, are supposed to do–challenge, question, test, and alter hypotheses to fit existing facts, not existing political opinions.

    Overall, I’m relatively thankful to Al Gore for providing global warming with its “jumping the shark” moment. On the other hand, in 20 years we’ll have forgotten global warming as we all shiver and wait for the next ice age. Or if global warming is real–anthropogenic or not–we’ll be sitting pretty in a world that is far better suited to feeding the projected 9 billion people in 2050 because, as past warming periods have demonstrated, greater warmth equals more food.



    5 September 2007 at 6:06 am

  2. The study you referenced has not been published in any peer-reviewed journal, and so far as I can tell is an article-count, nothing more. Orekes’s study includes statements made by leading scientific organizations that global warming is happening and is anthropogenic. That is, it includes conclusions of the major scientific organizations.

    Whether global warming is anthropogenic (as is the consensus) or not, BTW, is a scientific opinion, not political.

    Not sure where the “next ice age” comment comes from. According to a recent article in New Scientist:

    THE fossil fuels we burn today may leave an atmospheric “hangover” lasting hundreds of thousands of years, which may cause enough residual warming to prevent the onset of the next ice age. This is the most far-reaching disruption of long-term planetary processes yet suggested for human activity.

    The UN’s Intergovernmental Panel on Climate Change describes carbon dioxide as having a lifetime in the atmosphere of between five and 200 years before it is ultimately absorbed by the oceans. In fact, as much as one-tenth of the CO2 we are emitting now will linger in the air for at least 100,000 years, and perhaps much longer, says Toby Tyrrell of the UK’s National Oceanography Centre in Southampton.

    “It is often assumed that the Earth will always recover from perturbations. But our research shows that it doesn’t necessarily behave like this,” says Tyrrell. “It isn’t always inherently self-rectifying.”

    If global warming turns the American Midwest in another dust bowl through disruption of rain cycles, I think that the increased food supply you are suggesting may not occur. Not to mention other natural disasters such as the loss of all low-lying land, the growth of desert areas, loss of species (particularly fauna), and the like.

    I don’t think past warming periods will hold a candle to what we’re going to experience—those did not lead to the melting of the Greenland icecap and (if it happens) to the thawing of Antarctica.



    5 September 2007 at 9:10 am

  3. I’m not an insider here and know very little on the subject. Having said that I think my question is important and should be seriously considered. My question s simple, “What happens if you are wrong”?


    Edwin C. King

    24 June 2014 at 8:01 am

  4. Exactly: if essentially all the climatologists in the world are wrong, and we stifle carbon emissions by developing clean energy sources and cutting back in other ways, what is the damage? Some money is spend on some things rather than others, with the overall impact being modest.

    Now compare that to the damage done if the world’s climatologists are correct and those who know little or nothing about science are wrong—that is, if our releasing millions of tons of carbon (and now methane, from thawing tundra) into the air does indeed cause global warming (as has been known from the 19th century: it’s not a controversial idea in science that greenhouse gases cause warming). If we continue as we are, we won’t spend so much on renewable energy, and the warming climate will result in ocean-level rise, displacing millions, cause crop losses (and less nutritive value in the crops that survive), with food crises leading to wars and famine. With a rise of around 6ºC, the area of the globe between the tropics would become uninhabitable. This does not even consider the side effects (e.g., mass extinctions) that we are starting to recognize only after they occur. And because the CO2 (and methane and whatever) are already then in the atmosphere, it will be impossible to reverse course.

    It’s as if your doctor told you that might have a type of cancer that is extremely deadly, but the treatment, though not terribly costly, would involve some lifestyle changes but would also offer very good odds of curing the cancer. But because that would be inconvenient for you, the doctor recommends that you continue as before, because in a year or so, it will be perfectly clear whether you have the cancer or not. (Unfortunately, at that point, no treatment will be effective and you will die.) What would you do?



    24 June 2014 at 10:30 am

  5. Two logical fallacies are committed here:
    1. Bandwagon Fallacy: “95% of climate scientists agree global warming is caused by humans”
    Note: that IPCC U.N. report only had 3,146 respondents to a 2 question online survey. Only 77 were climate scientists, of the 77 only 75 agreed global warming was caused by humans (thats how thwy got the 75%!)

    2. Appeal to Emotion: “What if we climate deniers are wrong?”

    This is why many are skeptical of man made global warming” and the coming global carbon tax that will weaken sovereignty of individual countries.



    1 December 2015 at 9:36 pm

  6. What you call “appeal to emotion” I see as evaluating the relative risks of doing nothing (and being wrong) compared with finding a way to reducing carbon emissions drastically (and being wrong). In other words, it is not in the least an appeal to emotion, but rather the assessment of risk of an erroneous judgment in each case.

    Being wrong in the first instance would be an existential catastrophe (the beginnings of which we already see: more frequent flooding of low-lying coastal places as ocean levels rise, increasing food shortages in some countries due to changes in weather patterns, more frequent massive rains causing “hundred-year floods” and in general more frequent instances of extreme weather, and so on).

    Being wrong in the second instance would be irksome, but on the other hand would offer business opportunities in developing new technologies.

    The Marshall Islands certainly find that the rising ocean levels are a threat to their sovereignity greater than a tax would be: see this article in today’s NY Times.

    At any rate, my experience with climate change denialists is that reasoned arguments based on evidence have no effect, since the position they hold is based on some sort of faith and not on evidence—indeed, their position depends heavily on ignoring evidence.

    Still, two-thirds of the American public support taking action to mitigate and indeed reverse climate change.

    And take a look at this article as well.

    If you are in fact open to learning more about climate change, the NY Times has a column today that will help: “Short Answers to Difficult Questions About Climate Change.” Here’s one of the short answers from that article:

    Most of the attacks on climate science are coming from libertarians and other political conservatives who do not like the policies that have been proposed to fight global warming. Instead of negotiating over those policies and trying to make them more subject to free-market principles, they have taken the approach of blocking them by trying to undermine the science.

    This ideological position has been propped up by money from fossil-fuel interests, which have paid to create organizations, fund conferences and the like. The scientific arguments made by these groups usually involve cherry-picking data, such as focusing on short-term blips in the temperature record or in sea ice, while ignoring the long-term trends.

    The most extreme version of climate denialism is to claim that scientists are engaged in a worldwide hoax to fool the public so that the government can gain greater control over people’s lives. As the arguments have become more strained, many oil and coal companies have begun to distance themselves publicly from climate denialism, but some are still helping to finance the campaigns of politicians who espouse such views.



    2 December 2015 at 7:32 am

  7. ” Bandwagon Fallacy: “95% of climate scientists agree global warming is caused by humans””

    The fault of this comment is it assumes that the point of the consensus is to prove global warming is true. To the contrary, the fact of global warming stands as proven on the basis of empirical evidence alone. It is further demonstrated as true based on centuries of sound scientific theory of chemistry, thermodynamics, spectrography, quantum mechanics, and more. Even further, the basics of this wealth of science and empirical data is supported by thousands of laboratory experiments.

    The fact is that when sound science is presented in the journals, a consensus forms around it. Before 1913, there was a scientific disagreement on the nature of matter. There was no consensus on whether matter consisted of discrete particles or was smooth. It was Einstein’s experiments and paper on Brownian motion that proved matter consisted of discrete particles that is now accepted as atoms and molecules. This proof was not immediately accepted as fact but absorbed into the body of science over time. And in doing so, a consensus formed. In doing so, the understanding of the science of thermodynamics changed, resulting is what is now statistical thermodynamics. Every physicist does not repeat Einstein’s experiment. It is the consensus of lectures, publishers, experimenters and theorists in the field of physics, as well as the understanding that that consensus is grounded in the scientific method, that is the signal which let’s new scientists move forward. No scientist has to reinvent the wheel.

    While every scientist could redo 400 years of science, it is simply impractical and foolish to do so. And it is an absurd expectation that every political leader, historian, reporter, financial investor, or member of the general public should repeat 400 years of scientific discovery and experimentation in the pursuit of their goals. It is the general knowledge that ““95% of climate scientists agree global warming is caused by humans””” which provides the signal needed to move forward with their projects.



    5 March 2016 at 3:16 pm

  8. When hiking in the woods with friends, and someone yells “Bear” and runs, the smart decision is to jump on that bandwagon.



    5 March 2016 at 3:28 pm

  9. Sounds like China better get its act together and save our planet!



    27 July 2016 at 4:39 pm

  10. Sounds like when your house is on fire, it doesn’t matter if you threw the cigarette or your neighbor. Get a bucket and start throwing water on it and organize. how was the flight to hawaii?



    27 June 2021 at 10:07 pm

  11. This post by Rebecca Solnit quotes Bill McKibben on the dangers of climate change to humans.

    We were not built for this heat, writes Bill McKibben: I happened to be talking with Dr. Rupa Basu, the chief of air-and-climate epidemiology at California’s Office of Environmental Health Hazard Assessment, on Friday, a day after Palm Springs had tied its all-time heat record with a reading of a hundred and twenty-three degrees Fahrenheit. That’s hot—hotter than the human body can really handle. The day before, with temperatures topping a hundred degrees before noon, a hiker in the San Bernardino National Forest had keeled over and died. “We talk a lot about biological adaptability, but as humans we’re not supposed to adapt to temps that high,” Basu said. “If your core body temp reaches a hundred and five, that means death can be imminent. As humans, we can only adapt so much. Once the air temperature is above a hundred and twenty, there’s only so much you can do, except rely on air-conditioning and other mitigation strategies. And that puts a lot of pressure on the power grid, and that could result in brownouts and blackouts. It’s not really a long-term, chronic solution. It’s just living for the moment and hoping it works.”

    And often it doesn’t work. Last summer, Basu published a remarkable paper, a “systematic review” of research on pregnant women. The studies she looked at—which collectively examined more than thirty-two million births—found that higher temperatures in the weeks before delivery were linked to stillbirths and low birth weights. “It’s weeks thirty-five and thirty-six that seem to be the trigger,” she told me recently. “What we think is happening is that a lot of the mechanisms from heat-related illness start with dehydration. If there are symptoms of dehydration, those might be overlooked. If someone doesn’t connect it with heat, they might not get to a cooler environment. You see vomiting—and people might say, ‘That’s O.K. Bound to happen when you’re pregnant.’ But it’s because of the dehydration.” Further along in the pregnancy, she said, “your body releases oxytocin, which triggers contractions. And if it happens prematurely—well, heat raises the level of oxytocin faster. If you’re not able to thermoregulate, get the temp down, it can trigger low birth weight or, earlier on, miscarriage or stillbirth.” Past a certain point, the body diverts blood flow to the subcutaneous layer beneath the skin, where the body’s heat can radiate out into the air. That diverts the blood “away from vital organs,” Basu said. “And away from the fetus.”

    The brain is an organ, too. For all its metaphysical magnificence, it’s a hunk of cells that comes with operating specs. Again, don’t let its temperature get too high: in 2018, Basu published a study showing the effect of seasonal temperatures on mental health. A ten-degree-Fahrenheit jump in temperature during the warm season was associated with an increase in emergency-room visits for “mental-health disorders, self-injury/suicide, and intentional injury/homicide” of 4.8, 5.8, and 7.9 per cent, respectively. Those are big numbers, and the search for mechanisms that explain them is fascinating. Among other things, certain medications impede the body’s ability to thermoregulate: beta-blockers, for instance, decrease the flow of blood to the skin, and antidepressants can increase sweating, Basu told me. “There’s also some evidence to show that heat affects neurotransmitters themselves—that everything is just a little bit slower.”

    Both these effects show up more strongly in this country in Black and Hispanic patients—probably, as Basu explained, because those groups disproportionately live in low-income neighborhoods. “They’re often in areas where there are more fossil-fuel emissions, fewer green spaces, and more blacktop and cement, which really absorbs and retains the heat,” she said. “And also living closer to freeways. That exacerbates air pollution. And, with the heat, that’s a synergistic effect. It’s environmental racism that leads to these differences in exposure.” Some people, she added, bristle at hearing that: “Someone said to me, ‘Oh, so now we’re breathing different air?’ And I said, ‘Yes, that’s exactly right. We can track it down to the Zip Code level.’ ” Call it critical race epidemiology.

    Which leads us, of course, back to politics. There’s only so much that doctors can do to help us deal with heat; ultimately, it’s up to the Joe Bidens and the Joe Manchins—and the Xi Jinpings—of the world. “We’re seeing these kinds of extreme temperatures in Palm Springs right now,” Basu said. “If we start to see those in more populated areas, imagine the public-health impact.” That’s obviously what’s coming. Last week, researchers at nasa and noaa found that, according to satellite data, “the earth is warming faster than expected” and that the planet’s energy imbalance—the difference between how much of the sun’s energy the planet absorbs and how much radiates back out to space—has doubled since 2005, an increase equivalent to “every person on Earth using 20 electric tea kettles at once.” And the National Weather Service is forecasting a heatwave this week for the Pacific Northwest that could smash regional records.

    Amid the endless deal-making—the U.S. last backed off what would have been a G-7 plan to end coal use—the human body is a useful bottom line. “I think what we need to do is prevent the warming,” Basu said, when I asked her for a prescription. “So it doesn’t get that hot.”



    28 June 2021 at 5:36 am

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