Atmospheric Sciences Editors' Vox

Responding to Climate Change Deniers with Simple Facts and Logic

A sequence of five questions and answers that can be used by scientists to communicate some simple concepts of climate change to broader audiences.


Many of our colleagues, and concerned citizens, have asked how to respond to climate contrarians who claim that they don’t “believe” in climate change, or have fallen prey to disinformation publicized by those with vested interests in fossil fuels and related industries. In some cases, simple facts and logic can help such people understand the realities of the earth system and how it is responding (and will respond further) to anthropogenic perturbations such as greenhouse gas emissions.

However, there are many others for whom this approach proves ineffective. Holding a worldview that would seem anathema to any scientist, many of our fellow citizens do not use direct observation, evidence, or science in general, as their primary basis for decision-making. No amount of factual education can alter this worldview, and it has become clear that other means must be found to prevent this segment of the population from making self-harming decisions, whether induced by disinformation or otherwise.

Some of these issues were articulated in a special session at the recent AGU meeting on Climate Literacy. In one presentation, Naomi Oreskes suggested that the human brain’s decision-making centers are more closely related to emotional centers than they are to rational thought and reasoning, citing the 19th century “miracle” case of Phineas Gage as a rare example of the link between emotions and decision-making. While people do not typically have iron rods driven through their heads, this further supports the general theme that emerged from the AGU session that a significant segment of the population will respond better to emotional messages than to factual information. As a scientific community, we are a long way off from being able to communicate on that level, yet it appears that a way must be found.

Meanwhile, for those who may respond to a logical sequence of reasoning, the following questions should be asked and answered in sequence. Hopefully this can assist the scientific community in communicating some simple concepts to broad audiences.

1.  Is climate changing?

Yes. Scientific observations and measurements have provided undeniable data that show temperatures have been rising, precipitation patterns have been changing, and ocean and atmospheric circulation systems have been changing throughout the 20th and 21st centuries.

2. Do people have anything to do with it?

Yes. Greenhouse gas emissions (primarily carbon dioxide from fossil fuel burning) have to warm the atmosphere—it is what they do. The consensus of model results shows that the global climate is sufficiently sensitive to historic anthropogenic carbon dioxide emissions to have already warmed by the amount measured over the last 150 years. In addition, carbon dioxide triggers a water vapor feedback, greatly amplifying the effect, as warm air can hold more water vapor than cold air.

3. Is climate change bad?

Yes. While this is a more normative question to be considered by philosophers and the general public rather than by scientists, history has shown that any change in the environment of stable civilizations is disruptive to those civilizations. Alterations in areas in which crops can be grown, changes in phenology (when plants bloom or flower, when leaves fall, when insects emerge, etc.), shifting storm tracks, and rising sea level may have devastating economic, social, and political consequences on modern societies.

4. Can we do anything about it?

Yes. Because much of the warming caused by past emissions has already occurred, cessation of emissions can stabilize climate in the 21st century. Until they are overwhelmed, natural carbon sinks in the ocean and terrestrial ecosystems can continue to absorb previously emitted carbon and return global climate to the stable state in which civilization evolved over the last 10,000 years.

5. Is it worth doing anything about?

Yes.  Economic analyses indicate that the cost of adaptation to climate change in the form of agricultural disruptions, damage to coastal cities and infrastructure, and impacts of extreme events will be much greater than the cost of mitigation by transition to sustainable energy sources.

What we learn from the past is that nearly every major climate change in Earth’s history has been accompanied by changes in greenhouse gases, with warming associated with more carbon dioxide and cooling associated with less. In the geologic past, before humans existed, climate and atmospheric carbon dioxide concentrations varied together, with carbon dioxide change not always predating climate change. This was due to the runaway feedbacks between temperature, carbon dioxide in the atmosphere and ocean, and water vapor in the atmosphere. However, now that we have devised a way to inject carbon dioxide directly into the atmosphere (fossil fuel burning), carbon dioxide is preceding climate warming, which is already responding to the additional greenhouse gases.

–Dork Sahagian, Department of Earth and Environmental Sciences, Lehigh University; email: [email protected]

  • PeterC

    Simply stating, as in #2, that people have something to do with changing climate does not make it so.

    As for greenhouse gases, ALL gases in the atmosphere are greenhouse gases as they all absorb heat one way or another. Therefore, CO2, as a very minor component (as is methane), has a very minor effect upon climate changes.

  • Afroz Ahmad Shah

    Dear author,
    As a researcher I feel compelled to say that somehow we are still not sure how to compare the present atmospheric composition with that of early earth (e.g. Hadean and Archean). So I feel the question is not just about denial it is more about how we put things together in perspective. The public needs numbers and we ought to show them.
    No doubt a larger number of serious scientific works have established that increasing levels of atmospheric carbon dioxide gas over the decades have caused increase in temperature, and how much is that variation (~2°). And I think we all agree that early earth had much higher concentration of carbon-dioxide, and how we got where we are now is still vigorously debated, as evidence are settle. Plus the fact that carbon-dioxide is not the only driver of climate, and if we discuss its role, then obvious questions will be asked. This becomes obvious when we look at the composition of the air that we breathe. It mainly contains nitrogen (~76%) and oxygen (~21%). The concentration of carbon dioxide is just ~0.038% and the first two major gases in our atmosphere are NOT greenhouse gases, which means that there concentration has probably little to no effect on warming of the atmosphere. And the role of Sun, which is central to the existence of life on the earth as it provides heat that is required to keep the temperature and atmospheric circulation in balance. So the small amount of greenhouse gases (mainly water vapor, and little of CO2) traps (absorb and re-emit) the infrared radiation, increasing the temperature of the atmosphere. Again we need to look how concentrations of water vapor (the major greenhouse gap in our atmosphere) have changed over the geological time, and compare it with Holocene, that may give us some idea how it plays a role. Similarly we have to map the variations of clouds, the condensed form of water vapor, over the centuries or more to accurately map and understand the role in atmospheric composition, temperature etc. And we know that volcanic eruptions contrinute about 1% to the total CO2 budget, and thus this needs to be shown to the public. Apart from this there are also small percentage of naturally occurring other greenhouse gases in the atmosphere, which includes methane and nitrous oxide. And humans has also contributed some new varieties of synthetic greenhouse gases, which include chlorofluorocarbons (CFCs), hydrofluorocarbons (HFCs) and Perfluorocarbons (PFCs), as well as sulfur hexafluoride (SF6). These gases have also influenced the temperature structure of our atmosphere over the decades of industrial revolution on the planet.
    So I think here we are: the present concentrations of gases in our atmosphere are both natural and man-made. The contribution of each gas in modifying the concentration of greenhouses gases in our atmosphere is still vigorously debated, and most of the scientists agree that anthropogenic CO2 is the major contributor, but we are yet to solve the problem over the geological timescale. However, humans ought to be responsible not to aggravate the obvious problems that we are facing right now, and must workout solution for a better future. Please remember that Earth is a delicate system of systems, and we are part of it, any of our wrong actions can alter its delicate balance, which will ultimately destroy life, including us.

  • Ronal Larson

    How about an approach that is questioning – why should we allow China to take the present US climate lead? (as they have for all the renewables). This seems different than introducing a scare – which we are advised is not effective.

    • 9.8m/ss

      Questioning can not challenge a deeply held belief system. Whether there’s any evidence for that belief system is irrelevant. The person who lives in the Fox-Brietbart alternative universe has answers to all your questions. The Chinese are lying about their advances in renewable energy. They’re secretly building nine new multi gigawatt coal plants each week, and only pretending to retire the old ones, because they know AGW is a hoax and coal is the future! The solar panels they sell us are sabotaged and will wear out in three years. But, more centrally, the belief system is immunized against any facts which contradict it. They’re all inventions of the liberal conspiracy to destroy America!

      Recently I’ve been seeing advertisements for residential PV systems which seem to acknowledge the problem the Fox-Brietbart mythology presents. They imply that the power company is part of the government and the liberal conspiracy, and you can stick it to the man by getting off the grid. They carefully avoid mentioning the environmental benefits of converting to solar energy.

  • Andrew Chermak

    A good article. It might be helpful to mention some of the sources of natural variation in greenhouse gases over geologic time and cite some specific numerical examples of what we know about temperature and precipitation variations that resulted from those natural inputs and how they compare with recent anthropogenic shock inputs. Even relatively non-scientific people can understand the numbers.

    One observation might be better not stated, or at least stated differently, the part that says “………No amount of factual education can alter this worldview, and it has become clear that other means must be found to prevent this segment of the population from making self-harming decisions, whether induced by disinformation or otherwise.”. We all get frustrated by people who simply refuse to see things our way but the implications of “other means must be found” are truly frightening to contemplate.

    • Thomas H Pritchett

      I have made it a point to be active on social media such as Facebook and to have as wide of group of friends in terms of political beliefs. Therefore, I have friended not only colleagues and others who share my views on climate but also high school classmates and people I have encountered in hobby, Civil War Reenacting. I have made it a point to never remove anyone from my Friends list because of their political views and have tried to only engage them respectfully in disagreements. Another thing, I find that most scientists tend to avoid interacting with local groups who are working to make changes in the political will for dealing with climate change. I know that we are all busy but there are groups out there who could use our expertise. Personally, I have become active in the Citizen’s Climate Lobby but there are others of a similar nature out there. Furthermore, I would suggest that we could become more active in engaging the public with well thought out Op-Eds and Letters to the Editors at our local newspapers.

  • philippe vidon

    The rationale behind this short article makes no sense whatsoever. Is AGU and most of its scientists so narrow minded that they still believe that facts will lead people to change their mind? Human beings are irrational by nature and emotional. Further, simplifying climate change like it is done in the article above, and speaking in terms of absolute truth is the first mistake in this article. Currently, the rhetoric around the concept of climate change has become so simplified that it is basically wrong. I agree that the burning of fossil fuels is causing warming, but considering that we can probably all agree that we still poorly understand climate (e.g. el Niño), bringing it down to just controlling emissions is really a problem. We know from recent research that people’s worldviews have more impact on the perception of climate change than any data a scientist can publish. As long as AGU keeps pushing for an overly simplistic view of climate change and ignores how people develop opinions, we won’t go very far in convincing the world that climate change is a problem.

  • tolo4zero

    If anyone questions anything at all about the Catastrophic Anthropogenic Global Warming scare, they are considered climate change deniers.
    This is not science but a religion.

    • drklassen

      Yes, climate change denial is religion, not science.

      • Dick Rasmussen

        Those are all good reasons ! — But I very much doubt you are going to convince people with this type of article even as true as it is. I look at climate warming simply by the industrial revolution 1850 to the present along with the population growth in that time and the development of all the countries in the world in that time. To me it is simple logic that it couldn’t be anything else.
        If folks don’t want to accept that there are not any magic words that will convince them. But I’ll keep trying !

    • 9.8m/ss

      What makes you think so? Most areas of science are too competitive for a scientific religion contrary to evidence to survive. How is that competition suppressed in the climate related sciences? Who’s organizing the suppression? Why are they doing it?

  • Spencer Weart

    Unfortunately, stating true facts is useless unless your audience believes that you are a credible source of information. Your audience has probably heard the exact opposite statements (humans are not responsible, mitigation is too costly, etc.) from sources they may trust more — certain politicians, Fox News, the Wall St. Journal, etc. Thus the essential first step is to establish your credibility. Just being a scientist does not automatically make you credible; it may even make you suspicious. So you need to show that you understand and sympathize with your audience’s world-view, that you are describing a near-universal consensus of genuine experts, etc. (It may also help to undercut the credibility of our opponents by emphasizing their financial and ideological interests in denial.)

    • David Huard

      I would argue strongly against attacking your opponent’s credibility in a debate. I find the best way to establish credibility is not to emphasize your scientific credentials, but to behave like a nice, reasonable and empathic person. Accusing someone of having undisclosed, vested interests is perceived as mean by a neutral public and undercuts your own credibility. I find it much more effective to discuss the cognitive biases that we all have, and how to avoid being tricked by them. In other words, make these discussions about “How to think like a scientist”, and let people reach their own conclusions.

      • Spencer Weart

        That sounds right. I certainly wouldn’t attack another individual directly, but in speaking generally I think the work by Oreskes et al. exposing the financial links of deniers can be useful.

        • David Huard

          Agreed. I also like to use concepts from “Scientific Certainty Argumentation Methods (SCAMs): Science and the Politics of Doubt” by Freudenburg at al. to discuss these issues.

        • Paul Ruscher

          This has been helpful apparently in places where carbon disinvestment discussions have taken place. I try to be respectful and factual always and don’t like using denialist and alarmist labels

    • DHClark

      I agree that establishing your credibility is crucial to getting people who are on the fence (or even more so, those who are antagonistic towards climate science) to listen. One of the more effective tools I’ve used in public discussions is to diffuse the notion that climate scientists are basically being “bought off” in seeking funding (i.e., we’re just toeing the line on climate change to get grants or pubs). I use a few lines of reasoning: 1) active scientists are, by nature, a contentious bunch and that we get funding (and whatever fame is possible) not by toeing the status quo, but by showing that the status quo is wrong. We’d all LOVE to be the one to show AGW is wrong, but rigorous studies repeatedly reinforce the basic principles in the IPCC. 2) I dispel the notion of being in it for the money by walking through the breakdown of an NSF climate change grant I received recently (ice coring); the total amount looks really big (100’s of thousands), but only part of that comes to my university (rest to other PI’s); of the part coming to my university (still a lot), most is for subcontractors (helicopters, equipment, field expenses etc.) and indirect costs. It’s also spread over 4 years Of the remainder, most of the salary goes to grad student RA’s and analyses. Boiling it down to any funds I would actually see as salary, it amounts to a few thousand a year. I ask the audience how many of them would go against their core beliefs for that small amount. Most folks have no idea that research grants work that way…they have a sense that the PI’s just get a big check and can go do what they want with it. It really is a surprise that such a big grant amounts to so little in my own bank account.

      • Ben

        Engaging with the public in this way is sorely lacking. I find it is not supported very well by scientific institutions in reality. I get pressure from my seniors to deliver research and publish but very little encouragement to communicate with the public. And if I can get out to communicate, being in California, I am simply “preaching to the converted”.

        The real challenge is mobilising science in areas that are more traditional or isolated, and on a scale that will have real impact. I think the challenge is enormous, not least because of the points raised in the original article. Many people are so tied to their (mis-informed) views, and perhaps scared of the reality and having to actually do something, or sacrifice something, that *any* approach based upon logical argument (like establishing the credibility of your source) is futile. It is equivalent to shouting at the television.

        I have been talking with friends and colleagues about how to approach this problem. I don’t have any immediate answers, but I have some ideas about putting more of a human face on the voice of science – a very large project involving hundreds or even thousands of international scientists being seen and heard in an emotional (or at least more human) way, might have an impact. (As opposed to publications, offical reports, IPCC, the occasional letter to congress etc).

        I think until there is a focus on more aggressive outreach in places that matter, and on a scale that makes a difference, we are fighting a losing battle.

        • Thomas H Pritchett

          See my reply to Andrew Chermak in terms of how to mobilize science. However, I agree with your last sentence that we are currently fighting a losing battle. However, I believe it is not because the fight is unwinnable but because we are allowing the other side to dictate how the battle is to be fought and they are taking advantage of our seeming unwillingness to come out our academic shells and directly engage the public via social media and other non-academic venues. In fact, I would suspect that many of us may subconsciously look down out our colleagues who do. We all know that Dr. Hansen has become a very public advocate towards addressing climate change but I wonder how many of us feel that he may have cheapened himself as a scientists for acting in this manner; I know that I have had to fight that impulse when I saw his name on his most recent publication. Furthermore, I suspect that I am not the only one here who may have had brief, but totally unjustified, thoughts along this line.

      • 9.8m/ss

        When I told my scientist friends what I heard on Fox and read on Breitbart about how climate scientists are compelled to lie for funding, they burst out laughing. It’s a conspiracy story as preposterous as the one where Richard Cheney wired the WTC towers with explosives. But try telling a Fox-Breitbart adherent how competition and pre-pub review really work, and they’ll tell you straight out that you’re lying and you’re a fool for letting the liberal media dupe you like that. The explanation of how scientists are motivated in the real world is facts and reason. Facts and reason can not usurp a tenet of a comprehensive mythology rooted in fear and resentment. I’m afraid the folks who are surprised at how grants work are the folks who are already receptive. The Fox-Breitbart adherents are not surprised at the idea that research grants work that way, they’ve already been taught that competition for correctness and novelty is suppressed in the climate related sciences by the liberal conspiracy. Anyone who tells them it’s still active is carrying water for the alarmist cabal.

  • Saskia van Manen

    I think you make an interesting point here, about needing to connect with audiences on a more emotional level. However, by subsequently providing facts to communicate, I think you make an even stronger point for leaving the communication of scientific findings to professional communicators, rather than to scientists themselves.

  • John Boyd

    Couldn’t agree more, but in my small experience, the difficulty is in actually engaging with people beyond point one.

  • Dan Zacharias

    While Dork Sahagian may disagree,

    1. Is the climate changing?
    Yes, there are many sources for data to indicate fluctuations in climate trends.

    2. Do people have anything to do with it?
    Yes, humans contribute to the change in climate. But contrary to claims otherwise, there is not a consensus that humans are the sole cause of climate change.

    3. Is climate change bad?
    No, while changes in climate will continue to impact human civilization as trends in climate change have since the beginning of human history. We, like our forebears will migrate and adapt. Modeling of precipitation patterns suggest increased atmospheric water vapor which in turn increases precipation contributing to erosion and other factors. These changes are projected to increase the carrying capacity of the Earth.

    4. Can we do anything about it?
    Yes, we can choose to increase our reliance on technology and thereby increase our power production which will inevitably increase greehouse gas emissions and warm the atmosphere. We can develop and test newer nuclear devices in the open air and sea. Furthermore, we can increase our commute times, eat more fiber and produce more methane. At it’s core, human behavior is where things need to change.

    5. Is it worth doing anything about?
    Yes, while the costs of adaption has by some accords been estimated to dwarf the cost of mitigating human contributions to warming trends, there are issues with the calculation of such cost projections. Humans will migrate to locations currently considered inhospitible due to the lack of resources primarily water. Post global climate change, annual precipitation is expected to increase, providing such resources to otherwise desolate geographic regions. The carrying capacity of the earth will increase, crops will not only thrive, but will be able to be grown year round.

    Sure there will be consequences such as endless mosquito seasons, more severe weather, and loss of property due to increased ocean levels. But, from my perspective, the pros outweigh the cons.

    We shall agree to disagree regarding the extent to which humans contribute to climate change. But to dismiss someone’s scientific based perspective because it’s contrary to an alleged consensus isn’t the way to convince someone. I’d venture to suggest that we would agree that further research upon the various disciplines of earth, environmental, meteorological, geophysics and other branches of science. Each person should study the research, ask questions, seek understanding, review the data, and formulate their own opinions.