The Heartland Institute Strikes Again. Part III.

September 6, 2017

The Heartland booklet spends considerable space arguing that there is no strong consensus among climate scientists that human activities are dominating ongoing climate change, while simultaneously admitting that most climate skeptics would rate human activity as a significant contributing factor in global warming.   In this post, we illustrate how the booklet seeks to undermine concern about future global warming impacts by the same techniques its authors use in other sections:  cherry-picked data, claims with no serious scientific backing, and misrepresentation of, or refusal to present, any of the much more abundant peer-reviewed research results that contradict their viewpoint.  We furthermore point out the dangers of following the booklet’s advice to avoid international consensus actions to mitigate human emissions of greenhouse gases.  We conclude with a summary of all the techniques from the Science Denier’s Toolbox used throughout the Heartland booklet.

5.  Scientific Consensus

 In keeping with its title, nearly one quarter of the Heartland booklet is devoted to fault-seeking not with the science supporting human contributions to global warming, but rather with numerous literature surveys that have claimed buy-in to these human contributions by a strong consensus among active climate researchers.  The authors of seven independent analyses of the degree of consensus have co-authored a publication (J. Cook, et al., 2016) that reaches the following conclusions:

1) Depending on exactly how you measure the expert consensus, it’s somewhere between 90% and 100% that agree humans are responsible for climate change, with most of our studies finding 97% consensus among publishing climate scientists.

 2) The greater the climate expertise among those surveyed, the higher the consensus on human-caused global warming.”

 In contrast, the Heartland booklet claims:

The articles and surveys most commonly cited as showing support for a “scientific consensus” in favor of the catastrophic man-made global warming hypothesis are without exception methodologically flawed and often deliberately misleading. … Many prominent experts and probably most working scientists disagree with the claims made by the United Nations’ Intergovernmental Panel on Climate Change (IPCC).

This disagreement bears on the question of just how settled the science is.  But, as pollsters learned long ago, the degree of consensus one finds on any question depends critically on (a) how the question is posed, and (b) possible biases (either pre-existing, self-selected or induced) in your polling sample.

For example, the papers reporting high degrees of consensus have generally focused on the level of agreement with the IPCC statement that “human influence has been the dominant cause of the observed warming since the mid-20th century.”  In contrast, the Heartland booklet refers to the Global Warming Petition Project, which has attracted over 31,000 co-signers for a petition containing the claim: “There is no convincing scientific evidence that human release of carbon dioxide, methane, or other greenhouse gases is causing or will, in the foreseeable future, cause catastrophic heating of the Earth’s atmosphere and disruption of the Earth’s climate.”  The former statement asks for a reasonably quantitative evaluation of evidence concerning past events, while the latter asks the reader to make a qualitative, subjective judgment about what might be “catastrophic” in the future.

There is also a striking difference in the polling samples for the two approaches.  Most of the surveys reporting strong consensus have focused either on peer-reviewed publications in climate science or on samples of scientists with expertise in the subject.  In contrast, the Petition Project mailed their petition to a selection (chosen by undisclosed means) of U.S. scientists in a wide variety of fields, along with a support letter from long-time libertarian science denier Frederick Seitz (who has argued in the past in favor of tobacco companies, against ozone depletion and acid rain).  In the mailing they also included a single “review” article that was published not in a recognized journal for climate research, but rather in the Journal of American Physicians and Surgeons, which specializes in publishing often flawed research that helps “to fight the government takeover of medicine.”

The global warming petition signers must have at least a B.S. degree in any one of a quite wide array of science disciplines, and need have no particular knowledge or expertise in climate science, beyond possibly reading the one-sided material that was enclosed with the petition. There is no reporting of how many of the more than 31,000 signers have done any climate research, nor of what percentage of scientists who received the petition actually signed.

It is clear from several surveys that support for the IPCC claim is correlated with the degree of knowledge and research activity in climate science. For example, Doran carried out a 2009 survey of earth scientists, asking for responses to the question: “Do you think human activity is a significant contributing factor in changing mean global temperatures?“. This question is posed again in a somewhat different way from the previously discussed surveys, substituting the word “significant” for “dominant”. But the results reveal the correlation shown in Fig. 23: the consensus grows from 76% to 97% as the responding scientists have greater familiarity with and activity in climate research. In contrast, only about 57% of the general public agreed with the question in 2008. Thus, it is clear that the degree of consensus depends strongly on who you sample.

Figure 23.  Percentage of respondents giving each of three possible answers to the Doran 2009 survey question “Do you think human activity is a significant contributing factor in changing mean global temperatures?” Earth scientist respondents are subdivided according to their degree of activity and knowledge of climate research, while the general public response (darkest blue) comes from a 2008 Gallup poll.

The Doran survey is one of the specific ones that the Heartland booklet tries to discredit, and the nature of its characterization is telling. The authors object to the fact that only earth scientists were included in this survey, and they focus on the small sample size associated with the lightest blue bar in Fig. 23. But they do not show the figure or comment at all on the findings for the other components of the sample. And in objecting to the formulation of the survey question, the Heartland booklet pulls the following bait and switch:

Most skeptics of man-made global warming would answer those two questions the same way as alarmists would. At issue is not whether the climate warmed since the Little Ice Age or whether there is a human impact on climate, but whether the warming is unusual in rate or magnitude; whether that part of it attributable to human causes is likely to be beneficial or harmful on net and by how much; and whether the benefits of reducing human carbon dioxide emissions – i.e., reducing the use of fossil fuels – would outweigh the costs, so as to justify public policies aimed at reducing those emissions. The survey is silent on these questions.”

In other words, in a document that devotes considerable space to misleading claims that global warming has stopped and is not likely due to human activity in any case, the Heartland authors here acknowledge explicitly that “human activity is a significant contributing factor in changing mean global temperatures.” This admission paints a quite different picture than their earlier, unsubstantiated claim that “probably most working scientists disagree with the claims made by the” IPCC. Rather, they shift the burden to issues of the consequences of climate change and to socio-political issues to be discussed in the following sections. And they gloss over what is really the central question regarding global warming: is the global temperature increase likely to become unusual in rate and magnitude if international fossil-fuel burning is allowed to continue the increase of greenhouse gas concentrations at the recent rate seen in Fig. 7 (Part I)?

In this context, their nit-picking objections to the methodology of other surveys showing strong consensus seem mostly for naught, since the consensus support is for the IPCC claim that more than 50% of recent global warming has an anthropogenic origin. They fail to cast doubt on the basic fact that the vast majority of climate research papers published in peer-reviewed scientific journals have presented data or model calculations that tend to support that IPCC conclusion. Instead, the Heartland authors attempt to cast aspersions on prolific researchers with libelous claims such as the following: “The extraordinary publication rate of alarmists should raise a red flag. It is unlikely these scientists actually participated in most of the experiments or research contained in articles bearing their names.” In other words, scientists who publish a lot of research are dishonest “alarmists,” while the integrity of the NIPCC members is manifested explicitly by their low publication rate!

One simple fact omitted from the Heartland booklet is the following: more than 2000 scientists have contributed to IPCC reports while the NIPCC website lists a total of 49 scientists who have contributed in any way (including as reviewers) to their reports. That ratio of involvement is quite consistent with roughly 97% of active climate researchers supporting the IPCC summary statements.

Furthermore, the Heartland booklet came out too soon to explain away a recent paper (Benestad, et al., 2016) whose authors attempted, without success, to replicate results of those 2% of peer-reviewed articles that have rejected the finding of anthropogenic global warming. Benestad, et al. conclude that those rejection studies exhibit systematic methodological flaws, “missing contextual information or ignoring information that does not fit the conclusions. …In many cases, shortcomings are due to insufficient model evaluation, leading to results that are not universally valid but rather are an artifact of a particular experimental setup. Other typical weaknesses include false dichotomies, inappropriate statistical methods, or basing conclusions on misconceived or incomplete physics.”

There is much ongoing scientific debate concerning the precise level of human contributions to climate change and details of the treatments of contributing factors in global climate models.  There is reason for skepticism regarding some claims of future impacts of climate change.  But the vast majority of scientists keeping abreast of the research agree there is significant reason for concern and mitigating actions.

6.   The Consequences of Climate Change

 If the Heartland authors agree that most climate skeptics would support the assertion that human activity is a significant contributing factor in changing mean global temperatures, then they must agree as well with the corollary:  changing human behavior is capable of affecting global warming.  The projections of global climate models have significant uncertainties, as we’ve seen, but they are in agreement that without a change in the rate of greenhouse gas emissions, the planet will warm on average by at least a few degrees during the present century.  Why, then, does the Heartland booklet argue against taking any international action to reduce greenhouse gas emissions?  This brings us to the crux of the Heartland argument.

In objecting to what they misidentify as the fifth “false postulate” of the IPCC (see Section 4a, Part I), the Heartland authors claim:

A warming of 2°C or more during the twenty-first century would probably not be harmful, on balance, because many areas of the world would benefit from or adjust to climate change.”

They state that the 2°C warming target suggested in IPCC assessments

is entirely arbitrary and … was set in response to concern that politicians would not initiate policy actions to reduce CO2 emissions unless they were given a specific (and low) quantitative temperature target to aim for.”

In addition, they imply that the IPCC failed to consider possible positive impacts of climate change:

The examples IPCC chooses to report invariably point to a negative impact on plant and animal life and human well-being.”

 The above claims in the Heartland booklet are again misleading.  Working Group II of the IPCC has, in fact, considered a wide range of possible impacts of increasing global temperatures and greenhouse gas concentrations, including positive as well as negative impacts, and also considering regional conditions.  They have considered these impacts as a function of global temperature rise, as summarized in Fig. 24.  They find that the negative impacts of a temperature increase by more than 2°C far outweigh the positive impacts.

Figure 24.  Illustrative examples of global impacts projected for climate changes (and sea level and atmospheric carbon dioxide where relevant) associated with different amounts of increase in global average surface temperature in the 21st century. The solid black lines link impacts, dotted arrows indicate impacts continuing with increasing temperature. Entries are placed so that the left-hand side of the text indicates the approximate onset of a given impact. Adaptation to climate change is not included in these estimations. The figure is taken from the WG II section of the IPCC 4th Assessment Report.

The onset of each impact considered in Fig. 24 is clearly an estimate; the impact assessment is not an exact science.  But among impacts anticipated to set in when global warming increases by more than 2°C are increasing risk of mass extinctions and increasing frequency of massive coastal flooding affecting many millions of people.  According to the WG II estimate, by the time global mean temperatures have risen by 3°C, about 30% of global coastal wetlands will be lost, leading to mass human migrations and enormous costs to manage those migrations.  That estimate is based on a projected mean sea level rise by 4.2 mm/year from 2000 to 2080.  In comparison, global sea levels have been observed to rise at about 3.2 mm/year already from 1990 to 2010 (see Fig. 21, Part II), so not much increase in rate of rise is projected as backing for this estimate of coastal jeopardy.

How does the Heartland booklet seek to discredit the WG II projections? They begin with a blanket strawman: “It is wrong to assume no changes would occur in the absence of the human presence. Climate, for example, will be different in 100 years regardless of what humans do or don’t do.” Well, nobody involved in this debate assumes that there are no climate drivers other than human activity.  And if humans perceive threatening climate trends, regardless of the driver, one would expect them to try to take action to change the trends.  Among the differences between the present climate trend and those natural global temperature cycles that occurred thousands or millions of years ago, is the fact that humans now have the technical sophistication to monitor, model and affect the climate.  Perhaps in this way they can help to avoid adding a new mass extinction event to the natural historical record in Fig. 12 (Part I).

With regard to dangers of sea level rise, the Heartland booklet says, “the best available data show sea-level rise is not accelerating.”  First of all, this is incorrect: global sea levels have risen since 1990 at a significantly higher rate than they did prior to 1990 (see Fig. 21, Part II).  Furthermore, as emphasized just above, it does not need to accelerate to pose a significant danger:  the rate of increase seen in Fig. 21 already threatens coastal areas within this century. The rise is attributed to both thermal expansion of the warming oceans and melting of land ice at high latitudes.  The rise is at the upper end of the past IPCC projections in Fig. 21 because those projections did not anticipate the rapid melting of ice sheets that has been observed. The Heartland booklet calls the data in Fig. 21 into question: “Satellite altimeter studies of sea-level change indicate rates of global rise since 1993 of more than 3 mm/year, but complexities of processing and the infancy of the method preclude viewing this result as secure.” They somehow fail to mention that the satellite data are completely consistent with the average trend indicated by independent tide gauge measurements (red line in Fig. 21).

Climate models consistent with the modest acceleration of sea level rise seen to date predict fairly rapid acceleration going forward at present rates of release of greenhouse gases to the atmosphere. This trend is shown in Fig. 25 for semi-empirical models calibrated against different data sets for global temperature and global sea level. All the curves in Fig. 25 have been generated under the moderate assumption that CO2 concentrations rise by the year 2100 to a value 2.3 times higher than the pre-industrial level, as they would if human greenhouse gas emissions peak in about 2040. Under this scenario, global temperatures would only increase by about 1.8ºC from the year 2000 to 2100. The most optimistic of the curves shown in Fig. 25 estimates that global sea levels would then rise by about 2.5 feet by the end of the century, with disastrous effects on coastal communities. The situation could be much worse in the absence of international actions to slow greenhouse gas emissions. And in this context, global warming is the “gift” that keeps on giving: so much heat will be stored in the oceans that sea levels will continue to rise for centuries, even if the warming ceases.

Figure 25.  Sea level hindcasts and projections (from Rahmstorf 2012) for semi-empirical models calibrated with different temperature and sea level data, under the assumption that climate forcing by the end of the century will be equivalent to CO2 concentrations a factor of 2.3 higher than pre-industrial levels. The colored bars at the right indicate the ranges within which the various model calibrations predict end-of-century sea levels to fall with 90% confidence.

With regard to effects of future climate change on water availability and food production, the Heartland booklet states that “Biodiversity is encouraged by warmer rather than colder temperatures, and higher temperatures and elevated CO2 greatly stimulate the growth of most plants.”  In support of this claim, they show Fig. 26, indicating increases in world grain production from 1961 to 2012.  They do not comment on how much these increases may have relied on increased land use, increased demand from a growing global population, and improved technology.  And they do not mention historical records that demonstrate food security being endangered by periods of extreme summer heat, which are known to reduce crop productivity, stress livestock, reduce soil moisture and increase water consumption.  For example, the 2003 heat wave in Europe caused 20 to 35% drops in the yields of key food crops.  Summer heat is projected to become much more extreme later in this century.

world grain production
Figure 26.  World grain production 1961-2012 as reported in the Heartland booklet.

The Heartland authors make the supportable statement that “any planetary change of 2°C magnitude in temperature would result in complex local and regional changes, some being of economic or environmental benefit and others being harmful.”  Indeed, such regional effects have been explicitly considered by WG II of the IPCC, and are reflected in Fig. 27, which shows projected changes in agricultural productivity by 2080 if global temperatures rise by 1 to 3°C.  Some regions, such as Northern Europe and North America, could benefit from a longer growing season, more precipitation, and less frost, depending on the crop. However, these regions can also expect more flooding, which can reduce yields. If local temperatures rise beyond 1 to 3°C, crop yields are likely to decline as rising heat affects water availability and plant development.

Figure 27.  Projected changes, by region, in agricultural productivity by the year 2080, from Cline (2007).

But food production is projected to decline in tropical regions as rising temperatures decrease crop yields. Drought-prone areas of Africa are particularly vulnerable to food shortages due to a reduction in the land area suitable for agriculture. Agricultural losses could be severe in the Sahel, East Africa, and southern Africa. A study of some North African countries suggests that some rain-fed crop yields could decline as much as 50 percent in extreme years by 2020. Degradation of coral reefs and mangroves, as well as rising lake temperatures and overfishing, could decrease fish supplies in Africa.

The Heartland booklet doubts that there will be more extreme weather events (floods, storms, droughts, etc.) as the planet warms:  “Basic meteorological science suggests a warmer world would experience fewer storms and weather extremes, as indeed has been the case in recent years. … The commonly held perception that twentieth century warming was accompanied by an increase in extreme weather events is a misconception fostered by excessive media attention and has no basis in facts.” The “basic meteorological science” to which they refer appears to be backed up only by the following statement: “Air temperature variability decreases as mean air temperature rises, on all time scales.”  The booklet simply ignores such meteorological facts as the following: warmer oceans serve as breeding grounds for more severe hurricanes and cyclones; warmer air holds more water vapor, leading to more severe rainfall during storms; storm surges superimposed on rising sea levels lead to more severe flooding in coastal regions.

The occurrence of recent “once-per-century” or “once-per-millennium” storms, such as Hurricanes Katrina, Sandy and, most recently, Harvey – and the enormous damage they have wrought, respectively, in New Orleans, New York and New Jersey, and Houston – should be taken as early warning signs ignored at our own considerable risk. As for the Heartland booklet’s claim of no basis in facts, this ignores evidence such as Fig. 28, showing the number of annual natural disasters worldwide through the period from 1980 to 2017, as compiled by reinsurance company Munich RE. While the frequency of geophysical events, such as earthquakes and volcanoes, has been fairly steady over this period, extreme meteorological, hydrological and climatological events have tripled in frequency as the planet has warmed and sea levels have risen. As the Heartland booklet points out elsewhere, correlation does not prove causation, but it sure gives food for thought.

As evidence to support their claim that human activity is not causing extreme heat waves, the Heartland authors include Fig. 29, which shows that the average number of daily high temperatures recorded in the U.S. above 100°F does not seem to have grown in the late 20th century.  The plot includes data only for the U.S., while the global trend is quite different.  And furthermore, Fig. 29 actually makes the point that human activity can cause extreme weather.  Days above 100°F in the U.S. have traditionally been dominated by the American southwest, which experienced a Dust Bowl accounting for the peak years in the mid-1930’s in Fig. 29.  Human impact on the Dust Bowl has been summarized as follows: “poor land use practices and many years of intense drought contributed to these heat waves by depleting soil moisture and reducing the moderating effects of evaporation.

Munich Re statistics on worldwide natural disasters 1980-2017
Figure 28. The annual number of worldwide natural disasters recorded from 1980 through 2017. While the frequency of geophysical events (reddish brown) has remained roughly constant throughout that period, the frequency of meteorological (green), hydrological (blue) and climatological (gold) events has nearly tripled, as global temperatures and sea level have risen. Statistics from Munich RE reinsurance group’s NatCatService.
hundred degree days
Figure 29.  The average number of daily high temperatures above 100 degrees Fahrenheit recorded across 982 U.S. stations vs. year from 1895 to 2014, taken from the Heartland booklet. The peak in the mid-1930’s is associated with the “Dust Bowl” in the American southwest.

Globally, the number of heat waves recorded each year has increased and the heat waves have grown longer since 1950.  One way to see this effect, just within the U.S., is shown in Fig. 30.  This figure, from Meehl, et al. (2009), plots the annual total number of daily temperature records, both high and low, recorded in U.S. locales as a function of year.  It includes recorded data from 1950, when good record-keeping was available everywhere in the country, as well as projected data out to 2100.

US temp highs and lows vs year
Figure 30.  The annual number of record high (red) and record low (blue) temperatures recorded across the U.S. between 1950 and 2008, and projected out to 2100 within a global climate model, from Meehl, et al. (2009). Both high and low records decrease in frequency since the beginning of good record-keeping, but record highs are currently being recorded at twice the rate of record lows.

Both high and low records in Fig. 30 decrease rapidly in frequency from the beginning of good record-keeping, simply because it’s easiest to set records when few were previously recorded. However, the frequency of record lows has decreased much faster than that of record highs, so that presently it is roughly twice as likely to experience record high temperatures as record lows. (Note that the vertical scale in Fig. 30 is logarithmic.) Projected out to the end of this century at anticipated rates of greenhouse gas emissions, record highs will become about 20 times as probable as record lows. The black curve in Fig. 30 shows the trend that would be expected for both highs and lows if the climate were not changing. The frequency of record lows deviates further from the black curve than that of record highs because nights are warming faster than days (see Fig. 5, Part I).

In summary, the Heartland booklet tries to undermine concern about future global warming impacts by the same techniques they use in other sections.  They present cherry-picked data, make claims with no serious scientific backing, and misrepresent or refuse to present any of the much more abundant peer-reviewed research results that contradict their viewpoint.

7.  The Danger of the Null Hypothesis

 In the end, the Heartland booklet recommends that the most prudent path for public policy is to adopt

the null hypothesis that currently observed changes in global climate indices and the physical environment are the result of natural variability. … NIPCC’s conclusion, drawn from its extensive review of the scientific evidence, is that any human global climate impact is within the background variability of the natural climate system and is not dangerous.  In the face of such facts, the most prudent climate policy is to prepare for and adapt to extreme climate events and changes regardless of their origin.”

 This advice sounds quite similar to that from Noah’s “advisors” that the younger S. Fred Singer warned against:

’Don’t worry about the rising waters, Noah; our advanced technology will surely discover a substitute for breathing.’ If it was wisdom that enabled Noah to believe in the ‘never-yet-happened,’ we could use some of that wisdom now.

The NIPCC advice is certainly in marked contrast to the “precautionary principle” adopted by the IPCC and the vast majority of international governments.  Those governments see strong scientific evidence (some of it reviewed in this blog post) that fossil fuel burning by humans is the dominant driver of ongoing global warming, and that government actions can help to prevent or at least mitigate the possibly disastrous consequences.  The vast majority of governments seem to be in agreement that the costs of preventive action now, while substantial, are still far lower than the eventual costs that would be incurred by waiting to adapt to the consequences of global warming when they occur later in this century.

What is the danger of adopting the “null hypothesis”?  There is still substantial uncertainty in projections of global climate models and remaining disagreements over the precise magnitude of the greenhouse gas contributions to warming, even if the Heartland booklet makes a very weak case for the real disagreements by its dishonest representation of one side of the argument.  So why not wait until there is more data and further improvement of the climate models, before deciding on public policy?

The danger of delay is that the costs of preventive action rise rapidly, while its efficacy sinks, as time goes on.  This conundrum is described schematically in the video below from the website  A healthy public debate on climate policy – which we are certainly not experiencing now in the U.S. – relies on an honest presentation of the scientific background and its uncertainties, along with fair-minded estimates of the costs of action vs. delayed action vs. inaction.

Furthermore, preventive actions include a number of conservation and renewable energy development steps that will, in fact, lead to long-term savings and job creation, as well as reductions in greenhouse gas emissions. Why should anyone, other than representatives or investors of competing industries, object to those actions? And yet, the Heartland Institute has worked to develop legislation opposing government support for renewable energy development. The cost savings from such actions can help to counterbalance the substantial costs from other actions taken to reduce greenhouse gas emissions, as summarized in the next video, also from

Finally, why should preventive actions to mitigate global warming be addressed internationally?  The Heartland booklet recommends that: “Individual nations should take charge of setting their own climate policies based upon the hazards that apply to their particular geography, geology, weather, and culture.” This recommendation is reflective of the libertarian political outlook of the authors and of the Heartland Institute, and of their distaste for preventive government action.  But it ignores the fact that greenhouse gas emissions from any country affect the climate globally.  In addition, the hazards that can result involve global issues, not just ones dependent on local conditions.  For example, the mass migrations away from coastal areas that would result if global sea levels rise by more than two feet will create international problems, even for land-locked countries that have to play a part in accommodating immigrants.  Fostering an outlook that allows every country to decide for itself how to proceed guarantees that there will be no effective precautionary actions to mitigate global impacts.

 8. Summary

The Heartland booklet is a classic case study in the techniques we have exposed elsewhere on this site as the Science Deniers’ Toolbox.  It uses cherry-picked results, most often not from peer-reviewed research papers, to support its misinformation campaign.  It repeats the misinformation often, while ignoring evidence-based refutations of its claims, refutations which the authors have certainly seen, but which they reject because they undermine their predetermined conclusions.  That rejection allows them to misidentify well-founded conclusions of climate scientists as unsupportable “postulates.” Rejection of the evidence is a signature of science denial, as opposed to scientific skepticism.  Of the 30 figures included in this post, the Heartland booklet presents only 6 (Figs. 2, 13, 16, 19, 26 and 29), omitting the much more abundant results that refute their claims.  (The Heartland booklet contains only 8 graphs in all, six of which have been presented here.)  Their goal is not to disprove the science behind global warming, but rather only to delay policy decisions until it becomes too late to act.

The booklet magnifies quibbles about details among active climate researchers to claim fundamental disagreements about basic conclusions.  It complains about conspiracies, self-interest, politicization and even dishonesty among the many research scientists who contribute to IPCC reports, while hiding the authors’ own funding sources and political agenda.  It questions the usefulness of models that don’t yet include all conceivable effects, and misrepresents data to claim misleading model “failures.”  It demands definitive evidence that serious predicted ill effects are already seen, by which time it’s too late to prevent them.  Rather than arguing to improve climate models and benchmark them against more extensive, newly acquired data, its publisher lobbies for reduced research funding for these activities.

The booklet changes its story as needed to support persistent conclusions.  This leads to a number of significant internal inconsistencies within the booklet.  It seeks to discredit global climate models because they do not contain a “perfect” representation of climate behavior, but then relies on analyses based on much less sophisticated models to argue for low sensitivity of global temperatures to the Earth energy imbalance caused by greenhouse gas increases.  It argues that CO2 increases played no role in warming associated with the emergence from past ice ages, without acknowledging that, if this were true, it would require the sensitivity of global temperatures to a given Earth energy imbalance to be even much greater than the estimates in IPCC climate models.

The booklet discredits a survey showing strong scientific consensus for human-induced global warming, by arguing that “most skeptics of global man-made warming would” agree with the survey question, “Do you think human activity is a significant contributing factor in changing mean global temperatures?”  But in concluding the same booklet, the authors claim: “The key questions to be answered, however, are whether the human global signal is large enough to be measured and if it is, does it represent, or is it likely to become, a dangerous change outside the range of natural variability?” If the human global signal is not necessarily large enough to be measured, why would most climate skeptics rate it as a significant contributing factor?  And contrary to the implication in the booklet’s conclusion, climate changes do not have to fall outside the range of natural variability to be dangerous:  past natural events have led to a sequence of mass extinction events among living species.

Finally, and most importantly, among the techniques from the Science Deniers’ Toolbox, the Heartland booklet targets education so that the authors’ science denial can attain longevity.  They promote a false equivalence of all viewpoints, so that all should be taught on equal footing in science education.  In our opinion, the best use of Why Scientists Disagree About Global Warming in an educational context is to teach students how to recognize the standard techniques of science denial.  This could be done, for example, via student debates about climate change based on presentations in this post, or in some of the excellent websites included among our sources below.

Some suggestions for leading student discussions of material in Part III of this post:

  • Discuss with students the difference between consensus and unanimity about scientific results. Ask them why they think different polling techniques sometimes reach apparently inconsistent conclusions.
  • Ask the students to try to estimate how many people globally might be forced to migrate if sea levels rose by more than two feet. Ask them to estimate how long such a rise would take if levels continue to rise at the presently observed rate of 3.2 millimeters per year.
  • Discuss with students some of the climate change impacts considered by the IPCC in Fig. 24.
  • Ask students to discuss the significance of Fig. 28, showing the frequency of climate-related disasters.
  • In the light of figures such as Fig. 27, showing projected regional changes in agricultural productivity, have students debate whether each country should be allowed to choose its own climate policy or international consensus is needed.
  • Ask the students what they may have learned from the discussions of climate science about how to judge scientific evidence and how to recognize flawed or misleading arguments.

9. Sources

 C.D. Idso, R.M. Carter and S.F. Singer, Why Scientists Disagree About Global Warming: the NIPCC Report on Scientific Consensus (

The Heartland Institute website (

The NIPCC website (

The IPCC website (

The Center for the Study of Carbon Dioxide and Global Change (

Wikipedia, The Heartland Institute (

Wikipedia, The United Nations Framework Convention on Climate Change (

N. Oreskes and E. Conway, Merchants of Doubt (Bloomsbury Press, New York, 2010) (

Skeptical Science website (

Climate Communication website (

The Consensus Project (

The Scientific Guide to Global Warming Skepticism (

Making Sense of Climate Science Denial (

M.E. Mann, S. Rahmstorf, B.A. Steinman, M. Tingley and S.K. Miller, The Likelihood of Recent Record Warmth, Scientific Reports 6, article #19831 (2016) (

J. Cook, et al., Consensus on Consensus: A Synthesis of Consensus Estimates on Human-Caused Global Warming, Environmental Research Letters 11, 048002 (2016) (

Global Warming Petition Project (

G.A. Meehl, C. Tebaldi, G. Walton, D. Easterling and L. McDaniel, The Relative Increase of Record High Maximum Temperatures Compared to Record Low Minimum Temperatures in the U.S., Geophysical Research Letters 36, L23701 (2009) (  


IPCC 4th Assessment Report (2007) (

J.D. Shakun, et al., Global Warming Preceded by Increasing Carbon Dioxide Concentrations During the Last Deglaciation, Nature 484, 49 (2012) (

D. Nuccitelli, R. Way, R. Painting, J. Church and J. Cook, Comment on Ocean Heat Content and Earth’s Radiation Imbalance. II: Relation to Climate Shifts (

T.R. Karl, S.J. Hassol, C.D. Miller and W.L. Murray (Eds.), Temperature Trends in the Lower Atmosphere: Steps for Understanding and Reconciling Differences. A report by the Climate Change Science Program and Subcommittee on Global Change Research ( report/default.htm)

C. Monckton, W.W-H. Soon, D.R. Legates and W.M. Briggs, Keeping It Simple: The Value of an Irreducibly Simple Climate Model, Science Bulletin 60, 1378 (2015) (

P.T. Doran and M.K. Zimmerman, Examining the Scientific Consensus on Climate Change, EOS 90, No. 3, 22 (2009) (

R.E. Benestad, D. Nuccitelli, S. Lewandowsky, K. Hayhoe, H.O. Hygen, R. van Dorland and J. Cook, Learning from Mistakes in Climate Research, Theoretical and Applied Climatology 126, 699 (2016). (

S. Rahmstorf, M. Perrette and M. Vermeer, Testing the Robustness of Semi-Empirical Sea Level Projections, Climate Dynamics 39, 861 (2012) (

W.R. Cline (2007), Global Warming and Agriculture: Impact Estimates by Country (!prettyPhoto/0/)