September 5, 2017
The Heartland Institute aims to indoctrinate a generation of young students in the elements of denialism concerning any scientific research used to support government regulation threatening their extreme free-market political philosophy. In their recently distributed booklet “Why Scientists Disagree About Global Warming,” they apply most elements of the standard Science Denier’s Toolbox to cast doubt about the existence and causes of climate change. They make murky and unsubstantiated claims of an implausible conspiracy among the thousands of scientists and 195 countries that have contributed to the Intergovernmental Panel on Climate Change. In this blog post we examine the Institute’s deeply flawed track record and begin to expose the deliberately blindered and misleading presentation of published climate research in their booklet.
1. Heartland’s Long Game
In March 2017 the Heartland Institute launched an unsolicited mailing of their booklet Why Scientists Disagree About Global Warming, along with a companion DVD to all 200,000 K—12 science teachers in the U.S. They included a cover letter with a link to an online course planning guide. This action represents follow-through on the Institute’s plans – first revealed in an unauthorized 2012 public release of many of their internal documents – to develop curriculum materials to promote climate skepticism (actually, denial, as we will expose in this blog post) in U.S. schools.
Heartland’s plans for re-education most likely extend well beyond climate science over the long term. As far back as 1994, Heartland publicly advocated for privatization of public schools and school vouchers. The Institute has established a Center for Transforming Education. Their long game appears to focus on indoctrination with “alternative facts” that support the Institute’s clear political agenda, described in the following section.
This blog post centers on the recently mailed booklet. We seek to expose the many well-worn techniques from the Science Denier’s Toolbox that the booklet employs to confuse teachers and students about science, and the deep internal inconsistencies in its arguments. Sources we have used to gather information for this post will be listed at the end of Part III of the post.
As the title of their booklet makes clear, Heartland’s intention is primarily to drive home the idea that there is so much disagreement about climate science that it makes no sense to take any action to reduce greenhouse gas emissions. But like many of the political operators who proclaim publicly that “the science is unsettled,” they work behind the scenes to reduce funding for further climate research and for development of renewable energy alternatives. In reality, then, they appear to have little interest in actually settling the science or in preparing for the eventuality that the present strong scientific consensus turns out to be correct. They are interested only in delaying any government regulations until it is too late for them to have effect.
2. What Is the Heartland Institute and What Do They Advocate?
It always pays to explore the track record of groups who propose to instruct you, so you know where they’re coming from. According to its own website,
“The Heartland Institute is one of the world’s leading free-market think tanks. It is a national non-profit research and education organization based in Arlington Heights, Illinois. Its mission is to discover, develop and promote free-market solutions to social and economic problems. We are an ‘action tank’ as well as a ‘think tank,’ and we measure our success by the impact we have in the real world. The Heartland Institute plays an essential role in the national (and increasingly in the international) movement for limited government and personal liberty. We are the pipeline between the freedom movement’s leading writers and thinkers and the nation’s 8,400 national and state elected officials.”
This mission statement clearly establishes Heartland as an organization with primarily political, specifically libertarian, ambitions and leanings. It was founded in 1984 by David H. Padden, who had previously served as Director of the Cato Institute, a libertarian think tank in Washington, D.C. formerly known as the Charles Koch Foundation. Along with climate science denial, Heartland has advocated for smokers’ rights, privatization of public resources including public schools, school vouchers, and lower taxes. They have advocated against subsidies and tax credits for individual businesses, against threats posed by secondhand smoke, acid rain and ozone depletion, against the Endangered Species Act, and against an expanded federal role in health care. In the 1990’s they actively collaborated with the tobacco industry to question links of smoking and secondhand smoke to cancer and other lung diseases, as typified by the essay “Joe Camel is Innocent,” written by the Heartland President and CEO Joseph Bast. They have written model legislation to repeal mandates supporting renewable energy sources, such as solar and wind power, legislation adopted in 2012 by the American Legislative Exchange Council (ALEC) and shared with state governments throughout the U.S.
Although the Heartland Institute no longer discloses its funding sources, it has received in the past substantial donations from politically conservative (e.g., Castle Rock, Sarah Scaife, John M. Olin, Lynde and Harry Bradley) foundations and from tobacco, pharmaceutical and oil companies. Heartland currently claims that no single corporate entity donates more than 5% of its operating budget, but single anonymous donors have contributed up to 20% of Heartland’s overall budget.
We have no issue with the strong libertarian advocacy and funding of the Heartland Institute. But it does call into question the concluding section of Why Scientists Disagree About Global Warming, where they appear to identify themselves as among “independent, nongovernment organizations and scientists who are free of financial and political conflicts of interest.”
Heartland’s tactics also identify them as a political, rather than independent scientific, organization. For example, in 2012 they launched an advertising campaign in the Chicago area featuring a billboard with a photo of Unabomber Ted Kaczynski over the caption “I still believe in global warming. Do you?” They planned to continue the campaign with other billboards replacing Kaczynski’s photo with those of Charles Manson, Fidel Castro and Osama Bin Laden over the same caption. They justified these billboards with the statement, “The most prominent advocates of global warming aren’t scientists. They are murderers, tyrants and madmen.” When their campaign went over like a lead balloon, their President Joseph Bast issued the following statement of clarification: “We know that our billboard angered and disappointed many of Heartland’s friends and supporters, but we hope they understand what we were trying to do with this experiment. We do not apologize for running the ad, and we will continue to experiment with ways to communicate the ‘realist’ message on the climate.”
When Pope Francis issued the 2015 encyclical Laudato Si, laying out the Catholic Church’s moral case for addressing climate change, Gene Koprowski, the marketing director for the Heartland Institute, responded that “pagan forms are returning to the Church this day.” These incidents do not reflect an interest in dispassionate scientific debate. The recently mailed booklet, however, represents an attempt to take a more scientific-sounding approach. Local high school science teachers have told us that they find Why Scientists Disagree About Global Warming to be effectively produced. So we judge it important to analyze and deconstruct this approach for science teachers and students who may not recognize its techniques.
3. The NIPCC: Projecting Politicization
Why Scientists Disagree About Global Warming is officially a report of the Nongovernmental International Panel on Climate Change, NIPCC, published by the Heartland Institute. An appendix to the document provides a self-description of the NIPCC:
“The Nongovernmental International Panel on Climate Change (NIPCC) is what its name suggests: an international panel of nongovernment scientists and scholars who have come together to understand the causes and consequences of climate change. Because we are not predisposed to believe climate change is caused by human greenhouse gas emissions, we are able to look at evidence the Intergovernmental Panel on Climate Change (IPCC) ignores. Because we do not work for any governments, we are not biased toward the assumption that greater government activity is necessary.
NIPCC traces its roots to a meeting in Milan in 2003 organized by the Science and Environmental Policy Project (SEPP), a nonprofit research and education organization based in Arlington, Virginia. SEPP, in turn, was founded in 1990 by Dr. S. Fred Singer, an atmospheric physicist, and incorporated in 1992 following Dr. Singer’s retirement from the University of Virginia. NIPCC is currently a joint project of SEPP, The Heartland Institute, and the Center for the Study of Carbon Dioxide and Global Change.”
There is a lot to deconstruct in this description. The self-organized NIPCC has clearly chosen both its name and its mission to contrast views and claims of “purity” with the IPCC established by the United Nations in 1988 “to provide the world with a clear scientific view of the current state of knowledge in climate change and its potential environmental and socio-economic impacts.” The IPCC engages thousands of scientists from all over the world, on a purely voluntary basis, to provide regular scholarly input in support of the 1992 United Nations Framework Convention on Climate Change (UNFCCC), which has been ratified by 197 countries, including the U.S. The UNFCCC objective is to “stabilize greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system.”
The UNFCCC does not predetermine what level of contribution to climate change is attributed to human activities nor what level would constitute “dangerous interference.” The IPCC is organized into three working groups (WGs), with the one most relevant to the Heartland Institute booklet being WG I. WG I “aims at assessing the physical scientific basis of the climate system and climate change. Its main topics include: changes in greenhouse gases and aerosols in the atmosphere; observed changes in air, land and ocean temperatures, rainfall, glaciers and ice sheets, oceans and sea level; historical and paleoclimatic perspective on climate change; biogeochemistry, carbon cycle, gases and aerosols; satellite data and other data; climate models; climate projections, causes and attribution of climate change.”
Despite the IPCC encompassing contributions from a majority of the world’s leading experts on the science of climate change, the Heartland document characterizes it this way: “The IPCC, created to find and disseminate research finding a human impact on global climate, is not a credible source. It is agenda-driven, a political rather than scientific body, and some allege it is corrupt. Finally, climate scientists, like all humans, can be biased. Origins of bias include careerism, grant-seeking, political views, and confirmation bias.” In other words, the basic view of the NIPCC is that thousands of scientists and the 195 countries now contributing to the IPCC have a common interest in conspiring to pull off a major scientific hoax (an unspecified “some allege it is corrupt”), rather than in working to avoid an environmentally fraught future for the planet. In contrast, the 49 contributors to the Heartland document are presented as scientists pure of heart and without political bias.
Let’s examine that underlying premise. One of the three lead authors of the Heartland booklet is S. Fred Singer, who has made other appearances in blogs on this site (e.g., see The Ozone Layer Controversy, Part II). He has previously played major roles in fighting against the scientific bases for tobacco’s dangers to health, for CFCs as a driver of ozone layer depletion and for the role of polluting emissions in causing acid rain. In each of those earlier cases, subsequent developments have proved the doubts Singer cast upon the science to be greatly overblown, as were his exorbitant estimates of the costs of mitigating preventive action. What has been consistent is his economic and political outlook on these issues. In a 1979 report entitled Cost-Benefit Analysis as an Aid to Environmental Decision-Making, he stated: “The public policy conclusion from our analysis is that where a choice exists, one should always choose a lower national cost, i.e., a conservative approach to air pollution control…” Of course, cost-benefit analyses are easier than scientific data to tilt with political leanings, by systematically overestimating the costs of action and underestimating those of inaction.
As noted in Naomi Oreskes’ and Erik Conway’s book Merchants of Doubt, Singer’s libertarian political leanings overtook his scientific judgment some time during the 1970s. Since the middle of that decade, Singer’s persistent viewpoint in all of these cases has been that the science is too uncertain, and the negative implications too unproven, to be used as a basis for political action. Besides, if the dire predictions turn out to be correct, then humans will develop the technology to combat them when the negative implications become reality. These views directly contradict those of the younger S. Fred Singer, who in a 1970 article Global Effects of Environmental Pollution had stated: “If we ignore the present warning signs and wait for an ecological disaster to strike, it will probably be too late.” In that same article, Singer imagined Noah being advised by skeptics: “’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.”
A second lead author of the Heartland booklet is Craig D. Idso, Chairman of the Center for the Study of Carbon Dioxide and Global Change. That Arizona-based Center is largely a family affair, with Idso’s father serving as President and his brother as Vice-President, completing the set of key personnel identified on their website. The Idsos promote the view that rising carbon dioxide levels will have primarily beneficial environmental impacts. The third lead author, now deceased, is Robert M. Carter, an English paleontologist who served on the research committee of the Institute of Public Affairs, an Australian free-market think tank that promotes climate change denial.
Leaked documents from the Heartland Institute in 2012 showed that the Institute provides “funding for high-profile individuals who regularly and publicly counter the alarmist AGW [anthropogenic global warming] message,” including substantial monthly support for the three lead authors of Why Scientists Disagree About Global Warming.
Their political leanings, family viewpoints and libertarian donor funding do not necessarily predetermine the scientific outlook of the NIPCC members, any more than research funding provided by many different governments makes the IPCC contributors suspect of corruption. But they do suggest an informed reading of their carefully worded self-description: “we are not predisposed to believe climate change is caused by human greenhouse gas emissions” should properly be read as “we are predisposed to believe climate change is not caused by human greenhouse gas emissions”; “we are not biased toward the assumption that greater government activity is necessary” should be read as “we are biased toward the assumption that greater government regulation is never necessary.” It seems like political projection (preemptively accusing your opponents of shortcomings that would otherwise be associated with you) for the NIPCC to accuse the IPCC of being “a political rather than scientific body” and to imply that IPCC findings are predetermined by human and confirmation bias.
The question that needs to be judged is whether the NIPCC’s scientific claims pass the test of skepticism, rather than denial. That is the subject of the next section.
4. Misleading Scientific Arguments
The Heartland booklet mixes philosophical, sociological and economic arguments in with some deliberate misrepresentations of the science supporting climate change concerns. The central themes of their arguments can be boiled down to the following:
i. The IPCC “assumed” its conclusions – findings are misidentified in the Heartland booklet as “postulates” and essentially all of the research backing up those findings is ignored, as we will document in Section 4a of this post.
ii. IPCC projections are based on global climate models that are not perfect and that employ adjustable parameters – the booklet ignores the fact that all of science progresses via the development of imperfect models with adjustable parameters that are gradually improved, and occasionally subsumed in fundamental theories, by more sophisticated treatment of contributing effects and by ongoing comparison to steadily improving experimental data. We will expose in Section 4b of this post (in Part II) the cherry-picking and misrepresentation techniques the Heartland booklet employs in its attempt to discredit those global climate models.
iii. Atmospheric carbon dioxide levels may be rising, but the IPCC models greatly overestimate the sensitivity of global temperature to CO2 concentrations – the booklet ignores the preponderance of evidence supporting the sensitivity estimates and their uncertainty, while relying on even more simple-minded model results to argue for very much lower sensitivity. We will discuss the deep inconsistencies in Heartland’s arguments in Section 4c (Part II).
iv. CO2 levels have historically resulted from, rather than caused, global temperature increases – they have in fact done both, while the booklet ignores the fact that the primary climate drivers upon initial emergence from an ice age are quite different from those currently forcing Earth’s climate. The historical record is discussed in Section 4a.
v. Current and conceivable future climate changes are within ranges of those that occurred in the past due to purely natural causes, and are thus not causes for concern – the booklet conveniently ignores the fact that massive human populations were not around to deal with those earlier climate changes, some of which led to mass extinctions of living species. The mass extinctions are discussed in Section 4a, while more general projected consequences of global warming, whether it be natural or human-induced in origin, are discussed in Section 6 (Part III).
vi. There is no scientific consensus on the causes or magnitude of climate change, so the most sensible plan is to do nothing – the booklet goes to great lengths to deny the level of scientific consensus, and then argues philosophically for the virtue of a “null hypothesis”, as opposed to a “precautionary principle.” We discuss the scientific consensus in Section 5 and the danger of the null hypothesis in Section 7, both in Part III of this post.
vii. If something is to be done, it should not be a global issue, but mitigations and responses should be left to each individual country to determine for itself – the booklet treats potential consequences of climate change as local problems (or benefits) that need not bother us, ignoring lessons that should have been learned from the ozone layer controversy or such current problems as mass emigration from Syria. We refute Heartland’s dismissal of harmful global consequences of climate change in Section 6 and the need for a global response in Section 7 (both in Part III).
In the concluding Section 8 of this post, we will summarize all the techniques from the Science Denier’s Toolbox that the Heartland booklet employs to obfuscate the actual scientific facts and consensus.
In this subsection we deal with the historical data and some of the underlying science that backs up claims of human impacts on climate change. We illustrate how the Heartland booklet simply ignores the existence of most of these data and employs severe cherry-picking to misrepresent the data it does display. By this deliberate misrepresentation, the authors attempt to treat clear research findings as mere unproven assumptions.
The Heartland booklet treats the following (sometimes intentionally misrepresented) points as IPCC postulates, implying that there is and can be no independent evidence supporting them. Thus, they claim they are merely unjustified assumptions made by climate “alarmists” to support their predetermined, politically motivated conclusions.
- The warming of the twentieth century cannot be explained by natural variability.
- The late twentieth century warm peak was of greater magnitude than previous natural peaks.
- Increases in atmospheric CO2 precede, and then force, parallel increases in temperature.
- Solar forcings are too small to explain twentieth century warming.
- A future warming of 2°C or more would be net harmful to the biosphere and human well-being.
No climate scientists deny the existence of natural climate cycles. They are indicated clearly in Fig. 1 (not shown in the Heartland booklet), which uses data gleaned from Antarctic ice core samples to illustrate the climate cycles the Earth has gone through over the past 800,000 years.
The most striking conclusion from the data in Fig. 1 is that temperature is very strongly correlated with concentrations of CO2 and methane (CH4). All show cyclical behavior, with the most prominent repetition period on the order of 100,000 years. The physical mechanism for this periodic occurrence of and emergence from ice ages is well understood: it arises from periodic variations in Earth’s orbit around the Sun and in the tilt angle of Earth’s axis with respect to the plane of its orbit. Earth emerged from its last Ice Age about 20,000 years ago, and in the presence of purely natural drivers would presently be cooling toward the start of the next glacial period, anticipated to come several thousand years from now.
The next most striking conclusion from Fig. 1 is that the very recent rises in CO2 and CH4 levels, seen at the extreme right edge of the graph, are much larger and have occurred much more rapidly than has been seen over the past million or so years on Earth. Neither the IPCC nor other responsible climate scientists have claimed, as the NIPCC suggests, that “the late twentieth century warm peak was of greater magnitude than previous natural peaks.” The deglaciation periods following naturally occurring ice ages have indeed featured large global temperature changes, though there were not huge human populations subjected to those effects. But, as will be discussed shortly, increasing greenhouse gases played major roles in driving much of those deglaciation temperature increases. That makes the ongoing rapid increase in greenhouse gas concentrations a cause for serious concern.
There are a number of natural climate drivers besides Earth orbit variations. Over hundreds of millions of years, the power reaching Earth’s atmosphere from the Sun has changed by several percent. On a much shorter time scale, there is a well-known 11-year cycle during which solar activity oscillates by about one tenth of one percent. There are also inferred solar activity variations of similar magnitude that occur over century time scales. There are year-to-year fluctuations in climate that result from volcanic eruptions or from ocean circulation phenomena that cause, for example, el niño and la niña. And of course, there are seasonal variations in climate.
In order to support their claim that such natural climate changes occur all the time, the NIPCC shows in the Heartland booklet the temperature record of Fig. 2, although without our added annotations. If they were interested in an honest scientific debate, they would not have included an arbitrary cutoff at the year 1900 for this graph!
There is an ongoing scientific debate concerning all the natural factors that may have contributed to the Medieval Warm Period (MWP) and Little Ice Age (LIA) periods highlighted in Fig. 2. But the primary driver for those periods appears to have been slight variations in solar activity (upward during the MWP and downward during the LIA), as inferred from slight changes in the measured concentrations of the radioactive isotope carbon-14 in tree rings. Carbon-14 is produced in the atmosphere with the aid of solar energy.
Compare Fig. 2 to Fig. 3, which shows the actual peer-reviewed temperature measurements or reconstructions from various sources, spanning the same two millennia, but now without the artificial cutoff at 1900. Clearly, the Heartland booklet has chosen to hide the fact that the 20th century rise in global temperatures is considerably larger in both magnitude and rapidity than the earlier variations considered in Fig. 2. The change in these characteristics already suggests that different climate drivers may be in play currently.
There are many lines of evidence that have convinced climate scientists that solar forcings cannot explain the late 20th century warming. This is a finding, not – as the Heartland booklet claims by simply ignoring all of the evidence we’re about to present — a postulate. First of all, as shown in Fig. 4, there is no correlation of the recent warming beyond 1960 with independent satellite measurements of solar irradiance of the upper atmosphere. The Earth has warmed while solar activity has been roughly constant, or even decreased more recently.
Furthermore, the characteristics of the recent temperature rise shown in Fig. 5 argue against a dominant role for solar activity. Nights have warmed even more rapidly than days, while one would expect the opposite to be true if solar activity were the primary cause of the warming. The lower atmosphere (troposphere) has warmed, while the upper atmosphere (stratosphere) has cooled, whereas increased solar activity would have brought in more energy from above and warmed both.
However, just the pattern observed in the right-hand frame of Fig. 5 is expected when the primary driver of the temperature change is increased greenhouse gas concentrations in the atmosphere. This point requires a bit of elaboration. Energy incoming to the atmosphere from the sun is primarily in the visible and ultraviolet regions of the electromagnetic spectrum. The Earth maintains an equilibrium temperature by radiating back out through the atmosphere heat energy in the form of infrared radiation. But as indicated schematically in Fig. 6, gases such as water vapor, CO2 and CH4 in the atmosphere absorb some of this infrared radiation from the Earth’s surface, and then they re-emit infrared radiation in all directions, downward back to the surface as well as upward to the upper atmosphere.
The greenhouse gases do not absorb the visible and ultraviolet radiation from the Sun that directly heats the Earth. When greenhouse gas concentrations increase significantly, they upset the equilibrium by returning more infrared energy to Earth’s surface, heating the planet. This basic physics was already predicted in 1896 by Swedish physicist Svante Arrhenius, and is by now very well established.
As increasing concentrations of greenhouse gases in the lower atmosphere absorb energy radiated from Earth’s surface, they reduce the amount of infrared radiation flowing outward to the upper atmosphere. They do so over well-defined ranges of radiation wavelength characteristic for each type of greenhouse gas. For example, even though CO2 concentrations may increase in the stratosphere, those molecules are bathed in less energy within their absorption wavelength ranges, since much of that energy has already been filtered out and re-radiated downward by the CO2 molecules in the troposphere. The stratosphere molecules still occasionally get excited by collisions with other molecules, and they subsequently emit radiation. But as they emit more than they absorb, the stratosphere cools. But the troposphere undergoes net warming from the extra energy absorbed and re-radiated by the increased CO2 concentration.
How do scientists know that the recent warming trends can be attributed to increased greenhouse gas concentrations? Well, first of all there is the clear correlation of the late 20th century global temperature increase seen in Fig. 4 with the comparable increase shown in Fig. 7 for measured CO2 concentrations in the atmosphere. The latter increase is driven, in turn, by emissions of CO2 from human burning of fossil fuels, as also shown in Fig. 7.
In addition, there are independent data such as those shown in Figs. 8 and 9. Figure 8 shows the change in the spectrum of infrared radiation escaping to space as measured by satellites in 1970 and 1996. The largest negative dips seen at the left edge and near the right edge of the plot demonstrate that outgoing radiation has been removed precisely within the absorption bands characteristic of CO2 and CH4. Those results again argue for the increased concentrations of these greenhouse gases over the second half of the 20th century.
Figure 9 shows that the isotopic ratio of carbon-13 to carbon-12 has been steadily decreasing in the corals of the Great Barrier Reef during the second half of the 20th century. This is consistent with increasing carbon content in the seas from fossil fuel burning, which preferentially releases carbon-12, in comparison with natural carbon sources.
The Heartland booklet admits the buildup of greenhouse gases, but they make the following claim: “In ice core samples, changes in temperature precede parallel changes in atmospheric CO2 by several hundred years; also, temperature and CO2 are uncoupled through lengthy portions of the historical and geological records; therefore CO2 cannot be the primary forcing agent for most temperature changes.” The first two statements are misleading, as explained below, and the third statement does not follow even if the first two were fully true. As we have seen, there are many potential climate drivers, and the physics of infrared radiation absorption clearly identifies greenhouse gas concentrations in the atmosphere as one of these, though not the one that has initially driven emergences from past ice ages.
As seen in Fig. 1, the correlation between temperature and CO2 levels is very strong over the past million years or so. But a closer examination does reveal that at the start of a number of past deglaciation periods, CO2 buildup in the atmosphere lags behind the initial temperature rise by several hundred years. That is because the initial temperature rise coming out of an ice age is driven by Earth orbital changes that enhance heating from the Sun. But that enhanced heating cannot explain the magnitude of the subsequent global temperature increases.
The initial temperature rise following an ice age heats Earth’s oceans. CO2 is less soluble in warmer oceans, and therefore more of it is released into the atmosphere. Once there, the enhanced CO2 concentration absorbs infrared radiation from the Earth, and thereby amplifies the planet’s warming. In successful climate models of these past deglaciation periods, 90% of the total warming observed over millennia can be attributed to the greenhouse gas amplification. In fact, this amplification effect helps to provide a historical constraint on the sensitivity of Earth’s temperature to atmospheric greenhouse gas concentrations, as will be discussed further in subsection 4c.
The time sequence of temperature and CO2 increases has recently been mapped in some detail [Shakun, et al., 2012] for the emergence from the last ice age about 20,000 years ago, with data shown in Fig. 10. These authors were able to use not only temperatures deduced from Antarctic ice cores, but also northern hemisphere and global temperatures reconstructed from Greenland ice cores, ocean and lake floor sediments, etc.
Shakun, et al. used detailed global climate models to account for the data shown in Fig. 10. According to the successful model, the likely sequence of events was as follows. The orbital changes increase solar heating most at high latitudes, where the initial effect is melting of Arctic and Antarctic ice. The added water disrupts normal ocean circulation patterns, and appears to have warmed southern hemisphere oceans first. The increased CO2 emission into the atmosphere from these warmer oceans then gives rise to additional global warming by the amplification mechanism mentioned above.
The increase in CO2 concentrations then appears to have slightly lagged behind initial southern hemisphere warming, but to have led and caused much of the northern hemisphere warming. These model results are summarized in Fig. 11, which shows time lags and leads determined in 1000 independent simulation runs of the model code used by Shakun, et al. The extent of the time difference between southern hemisphere temperature increases and CO2 increases is not very well constrained by the data of Fig. 10. Consequently, the orange shaded band in Fig. 11 spans a wide range of time differences, but in nearly all of the simulation runs, CO2 increases follow southern hemisphere temperature increases resulting from the Earth orbit changes. In contrast, the northern hemisphere time delays fall in a narrower band (blue shaded region in Fig. 11), with temperature increases following CO2 increases by typically 700 years. When southern and northern hemisphere results are combined to track global temperature increases, these also occur after CO2 increases by typically 460 years (gray shaded band in background of Fig. 11).
The IPCC conclusion that greenhouse gas emissions not only can drive, but are currently driving, global temperature increases is a finding based on such detailed climate modeling, which will be dealt with in more detail in Part II of this blog post. But for the Heartland booklet to label this finding as an unsupported postulate is deliberately misleading.
And what of Heartland’s last claimed “postulate” regarding whether projected global warming would cause net harm to the biosphere and human well-being? The potential impacts of climate change are diverse and challenging to predict. In the IPCC framework, these impacts are judged by a separate working group from the one that evaluates the physical basis for climate change. WG II “assesses the vulnerability of socio-economic and natural systems to climate change, negative and positive consequences of climate change, and options for adapting to it. It also takes into consideration the inter-relationship between vulnerability, adaptation and sustainable development. The assessed information is considered by sectors (water resources; ecosystems; food & forests; coastal systems; industry; human health) and regions (Africa; Asia; Australia & New Zealand; Europe; Latin America; North America; Polar Regions; Small Islands).”
WG II has identified a small number of potential beneficial impacts of moderate global warming, among the many sectors and regions it considers. But these are far outweighed globally by carefully considered (not postulated) negative impacts pooh-poohed in the Heartland booklet. These include massive melting of ice at high latitudes, mass human migrations caused by coastal flooding, food and water shortages caused by severe weather (droughts or floods) in different regions, severe ocean ecosystem damage, eventually mass species extinctions, and secondary consequences of all of these changes. Predicting precisely where the various negative impacts will become severe as a function of global temperature rise is not an exact science. But the consensus view is that adaptability is still within the grasp of most species for increases below 2ºC.
We will return to consider potential climate change consequences in more detail in Section 6 (Part III) of this blog post. But at this point, we may ask whether there is anything in Earth’s historical record to justify the serious concerns highlighted by the IPCC. In principle, one might expect species on Earth to evolve or migrate in order to adapt to climate changes. But evolution of the species is an inherently slow process occurring over many generations, and mass species migrations are also slow, while the climate changes we are witnessing today are incredibly rapid by historical standards.
The best historical analog available for today’s rapid increase in greenhouse gas concentrations is from occasional periods of massive volcanic eruptions in so-called Large Igneous Provinces (LIPs). These eruption periods injected large amounts of CO2 and CH4 into Earth’s global atmosphere, at a rate that is historically high but still considerably slower than what humans are presently doing by fossil fuel burning. Figure 12 shows a worrisome apparent correlation between the timing of these LIP eruption periods and the occurrence of mass extinctions determined from fossil records. Also correlated with these events were serious depletions of oxygen in Earth’s oceans. In the case of the extinction ending the Permian era some 250 million years ago, as much as 90% of the living marine species on Earth were extinguished.
Climatic conditions were quite different several hundred million years ago: base levels of greenhouse gas concentrations were much higher than today, but the Sun was correspondingly weaker. Nonetheless, the distinct possibility that many mass extinction events were caused, at least in part, by rapid increases in greenhouse gas concentrations should certainly be taken as a precautionary tale today. In contrast, there do not appear to have been mass extinction events associated with emergence from past ice ages, when global temperatures have increased typically by 4-8ºC, but over periods of typically thousands of years (e.g., see Fig. 10).
Let’s recap quickly what we’ve seen so far. Of the 12 figures included in this subsection, the only one included or even discussed in the Heartland booklet is the intentionally misleading Fig. 2, which simply eliminates the 20th century. The other eleven figures included here are merely samples of enormous quantities of data that are easily accessible to anyone interested, and with which self-proclaimed climate experts, such as the Heartland booklet authors, should be quite familiar. None of the historical evidence supporting IPCC findings is treated in the Heartland booklet. That extreme cherry-picking is what enables the authors to misidentify these findings as unsupported postulates. There is, in fact, a lot of data that establishes ongoing climate change as due in largest part to human activity emitting greenhouse gases, and that causes serious concern about potential impacts of these climate changes, even before one begins to discuss detailed global climate model projections.
Some suggestions for leading student discussions of material in this subsection:
- Ask students what conclusions they might draw from the data in Fig. 1.
- Ask students what bearing the comparison of Figs. 2 and 3 has on the Heartland booklet’s claim that late 20th century warming is not at all unusual.
- Ask students what they would expect for the content of Fig. 5 if temperature increases were primarily caused by increased energy received from the Sun: would days or nights warm more? Would both lower and upper atmosphere warm?
- Ask students what conclusions they might draw, or what further information they would like to see, from comparing Figs. 3 and 7.
- Ask students to speculate about what natural occurrences in Earth’s history might have increased carbon dioxide and methane in the atmosphere as rapidly as human burning of fossil fuels has done over the past 60 years.
- Discuss with students the differences between postulates and research findings.