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Scientific Disagreement about Climate Change

By Dr. Jeff Mirus (bio - articles - email) | Aug 22, 2012

In my previous essays on the moral dimensions of climate change (see The Moral Downside of Climate Change and Climate Change and Moral Knowledge) I promised to write something about the actual scientific disagreements concerning climate change, for this is a case where moral judgment must depend on scientific evidence. In preparing to address these issues, I learned that a scientist who is also a friend, Thomas B. Fowler, had recently completed a significant study of this precise matter, in much the same way as he did a few years ago on questions surrounding human origins in his outstanding book The Evolution Controversy (see Evolution: The Missing Link). Fowler points out that, among scientists, disputes over climate change are far more widespread and extensive than disputes over evolution, and that climate change seems to have replaced evolution as the most culturally and politically divisive arena of scientific research in the contemporary world.

Fowler holds a doctorate in Physics and has worked in the field of systems analysis for most of his life. He is something of a Renaissance man, with an undergraduate degree in Philosophy. One of his side projects over the years has been to promote awareness of the work of the brilliant Spanish Catholic philosopher, Xavier Zubiri (see His breadth of knowledge, attention to proper scientific method, and analytical powers never fail to impress. In the study of the climate change controversy, he has turned all these to good advantage in a major article which is currently pending publication (I will call attention to it when it becomes available). While I can only touch lightly on the various sticking points in this space, I owe most of what follows to Fowler’s far more extensive work.

Clarifying the Topic

The first order of business is to clarify what we are talking about. We need not airily dismiss anyone as a “climate change denier” (like a “holocaust denier”), because nobody denies that climate change occurs, is occurring now, and in fact occurs constantly. Rather, the entire argument revolves around this proposition: Human activity is causing the earth’s climate to warm dangerously. This is called anthropogenic global warming.

Certain aspects of this key issue are non-controversial. First, climate change is constantly occurring. Second, global temperatures rose during the intense period of modern study in which today’s climate projections were initially generated, between about 1980 and 2000. Third, carbon dioxide and other greenhouse gases cause atmospheric heating and have increased by about thirty percent since 1900. Fourth, human activity (namely, the burning of fossil fuels) is the principle source of the increase in greenhouse gases.

What is controversial is how this information fits together and what, if anything, it means. First, there is disagreement about whether we can safely translate a correlation between rising temperatures and rising greenhouse gases into a definitive cause. Part of this disagreement rests on simple logic, but we also need to notice that particular changes in our atmosphere cause “feedback loops”, or related changes which either amplify or diminish the impact of the initial change; there is significant debate over whether the feedback loop of increased carbon dioxide and other greenhouse gases results in amplification or diminution. Second, there is disagreement on the role played by other factors and on how the climate system works overall, or whether we understand it sufficiently to make reasonable projections. Finally, there is disagreement over whether what we are experiencing now is outside the normal range of climatic change compatible with human flourishing.

Looking Backwards over Time: What is Normal?

To try to figure out whether current trends are abnormal or fit within a normal range, climate scientists look backwards over time to see how much variation there has been. One of the great difficulties with this is that small climate cycles may be hundreds or thousands of years long and the larger cycles of which they are a part may be measured in tens of thousands of years (as studies of ice core samples demonstrate). This means that a recent and brief rise (or fall) of temperatures does not necessarily indicate anything about a longer term cycle. All of this is exacerbated by the fact that we have accurate temperature records going back only about a century; before that, temperature information must be extrapolated from other data, such as tree ring growth patterns (which don’t really correlate well with temperature) and ice core samples (going back much farther). Moreover, when one considers that we need an immense collection of consistent data points (same time, same place, each year, around the globe, tossing out local anomalies), the available data is even more limited. We have had the inclination and ability to collect such data and the computers to analyze and model it only for about a generation. All of this makes climate modeling and prediction very risky, impossible to define as “settled science”.

Nonetheless, it is the effort to chart the trajectory and meaning of current data which gave rise to the plotting of past temperature data in the famous “hockey stick” graph in 1999. The hockey stick shape (lying along the back of the stick with the blade pointing up at the right end) showed (in direct contradiction to written records from various periods) that temperatures were basically flat for the past thousand years until the 20th century, when temperatures soared. While widely and uncritically used for quite some time and still cited by global warming advocates, most scientists (including those at the United Nations) have now backed away from the hockey stick. Modified and updated versions of the temperature graph since 800 AD clearly show, for example, that the Medieval Warm Period (roughly 800 – 1250 AD) peaked well above anything we are experiencing or projecting today. Moreover, a similar graph over the period beginning in 3000 BC shows that the maximums of both the Late Bronze Age and the Roman period were substantially higher than even the Medieval Warm Period.

The hockey stick model was developed by Michael Mann of the University of Virginia using methodologies and data that were defective from the first. The essence of scientific progress is the public availability of data and methods so that other scientists can either critique or reproduce results. It casts interesting light on the prejudices and inclinations of the climatology community that Mann never made his data and methodology available and that there was little interest for quite a long time in reviewing and challenging this model. Still, it is important to note that discrediting the hockey stick model does not discredit the fact that global temperatures have risen recently, especially during the past thirty-five years. It simply alters our perception of the normal range of variation compatible with human flourishing, a perspective gained by looking back in time.

Projecting Forward: Are We Facing Disaster?

In order to determine what is likely to happen to our climate, of course, climatologists must look forward. They must gather as much data as they can relating to all significant variables, they must describe mathematical relationships among the different variables, and then they must project the likely outcome based on current measurable trends. It goes without saying that this is fraught with difficulty. Consider, for example, the likelihood of accurately forecasting the stock market with even the most highly developed computer models. Yet climate is far more complex than the world of stocks and bonds.

Therefore it is no surprise that scientists disagree about the ultimate meaning of rising levels of carbon dioxide in the earth’s atmosphere. Without the greenhouse effect on earth, our planet would be far colder (projections suggest average temperatures of -18° C (or 0° F) than what we actually have (15° C or 59° F). The sun warms the earth, and what is warmed begins to radiate energy, but this heat energy is largely trapped by the atmosphere, making the earth a greenhouse—with very important and obviously desirable results for life. But if carbon dioxide or other greenhouse gases increase too much, what will happen?

The ultimate result is not clear, and for several reasons. First, greenhouse gases are a very small part of our atmosphere, so even substantial percentage changes are in reality relatively tiny. Taken only in their immediate effects, these gases contribute only about one percent of the heating power of the sun. This suggests that other variables may be far more important. Second, while carbon dioxide does immediately force rises in temperature, it also creates other conditions (feedback loops) which may well diminish temperature. Long-term data collected by NOAA shows a correlation between carbon dioxide and warmth, but in a way that suggests the feedback mechanisms initially add to the warming but then shift into a cooling mode. Thus (for example) initial warmth may stimulate greater biological activity, which adds even more carbon dioxide, but at a certain point this may cause an increase in our cloud cover, which dramatically reduces temperatures, causing a reversal of this process.

The most widely accepted projections use a model which multiplies the initial  direct effect of carbon dioxide by a factor of three, leading the UN’s International Panel on Climate Change to estimate in its 2007 report that temperatures would increase by two-tenths of a degree Celsius per decade over the next twenty years (until 2027), given reasonable assumptions consistent with current data. Thus, even though the IPCC backed away from the hockey stick model, the organization stood by by its collective work which predicts rising temperatures, and stood by its analysis that this change will be caused primarily by human burning of fossil fuels.

The IPCC and Current Trends

This brings us, inevitably, to an assessment of the International Panel on Climate Change. The organization issues periodic reports, which are publicly available. The latest report is the fourth, issued in 2007. There can be no question that this UN-orchestrated effort constitutes the largest and most comprehensive climatology operation in the world. All scientists, even those who disagree with IPCC conclusions and projections, recognize that the data amassed by the IPCC is genuinely impressive, and of great value.

Nonetheless, the IPCC is not without its own problems. The first of these is that disagreements within the IPCC itself are hidden, because the IPCC does not publish dissenting viewpoints. Therefore, the impression given to outside scientists is that the IPCC’s work represents genuinely “settled science”, rather than uneasy conclusions that are at least to some extent controversial within the IPCC itself. This can act as a brake on the work of other scientists who might wish to critically examine IPCC data or IPCC assumptions or IPCC analysis and projections.

Moreover, in a series of widely-publicized “scandals” that may or may not cast doubt on the IPCC’s level of competence, several significant problems have already been discovered in the 2007 report: (1) The IPCC had to retract incorrect statements about the melting of Himalayan ice; (2) The report contained claims about disappearing ice based on a student dissertation and an article in a mountaineering magazine; (3) The report relied on papers by the World Wildlife Foundation (an advocacy organization) for its claims that global warming could kill off 40% of the rainforest; (4) And of course the IPCC deliberately backpedaled on the hockey stick which, in an earlier report, it had insisted was a crucial piece of evidence for anthropogenic global warming and its dangers.

Far more important than any of this is the simple fact that if the predominant projections of rising temperatures were accurate, then temperatures should have risen not only between 1980 and 2000, but after 2000 as well. Yet the entire scientific community now knows, and freely admits, that temperatures have been stable since 2000. The trend noticed in the third quarter of the twentieth century has not, thus far, continued into the twenty-first. Though what this means may be far from clear, at the very least it suggests that, even among scientists, the climate change situation itself is far from clear.


The dilemma is this: If anthropogenic global warming is a real concern, and we do nothing, we could all suffer unpleasant consequences which, as has often been noted, will inevitably fall hardest upon the poor. But if we act when there is no significant reason for concern, we would commit ourselves to a hugely expensive program of eliminating fossil fuels to correct a problem we do not have, a program which would also cause many serious hardships. Once again, the hardships would fall most heavily on the poor. What this means is that scientists have a very significant moral obligation to get things right, to be unswayed by political pressure, cultural status, funding opportunities, reluctance to admit error, or even a too facile acceptance by many of the research done by only a few. This scientific certainty does not yet exist, and probably cannot yet exist. Moreover, given current flat temperature trends and the recent periodic decline in sun spot activity (a new topic, but one that seems to correlate very strongly with temperature change on earth), it is likely that the next ten years will tell us a good deal more.

It would seem that prudence demands patience, and as I have argued elsewhere, there is a serious “moral downside” to creating a moral cause which is largely lacking in moral content. Meanwhile, there are plenty of well-established environmental concerns to work on, not to mention many more pressing problems in developing an authentic culture of life.

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  • Posted by: FredC - Aug. 30, 2012 11:50 AM ET USA

    NASA and the EPA have large groups that investigate global warming. If they were ever to find that there is no threat of global warming, the government employees could be out of work. The work that NASA contracts out to researchers goes to those who support the theory that global warming is strongly influenced by man. If the contrarians were funded at the same level as the proponents, I might take the proponents more seriously.

  • Posted by: bkmajer3729 - Aug. 27, 2012 7:54 PM ET USA

    filioque has this nailed! No one is denying that something is going on. The problem is there is no sigificant evidence to "connect the dots" to the conclusion "it must be caused by humans". Science is about observation and experimentation to confirm/deny the hypotheses resulting from the observation. I don't care if they're PhDs or not; if they are not doing science, then they have some other motive besides truth. Regarding the sunspot comment, again absolutely on target.

  • Posted by: filioque - Aug. 27, 2012 10:47 AM ET USA

    @tiomax6441: Your position is purely an argument from authority, but science is not about consensus or votes. The only thing that counts is evidence. One man with evidence can prove a million wrong. Read and learn: e.g.,; or; or Once you start to look past the "consensus" you will find a wealth of information to make you a skeptic.

  • Posted by: Randal Mandock - Aug. 25, 2012 3:53 PM ET USA

    According to the Danish National Space Institute, solar wind diverts cosmic rays from entering our atmosphere. If cosmic rays lead to increased production of cloud condensation nuclei, as found in this agency's peer-reviewed publications, then reduction in cosmic ray intensity at the outer atmosphere due to increased solar wind will result in fewer cloudy days and warmer global temperatures. Thanks go to Bruno for his sunspot comment. Did anyone notice the record high temperatures this year?

  • Posted by: tiomax6441 - Aug. 25, 2012 2:42 PM ET USA

    When one lists the top best 50 climatologists (Those with a Phd in climatology and who publish in peer reviewed periodicals) you only get two deniers (4%). When you take the top 100 you only get one more denier (3%). During the 1950s and 1960s tobacco companies hired doctors to write reports proving that tobacco was harmless. Big oil and big coal are doing the same thing now for AGW. Isn't it time that we heeded the good climatologists? We already have climatic refugees.

  • Posted by: filioque - Aug. 24, 2012 11:20 PM ET USA

    Very good summary. The fact is that we have no evidence to justify the conclusion that anything unusual is happening. And no one has published evidence that human-generated CO2 causes dangerous warming. The much-vaunted models contain only suppositions about feed-backs that are looking shakier and shakier. They are not evidence, except perhaps of overstated positions. We don't know enough yet to justify doing anything, because the remedies will certainly do serious harm and possibly no good.

  • Posted by: bruno - Aug. 24, 2012 10:10 PM ET USA

    Sunspot activity has recently had an unexpected spike not quite in keeping with the periodic behavior expected. reports 0 days thus far in 2012 without a sunspot! Coronal Mass Ejections (CMEs) could be extremely disruptive of communications and weather, but no one would dream of suggesting a human cause. Is this why it is more likely to be ignored, I wonder? FYI, the latest plume of solar wind is expected to reach us in two days.

  • Posted by: Randal Mandock - Aug. 24, 2012 1:31 AM ET USA

    "...projections suggest average temperatures of -18° C." It's not exactly a projection. It's actually straightforward physics. Assuming the validity of the Stefan-Boltzmann law, you can determine the effective temperature of the earth (nearly a blackbody) by calculating the heating of the earth by the sun: 1/4 the solar constant times the earth's absorptivity. Next divide by the Stephan-Boltzmann constant and take the 4th root of the quotient: ((0.7*1362/4)/5.67E-8)**0.25 = 255K = -18 degrees C.

  • Posted by: jjen009 - Aug. 23, 2012 5:42 PM ET USA

    It seems to me there is an additional concern. Supposing anthropogenic client change were a settled conclusion - is it clear that we (whoever 'we' may be :-)) can be confident about the results of whatever action 'we' take, be it reducing carbon emissions or anything else?

  • Posted by: the.dymeks9646 - Aug. 23, 2012 1:44 PM ET USA

    Well done. Unfortunately, many people are too committed to their climate beliefs, and in being so, are living the moral downside of being deceived and closing their eyes to an expanded and healthy view of the mysteries of God's creation. BTW, when ice melts it releases oxygen; and, water vapor is a far more effective and prevalent green house gas. What's your water vapor footprint?

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