Divided Science and Unfounded Policy

Global Warming: Part I

By David W. Riggs, Ph.D., Senior Fellow, Economic and Environmental Studies, Center of the American Experiment


Bruce Babbitt, Secretary of the Interior, recently remarked that, “climate change is the largest, most pervasive and ominous threat that we have ever confronted in this civilization.”1 Dangers such as encroachments on individual freedom and human rights notwithstanding, it is no coincidence that a statement like this comes just prior to a conference where 160 nations will be convening to discuss and possibly act on potential global climate change.

The apparent objective of the Kyoto conference is to obtain a binding commitment from industrialized nations to reduce their carbon dioxide emissions and other greenhouse gases to specific targets by specific dates. President Clinton recently unveiled a proposal for industrialized nations to reduce greenhouse gas emissions to 1990 levels between 2008 and 2012. Likewise, Japan and the European Union have similar proposals to reduce greenhouse gas emissions 5 and 15 percent, respectively, from 1990 levels within the next 10 to 20 years.

The climate control proposals are based on the premise that global warming is real and caused by human activity. The proposals also assume that binding commitments will reduce greenhouse gas emissions worldwide and prevent global warming. The truth of the matter is that each of these propositions is very much in doubt.

This briefing is the first in a three-part series that addresses potential global climate change. The purpose of the series is to increase the public’s understanding of the true scientific and economic underpinnings of the global climate change debate. It’s also to provide an assessment of proposed policies and their implications for Minnesota.

This segment presents an overview of general scientific issues. In Part II, which will follow shortly, the economic consequences of greenhouse gas emission-reduction policy will be addressed, with special emphasis placed on why Minnesotans should care about the Kyoto treaty. And Part III will look at why a global climate treaty is emerging and what a reasonable course of action should be to potential global climate change.

The Greenhouse Effect and Uncertainty

The greenhouse effect is a naturally occurring phenomenon where the sun’s energy, in the form of solar radiation, enters the earth’s atmosphere and that energy is converted into heat. Greenhouse gases – e.g., water vapor, carbon dioxide, and methane – absorb this heat and further warm the earth’s atmosphere. There is little controversy in the theory of greenhouse gases determining climate: Holding all else constant, an increase in greenhouse gas emissions will increase temperature. The fact that the average surface temperature on earth is 59 degrees Fahrenheit instead of freezing temperatures is attributed to the greenhouse effect. And so, it is presumed by some that further increases in greenhouse gases, especially carbon dioxide, will increase average surface temperature. The evidence, however, casts doubt on this presumption and shows that our climate system is not that simple.

To begin, the greenhouse effect does not operate in isolation. If it did the average surface temperature would be a balmy 170 degrees Fahrenheit. That is, the greenhouse effect is only about 25 percent of its full potential.2 Weather systems are very complex and scientists have only just begun to understand their dynamic nature. This is especially true when trying to isolate the impact of greenhouse gases on climate.

The uncertainty surrounding the impact of the greenhouse effect is a little like trying to explain how to lose weight by exercising more. The general theory goes: If people exercise more say they increase the number of miles jogged per week – then they will lose weight. But as all of us who have engaged in this little experiment can attest, the empirical evidence will only support the theory if other critical factors are held constant: namely, caloric intake, age, sex, heredity, etc. These other critical factors can have a significant impact in determining weight-loss and, therefore, on the effectiveness of exercise in determining weight-loss. And so, to properly test the theory, one must identify and incorporate these other factors into the experiment.

Just like the weight-loss example, there are other critical factors that determine global climate in addition to the greenhouse effect. It is the interplay of these other critical factors known as “feedback effects” which fuel the global climate change debate. (And yes, despite how the popular press frequently portrays the issue,3 there is considerable ongoing scientific debate.)

Changes in water vapor and cloud cover are some of the feedback effects which contribute to the controversy. Dr. Roy Spencer, Senior Scientist for Climate Studies at NASA’s Marshall Space Flight Center, states the crux of the scientific uncertainty debate: “[W]e know so little about cloud feedback and water vapor feedback, which are probably the most important feedbacks to carbon dioxide; that for me at least, I think the safest thing to assume is that the earth will continue to do what it does best: that is reject excess heat.”4

The complexity of the climate system makes it difficult to distinguish human-induced temperature changes from natural temperature fluctuations. Greenhouse gases comprise only about 1 percent of our atmosphere, most of which is nitrogen and oxygen. Of that 1 percent, the most abundant greenhouse gas is water vapor, which accounts for about 90 percent of all greenhouse gases in the atmosphere. The importance of water vapor – which man has no control over – obviously is substantial. If other greenhouse gases such as carbon dioxide and methane were to disappear – that is a 100 percent reduction from current concentrations – we would still be left with over 90 to 98 percent of the greenhouse effect.5 Because the climate is always undergoing change, the proposed policies that strive to reduce carbon dioxide emissions by only about 10 percent from current levels are likely to have a negligible effect on global climate relative to the climate’s natural variability.

In short, when it comes to the science of global warming, a great deal of uncertainty remains. The uncertainty does not, however, lie with the “theory” of the greenhouse effect; instead, it lies with how other factors – feedback effects – interact with the greenhouse effect and whether changes in human-generated greenhouse gas emissions cause significant temperature increases in comparison to natural fluctuations in the temperature levels.

A Scientific Consensus?

Recall that only a few decades ago some scientists were predicting that the earth’s climate would cool – the coming ice-age.6 Likewise, note that some scientists still recognize a cooling potential. Global warming became the concern in the 1980s as some scientists predicted dramatic increases in temperatures leading to the melting of polar ice caps, rising sea levels, and other catastrophic events. Recently, global warming predictions have been heralded in the popular press as authoritative because of a scientific consensus consisting of 2,500 scientists from the Intergovernmental Panel on Climate Change (IPCC).7 However, a closer look at the IPCC’s Scienc

e Report reveals that several hundred scientists are listed as contributors and reviewers, but it does not say whether they agree with the study’s assertions.8 Moreover, the “Summary for Policymakers” section in the IPCC report was put together by a handful of people and appears to be more of a political document reflecting their government’s position than a statement of scientific consensus.9

In light of this, let’s explore the major points of contention in the so-called “consensus.” The science of global climate change is composed of two parts: actual climate data and climate forecasting.

The actual global temperature change data are mostly from land-based temperature measurements and satellites. The land-based temperature measurements show about a 1 degree Fahrenheit increase in average global temperature over the last 100 years. Most of the temperature increase occurred prior to 1940, while most of the increases in greenhouse gas emissions occurred after 1940. Based on the analysis of these data, most scientists conclude – including Prof. Bert Bolin, Chairman of the IPCC – that this temperature increase was natural in origin, resulting from the earth recovering from a “little ice age.” Adding to the uncertainty, the 18 years of satellite data – which by most standards provide the best estimates of temperature change – do not support the theory of global warming; in fact, the satellite data show a slight cooling trend.

In addition, much has been written about a statement in the Summary for Policymakers: “[T]he balance of evidence suggests that there is a discernible human influence on global climate.”10 Notice that this vague statement is merely a suggestion, not a conclusion. The caveat that precedes the statement is almost always left out: “Our ability to quantify the human influence on global climate is currently limited because . . . there are uncertainties in key factors.”11

Moreover, the statement is presumably based on Section 8, “Detection of Climate Change and Attribution of Causes” in the IPCC report. However, the closest Section 8 comes to this statement is a more moderate version: “Taken together, these results point towards a human influence on global climate.”12 The report then continues with an explanation of the uncertainties that remain, such as the aforementioned feedback effects. Hence, when actual data are analyzed, a scientific consensus supporting the theory of global warming and a “discernible human influence on climate change” does not follow.

Results from global climate forecasting models which proponents of the global warming theory rely most heavily upon also do not lead to any consensus. The IPCC in 1990 forecasted a 0.3 degree Centigrade increase per decade. Just two years later, the IPCC lowered this estimate slightly after learning more about feedback effects. The IPCC’s latest 1996 estimates show an increase of 0.18 degree Centigrade per decade.

Because uncertainty exists as to how the climate system responds to change, the forecasting models do not properly incorporate feedback mechanisms. Simply, there is a difference between how the atmosphere works and how it is “modeled” to work.

For example, with increases in greenhouse gases, cloud cover may increase which would then reflect more solar radiation, decreasing the amount of available, absorbable heat. Many of the forecasting models, on the other hand, have cloud cover decreasing, which enhances the greenhouse effect and exaggerates forecasted temperature increases. Noted climatologist Dr. Roy Spencer states that the predictive models that forecast global warming do not do a very good job at dealing with feedback effects.13 Moreover, a downward trend in forecasted temperature estimates is evident as scientists learn more about the climate system and incorporate this knowledge into their models.

In a recent national survey conducted of state and regional climatologists, 58 percent disagreed with the statement that, “the overwhelming balance of evidence and scientific opinion . . . is that global warming is for real [and that] there is ample evidence that human activities are already disrupting the global climate.”14 Furthermore, some 100 independent scientists who take the global climate-change issue seriously – signed, in 1995, the “Leipzig Declaration” that expresses their skepticism. The essence of their doubts is summarized in the following passage:

[I]t has become increasingly clear that – contrary to conventional wisdom – there does not exist today a general scientific consensus about the importance of greenhouse warming from rising levels of carbon dioxide. On the contrary, most scientists now accept the fact that actual observations from earth satellites show no climate warming whatsoever. And to match this fact, the mathematical climate models are becoming more realistic and are forecasting temperature increases that are only 30 percent of what was considered the “best” value just four years ago.15

Effective Environmental Policy?

Despite all the uncertainties and evidence refuting the global warming theory, global warming proponents race to Kyoto with proposed policies to reduce greenhouse gas emissions. Through these proposed policies, international governmental bodies are attempting to engineer the proper amount of greenhouse gases in our atmosphere. But the truth of the matter is that nobody knows what that proper amount is, or how much carbon dioxide is dangerous or not dangerous. Let’s keep in mind that some greenhouse gases in our atmosphere are very beneficial; that without them the earth’s temperature would be similar to the moon’s, where no greenhouse gases are found. We simply do not know if more or less carbon dioxide in our atmosphere will be beneficial.

Moreover, if we assume for the moment that less carbon dioxide is beneficial, the proposed policies only delay the increases in carbon dioxide concentration. Global climate change is determined, in part, by changes in the concentration of carbon dioxide in the atmosphere, while changes in carbon dioxide emissions determine its concentration. Carbon dioxide emissions can remain in the atmosphere 50 to 200 years after being released. Hence, concentrations of carbon dioxide in the atmosphere are determined cumulatively over a very long period of time.

Because emissions remain in the atmosphere for such a long time, the proposed reductions of greenhouse gas emissions to 1990 levels will not stabilize greenhouse gas concentrations at low levels. Instead, reducing greenhouse gas emissions to 1990 levels will merely defer the increases in greenhouse gas concentrations by, at most, a couple of decades.16

Essentially, greenhouse gas emission-reduction policies do not have a scientifically-based environmental objective; it is not clear if carbon dioxide concentrations should be higher or lower. Furthermore, the proposed policies’ chosen objective – carbon dioxide emission-reduction – is not likely to generate environmentally significant reductions in greenhouse gas concentrations. Looking again to the Leipzig Declaration, it urges caution in moving forward with greenhouse gas emission-reduction policies based on our current state of knowledge:

Although we understand the motivation to eliminate what are perceived to be the driving forces behind a potential climate change, we believe this approach may be dangerously simplistic. Based on the evidence available to us, we cannot subscribe to the so-called “scientific consensus” that envisages climate catastrophes and advocates hasty actions.17


The science of global climate change is very complex and the notion that the proposed policies for the Kyoto conference will somehow “save the planet” is simply unfounded. Before we leap forward with policy that will restrict our energy use, we must base our decisions on sound science.

  • Proposed greenhouse gas emission-reduction policies are not rooted in scientific analysis.
  • A scientific consensus on global warming does not exist and scientific uncertainty remains with respect to how feedbacks in the atmosphere respond to changes in greenhouse gases.
  • As we learn more about the atmosphere’s ability to adjust, the estimates of global temperature increases in forecasting models are continually being reduced. The reality is that the more scientists study climate, the more they learn of its incredible complexity.
  • Temperature increases shown in land-based measurements are attributed to natural (not human-caused) fluctuations. And 18 years of satellite data show a slight cooling trend.
  • The proposed policies only delay increases in greenhouse gas concentrations.
  • The proposed policies call “for achieving a concentration of greenhouse gases that avoids ‘dangerous interference’ with the climate system. The trouble is that no one has a clue as to what level of carbon dioxide is dangerous – or non-dangerous . . . Higher concentrations of carbon dioxide may be beneficial. We simply do not know.”18 


1 Babbitt, Bruce. “Global Warming: A Call to Action on Climate Change.” http://www.doi.gov/secretary.

2 Lindzen, Richard S. “Global Warming: The Origin and Nature of the Alleged Scientific Consensus.” Regulation. Vol. 15 (2), 1992.

3 See, for example, Lemonick, Michael D. “Courting Disaster.” Time. Vol. 150 (18), November 3, 1997.

4 Spencer, Roy. “The State of Climate Change Science.” Presentation given at the Competitive Enterprise Institute’s Global Warming Conference: The Costs of Kyoto. Washington, DC: National Press Club, July 15, 1997.

5 Lindzen, supra note 2.

6 See, for example, Schneider, S. H. The Genesis Strategy: Climate and Global Survival. New York: Plenum Press, 1976; and Ponte, L. The Cooling. Englewood Cliffs, NJ: Prentice Hall, Inc., 1976.

7 Babbitt, Bruce. “Melting Glaciers are Call to Act on Global Warming.” Star Tribune. Sect. A33, November 16, 1997.

8 Intergovernmental Panel on Climate Change. Climate Change 1995: The Science of Climate Change. New York, NY: Cambridge University Press. 1996.

9 Ibid., pp. 1-7.

10 Ibid., p. 5.

11 Ibid., p. 5.

12 Ibid., p. 412.

13 Spencer, supra note 4.

14 American Viewpoint, Inc. “Citizens for a Sound Economy, Survey of State and Regional Climatologists.” Alexandria, VA, Sept.-Oct. 1997.

15 The Leipzig Declaration on Global Climate Change. The International Symposium on the Greenhouse Controversy, held in Leipzig, Germany, November 9-10, 1995.

16 Reuter, Frederick H. Framing a Coherent Climate Change Policy. St. Louis, MO: Center for the Study of American Business, October 1997.

17 Leipzig, supra note 15.

18 Singer, Fred S. “Trick or Treaty: An Energy Tax in Disguise.” The Washington Times. July 1, 1997.