One of the claims continually put forth by the media about global warming is that there is a “scientific consensus” about it. So let’s take a look at just what is a “scientific consensus” and how does the concept relate to the debates about climate change.

At the start we must distinguish between scientific fact and scientific consensus. A scientific fact was defined by geologist Stephen Jay Gould in a Time magazine interview (Aug. 15, 1999) as “a proposition affirmed to such a high degree that it would be perverse” not to assent to it. In this sense it is a fact, for example, that the noble elements are naturally inactive in combining with other elements. The process used to discover facts about the world must be describable by the investigator and repeatable by others using the same method of inquiry. At a very basic level, that is how science works. This process presupposes that nature works the same way now as it worked before and the same way that it will work later.

But a collection of facts do not comprise scientific knowledge any more than a pile of feathers makes a duck. Facts, though crucial, are intermediary. Facts must be interpreted. Scientists relate facts to formulate theory. The major usefulness of theories is to make predictions and inferences about nature, what it is and how it works and how it will work.

Ultimately, theories that interpret facts, and that can be used to predict accurately future events within the theoretical scope, come to form the basis of scientific consensus. Example: NASA doesn’t re-investigate the nature of gravity every time it wants to send a rocket into space. There is a scientific consensus about gravity resting on the affirmations of gravitational theory to such a high degree that it is literally pointless to reopen investigations of gravity just to shoot another rocket. True, at the far reach of theoretical physics there is not a consensus about gravity’s nature, but theoretical physicists do not launch rockets. Practical scientists and engineers do. And they are in consensus about gravity insofar as gravity affects their work.

What the media have generally failed to distinguish in their coverage of global warming issues is the difference between the consensus that the earth is warming overall, and the lack of consensus about the causes of the warming, especially the degree of warming attributable to human activities.

Recently, much ink and airtime was given to the latest release by the UN-sponsored Intergovernmental Panel on Climate Change (IPCC). When reporting the IPCC’s latest release the media have generally not only failed to distinguish between the two issues just mentioned, but have also not generally recognized the IPCC for what it is. The IPCC’s own web site (this page) informs us that the IPCC is not a research agency and conducts no research at all. It is chartered to assess,

… the scientific, technical and socio-economic information relevant to understanding the scientific basis of risk of human-induced climate change, its potential impacts and options for adaptation and mitigation. The IPCC does not carry out research nor does it monitor climate related data or other relevant parameters. It bases its assessment mainly on peer reviewed and published scientific/technical literature.

Note carefully that the IPCC’s beginning premise is ” human-induced climate change,” and perusing its documents shows that all conclusions flow from that basic premise. Earlier this month the IPCC released the executive summary of it forthcoming fourth report, which is promised sometime later this year. The summary states that the earth is getting warmer, continuing a warming trend that has been going on, with variability, since 1750, and that the trendline has accelerated since 1950. However, the fourth report’s summary also reduced the amount of warming from that claimed in the third report, issued in 2001. The fourth report’s apparent bottom line: the earth is warming, but not as much as we thought, and warming’s effects will not be a great as we thought before. Even so, of seven identified phenomena and direction of trends (p. 9 of the summary), the report says that the “Likelihood of a human contribution to observed trend[s]” ranges from “more likely than not” to “likely.”

Does this report represent scientific consensus? From my reading, the answer seems to be yes and no. Before explaining why, let’s take another look at what a scientific consensus is.

A simplified model of the scientific method is this. A phenomenon is observed. An explanatory hypothesis about the phenomenon is formed. Empirical tests and measurements are performed to confirm, or not, the hypothesis. Over time enough data are collected to refine the hypothesis into a theory. A theory is a comprehensive explanation of the phenomenon that can also be used to predict future occurrences and the condition in which they would occur. The ability of theory to serve as a predictive model is crucial to science and the nature of a theory itself.

Many non-scientists do not understand the role of theory in science. In non-scientific discourse, saying something is “just a theory” is a way to dismiss it. “Just a theory” in such conversations means unconfirmed, undetermined, speculative and unreliable. But that’s not what theory means to scientists. The major usefulness of theories is to make predictions and inferences about nature, what it is and how it works and how it will work.

A theory, then, is not just a guess. A theory is how scientists express the interpreted results of many observations carried out over a long time. A theory is how scientists make sense of their collective experience. The formulation and reformulation of theory is, I think, grounded in the deep human need to establish meaning. Because we exist in nature, we are compelled at a most fundamental level to explore what nature means. Science is one very powerful and reliable way we do that. Science, and scientifically-based meaning, can no more exist apart from theory than Barry Bonds’ home-run record could exist apart from baseball.

“Just a theory” is an accusation that actually makes no sense. It’s really “just a theory” that gravity holds us on the earth with a force equal to the inverse of the square of our distance from the planet, but does anyone care to jump off the Empire State Building tomorrow because, hey, gravity is “just a theory?” Our understanding of how wings keep airplanes up is just a theoretical understanding, but millions of people per month literally bet their lives that the theory is correct.

Theory is to science as money is to finance. Theory is to science as scales are to music. Theory is to science as yard lines are to football games.

Yet theories are not inherently infallible. They can be overturned. Example: Darwinian evolution was once accepted by evolutionary biologists but has been pretty much abandoned now. Biologists still affirm evolution theory’s ’s basic premise - that species evolved into other species - but argue quite a bit over how it happened and why. Creationists and others who scoff that evolution is “just a theory” conflate scientific dispute over how evolution happened with the consensus that it did happen.

Another example: certainly there is consensus that dinosaurs exist no longer. Yet scientists have not quite come to a consensus about how they perished. The theory of an asteroid strike near present Yucatan 65 million years ago is compelling to scientists, but has not yet reached the status of consensus.

So what is “consensus?” It is when scientists within a particular field of scientific inquiry have reached such a degree of agreement on a question that there is no substantial doubt about the theory relating to the question.

But before consensus can be reached on theory, it must be reached on the theory’s empirical basis. Empirical data are the foundation of science and so all scientists have a deep interest in the validity of empirical evidence and measurement. A lot of the argumentation within science is over the validity of data, the accuracy of measurements and the inclusion of relevant data and measurements within the development of theory.

As far as I can tell, it is accurate to say that there is a scientific consensus that the earth is getting warmer. That the amount of warming predicted for the future has been lowered since 2001 does not obviate the consensus about the trend. But this is really just consensus over the validity of the empirical measurements, which is the easiest kind of consensus to reach.

There is no consensus on why the earth is getting warmer and therefore no consensus on how much the warming is influenced by human activities. The IPCC’s claims that warming trends are “likely” anthropogenic should not be dismissed out of hand, but neither should they be seen as holy writ. After all, to claim that something is “likely” is actually to show there is no consensus! Besides, many highly-credentialed climatologists say not so fast. Thomas Sowell lists some:

There is Dr. S. Fred Singer, who set up the American weather satellite system, and who published some years ago a book titled “Hot Talk, Cold Science.” More recently, he has co-authored another book on the subject, “Unstoppable Global Warming: Every 1500 Years.”

There have been periods of global warming that lasted for centuries — and periods of global cooling that also lasted for centuries. So the issue is not whether the world is warmer now than at some time in the past but how much of that warming is due to human beings and how much can we reduce future warming, even if we drastically reduce our standard of living in the attempt.

Other serious scientists who are not on the global warming bandwagon include a professor of meteorology at MIT, Richard S. Lindzen.

His name was big enough for the National Academy of Sciences to list it among the names of other experts on its 2001 report that was supposed to end the debate by declaring the dangers of global warming proven scientifically.

Professor Lindzen then objected and pointed out that neither he nor any of the other scientists listed ever saw that report before it was published. It was in fact written by government bureaucrats — as was the more recently published summary report of the Intergovernmental Panel on Climate Change (IPCC) that is also touted as the final proof and the end of the discussion.

You want more experts who think otherwise? Try a professor of environmental sciences at the University of Virginia, Patrick J. Michaels, who refers to the much ballyhooed 2001 IPCC summary as having “misstatements and errors” that he calls “egregious.” …

Skeptical experts in other countries around the world include Duncan Wingham, a professor of climate physics at the University College, London, and Nigel Weiss of Cambridge University.

Sowell cites another “professor of climatology at the University of Delaware, David R. Legates,” who points out that the summary of the 2001 IPCC report was “often in direct contrast with the scientific report that accompanies it.” Since the 2007 full report has not been published yet, we’ll have to see how it and its summary mesh. Another non-consensus voice is Dr. Timothy Ball, Canada’s first Ph.D. in climatology, who wrote,

The world has warmed since 1680, the nadir of a cool period called the Little Ice Age (LIA) that has generally continued to the present. These climate changes are well within natural variability and explained quite easily by changes in the sun. But there is nothing unusual going on.

I wrote more about the infuence of the sun’s magnetic field here. Obviously, we cannot control that.

Ah, here enters that word: “control.” For the upshot of all this is that the politics and ideology of global warming have moved far ahead of the science. And the political-ideological impetus is decidedly so slanted that it has no attachment to what scientific consensus there is. More about this later.

Update: One reason there is no consensus on the primary causes of warming is that climate-predicting models are terribly inexact. This is shown by the large changes in predicted future warming between the IPCC’s prior report and this one, and also by developments such as this.

COLUMBUS , Ohio – A new report on climate over the world’s southernmost continent shows that temperatures during the late 20th century did not climb as had been predicted by many global climate models.

This comes soon after the latest report by the Intergovernmental Panel on Climate Change that strongly supports the conclusion that the Earth’s climate as a whole is warming, largely due to human activity.

It also follows a similar finding from last summer by the same research group that showed no increase in precipitation over Antarctica in the last 50 years. Most models predict that both precipitation and temperature will increase over Antarctica with a warming of the planet. …

David Bromwich, professor of professor of atmospheric sciences in the Department of Geography, and researcher with the Byrd Polar Research Center at Ohio State University, reported on this work at the annual meeting of the American Association for the Advancement of Science at San Francisco.

“It’s hard to see a global warming signal from the mainland of Antarctica right now,” he said. “Part of the reason is that there is a lot of variability there. It’s very hard in these polar latitudes to demonstrate a global warming signal. This is in marked contrast to the northern tip of the Antarctic Peninsula that is one of the most rapidly warming parts of the Earth.”

Bromwich says that the problem rises from several complications. The continent is vast, as large as the United States and Mexico combined. Only a small amount of detailed data is available – there are perhaps only 100 weather stations on that continent compared to the thousands spread across the U.S. and Europe . And the records that we have only date back a half-century.

“The best we can say right now is that the climate models are somewhat inconsistent with the evidence that we have for the last 50 years from continental Antarctica .

“We’re looking for a small signal that represents the impact of human activity and it is hard to find it at the moment,” he said.

But we’ll keep looking, you betcha. See also, “Glaciers come, glaciers go.”

No, this was not a campaign mounted by the NRA, but by activists for the homeless at Ohio State University.

In 1993, a press release was given to the Columbus, Ohio, news media that announced the formation of a new charity to help homeless people. They would provide the homeless with protection in the form of guns. They called the organization, “The Arm the Homeless Coalition.”

See how it turned out.