By David Deming

I'm a denier for several reasons. There is no substantive evidence that the planet has warmed significantly or that any significant warming will occur in the future. If any warming does occur, it likely will be concentrated at higher latitudes and therefore be beneficial. Climate research has largely degenerated into pathological science, and the coverage of global warming in the media is tendentious to the point of being fraudulent. Anyone who is an honest and competent scientist must be a denier.

Have you ever considered how difficult it is to take the temperature of the planet Earth? What temperature will you measure? The air? The surface of the Earth absorbs more than twice as much incident heat from the Sun than the air. But if you measure the temperature of the surface, what surface are you going to measure? The solid Earth or the oceans? There is twice as much water as land on Earth. If you decide to measure water temperature, at what depth will you take the measurements? How will the time scale on which the deep ocean mixes with the shallow affect your measurements? And how, pray tell, will you determine what the average water temperature was for the South Pacific Ocean a hundred years ago? How will you combine air, land, and sea temperature measurements? Even if you use only meteorological measurements of air temperature, how will you compensate for changes in latitude, elevation, and land use?

Determining a mean planetary temperature is not straightforward, but an extremely complicated problem. Even the best data are suspect. Anthony Watts and his colleagues have surveyed 82.5 percent of stations in the U.S. Historical Climatology Network.They have found -- shockingly -- that over 70 percent of these stations are likely to be contaminated by errors greater than 2 deg C [3.6 deg F]. Of the remaining stations, 21.5 percent have inherent errors greater than 1 deg C. The alleged degree of global warming over the past 150 years is less than 1 deg C. Yet even in a technologically advanced country like the US, the inherent error in over 90 percent of the surveyed meteorological stations is greater than the putative signal. And these errors are not random, but systematically reflect a warming bias related to urbanization. Watts has documented countless instances of air temperature sensors located next to air conditioning vents or in the middle of asphalt parking lots. A typical scenario is that a temperature sensor that was in the middle of a pasture a hundred years ago is now surrounded by a concrete jungle. Urbanization has been a unidirectional process. It is entirely plausible -- even likely -- that all of the temperature rise that has been inferred from the data is an artifact that reflects the growth of urban heat islands.

The "denier" is portrayed as a person who refuses to accept the plain evidence of his senses. But in fact it is the alarmist who doesn't know what they are talking about. The temperature of the Earth and how it has varied over the past 150 years is poorly constrained. The person who thinks otherwise does so largely because they have no comprehension of the science. Most of these people have never done science or thought about the inherent difficulties and uncertainties involved.

And what is "global warming" anyway?

As long ago as the fifth century BC, Socrates pointed out that intelligible definitions are a necessary precursor to meaningful discussions. The definition of the term "global warming" shifts with the context of the discussion. If you deny global warming, then you have denied the existence of the greenhouse effect, a reproducible phenomenon that can be studied analytically in the laboratory. But if you oppose political action, then global warming metamorphoses into a nightmarish and speculative planetary catastrophe. Coastal cities sink beneath a rising sea, species suffer from wholesale extinctions, and green pastures are turned into deserts of choking hot sand.

In fact, so-called "deniers" are not "deniers" but skeptics. Skeptics do not deny the existence of the greenhouse effect. Holding all other factors constant, the mean planetary air temperature ought to rise as the atmosphere accumulates more anthropogenic CO2. Christopher Monckton recently reviewed the pertinent science and concluded that a doubling of CO2 should result in a temperature increase of about 1 deg C. If this temperature increase mirrors those in the geologic past, most of it will occur at high latitudes. These areas will become more habitable for man, plants, and other animals. Biodiversity will increase. Growing seasons will lengthen. Why is this a bad thing?

Any temperature increase over 1 deg C for a doubling of CO2 must come from a positive feedback from water vapor. Water vapor is the dominant greenhouse gas in Earth's atmosphere, and warm air holds more water than cold air. The theory is that an increased concentration of water vapor in the atmosphere will lead to a positive feedback that amplifies the warming from CO2 by as much as a factor of three to five. But this is nothing more that speculation. Water vapor also leads to cloud formation. Clouds have a cooling effect. At the current time, no one knows if the feedback from water vapor will be positive or negative.

Global warming predictions cannot be tested with mathematical models. It is impossible to validate computer models of complex natural systems. The only way to corroborate such models is to compare model predictions with what will happen in a hundred years. And one such result by itself won't be significant because of the possible compounding effects of other variables in the climate system. The experiment will have to repeated over several one-hundred year cycles. In other words, the theory of catastrophic global warming cannot be tested or empirically corroborated in a human time frame.

It is hardly conclusive to argue that models are correct because they have reproduced past temperatures. I'm sure they have. General circulation models have so many degrees of freedom that it is possible to endlessly tweak them until the desired result is obtained. Hindsight is always 20-20. This tells us exactly nothing about a model's ability to accurately predict what will happen in the future.

The entire field of climate science and its coverage in the media is tendentious to the point of being outright fraudulent. Why is it that every media report on CO2 -- an invisible gas -- is invariably accompanied by a photograph of a smokestack emitting particulate matter? Even the cover of Al Gore's movie, An Inconvenient Truth, shows a smokestack. Could it be that its difficult to get people worked up about an invisible, odorless gas that is an integral component of the photosynthetic cycle? A gas that is essential to most animal and plant life on Earth? A gas that is emitted by their own bodies through respiration? So you have to deliberately mislead people by showing pictures of smoke to them. Showing one thing when you're talking about another is fraud. If the case for global warming alarmism is so settled, so conclusive, so irrefutable...why is it necessary to repeatedly resort to fraud?

A few years ago it was widely reported that the increased concentration of carbon dioxide in the atmosphere would cause poison ivy to grow faster. But of course carbon dioxide causes almost all plants to grow faster. And nearly all of these plants have beneficial human uses. Carbon dioxide fertilizes hundreds or thousands of human food sources. More CO2 means trees grow faster. So carbon dioxide promotes reforestation and biodiversity. Its good for the environment. But none of this was reported. Instead, the media only reported that global warming makes poison ivy grow faster. And this is but one example of hundreds or thousands of such misleading reports. If sea ice in the Arctic diminishes, it is cited as irrefutable proof of global warming. But if sea ice in the Antarctic increases, it is ignored. Even cold weather events are commonly invoked as evidence for global warming. People living in the future will look back and wonder how we could have been so delusional.

For the past few years I have remained silent concerning the Climategate emails. But what they revealed is what many of us already knew was going on: global warming research has largely degenerated into what is known as pathological science, a "process of wishful data interpretation." When I testified before the US Senate in 2006, I stated that a major climate researcher told me in 1995 that "we have to get rid of the Medieval Warm Period." The existence and global nature of the Medieval Warm Period had been substantiated by literally hundreds of research articles published over decades. But it had to be erased from history for ideological reasons. A few years later the infamous "hockey stick" appeared. The "hockey stick" was a revisionist attempt to rewrite the temperature history of the last thousand years. It has been discredited as being deeply flawed.

In one Climategate email, a supposed climate scientist admitted to "hiding the decline." In other words, hiding data that tended to disprove his ideological agenda. Another email described how alarmists would try to keep critical manuscripts from being published in the peer-reviewed scientific literature. One of them wrote, we'll "keep them out somehow -- even if we have to redefine what the peer-review literature is!" Gee. If the climate science that validates global warming is so unequivocal, why is it necessary to work behind the scenes to suppress dissent? You "doth protest too much."

As described in my book, Science and Technology in World History: The Ancient World and Classical Civilization, systematic science began with the invocation of naturalism by Greek philosophers and Hippocratic physicians c. 600-400 BC. But the critical attitude adopted by the Greeks was as important as naturalism. Students were not only allowed to criticize their teachers, but were encouraged to do so. From its beginnings in Greek natural philosophy, science has been an idealistic and dispassionate search for truth. As Plato explained, anyone who could point out a mistake "shall carry off the palm, not as an enemy, but as a friend." This is one reason that scientists enjoy so much respect. The public assumes that a scientist's pursuit of truth is unencumbered by political agendas.

But science does not come easy to men. "Science," George Sarton reminded us, "is a joykiller." The proper conduct of science requires a high degree of intellectual discipline and rigor. Scientists are supposed to use multiple working hypotheses and sort through these by the processes of corroboration and falsification. The most valuable evidence is that which tends to falsify or disprove a theory. A scientist, by the very definition of his activity, must be skeptical. A scientist engaged in a dispassionate search for truth elevates the critical -- he does not suppress it. Knowledge begins with skepticism and ends with conceit.

Finally, I'm happy to be known as a "denier" because the label of "denier" says nothing about me, but everything about the person making the charge. Scientific theories are never denied or believed, they are only corroborated or falsified. Scientific knowledge, by its very nature, is provisional and subject to revision. The provisional nature of scientific knowledge is a necessary consequence of the epistemological basis of science. Science is based on observation. We never have all the data. As our body of data grows, our theories and ideas must necessarily evolve. Anyone who thinks scientific knowledge is final and complete must necessarily endorse as a corollary the absurd proposition that the process of history has stopped.

A scientific theory cannot be "denied." Only a belief can be denied. The person who uses the word "denier" thus reveals that they hold global warming as a belief, not a scientific theory. Beliefs are the basis of revealed religion. Revelations cannot be corroborated or studied in the laboratory, so religions are based on dogmatic beliefs conservatively held. Religions tend to be closed systems of belief that reject criticism. But the sciences are open systems of knowledge that welcome criticism. I'm a scientist, and therefore I must happily confess to being a denier.

David Deming is a geophysicist and associate professor of arts and sciences at the University of Oklahoma. His book, Black & White: Politically Incorrect Essays on Politics, Culture, Science, Religion, Energy and Environment, is available for purchase on Amazon.com.