There's a very important difference between healthy, open-minded skepticism and closed-minded skepticism (aka climate denial).
Open-minded skepticism is not only healthy, it is essential to scientific inquiry. Some have gone so far as to define science as "organized skepticism."
We try to maintain a stance of open-minded skepticism, which simply means being open to new ideas but insisting upon seeing the evidence – all the evidence – before drawing a conclusion. It also means constantly reflecting -- and asking others to point out -- any potential biases that may cause us to filter information. All of us, like it or not, gaze out at the world through a mental "lens" distorted by our preconceptions.
Dr. Michael Mann perhaps put it best: "One-sided skepticism is no skepticism at all."
At CB, we prefer the term "closed-minded skeptic," but when this long phrase is just too cumbersome; so we will indicate a so-called skeptic -- who really is just skeptical of one side -- by putting it in quotation marks: "skeptic."
Some skeptics strenulously object to being labeled "deniers." They consider it insulting and associated with "Holocaust deniers," which is in turn associated with anti-semitism. (Obviously, there is nothing anti-semitic about climate change denial and we know of nobody who has ever hinted at that absurdity.) So we try to avoid that term, and in general rather than apply labels of any kind, refer to the cognitive processes of (healthy) skepticism vs. (unhealthy) denial.
In science, "skeptic" is a term of respect, and scientists love to argue. Go to any seminar or conference and you'll see scientists challenging and questionning the others premises.
Regarding climate change, prior to 1960, most scientists were highly skeptical about the anthropogenic global warming hypothesis. It went against the traditional view that climate is self-regulating , it eemed far-fetched -- science is inherently conservative about adopting new ideas -- and most felt there just wasn't enough evidence yet to support it.
But gradually, the evidence accumulated – from hundreds, then thousands of independent studies, from totally different angles. The preponderance of evidence supported the AGW hypothesis, and failed to support alternative hypotheses.
Of course, the best scientists continue to maintain a healthy skepticism about whatever data and hypotheses they are working with, looking for aspects that are puzzling or poorly understood. Working at the edge of what is known, they keep looking new shreds of evidence that can help refine, revise or reject their prevailing view.
In constrast, denial – or "closed-minded skepticism" -- is a universal but unhealthy human tendency. It means forming a conclusion first – for ideological, psychological or financial reasons -- then rejecting evidence that contradicts our pre-formed conclusion. It's a way we fool ourselves and others so we can feel better or avoid change.
Freud explained denial as a psychological defense mechanism against information that makes us uncomfortable. It's a normal human tendency. We all do it sometimes, not only on policy questions but personal matters such as weight, habits or health.
Unfortunately, denying evidence – whether addiction, a straying spouse, or a health symptom -- allows the problem to fester and worsen. Moveover, maintaining the denial, in the face of growing evidence, wastes a lot of energy that could be better spent tackling the problem. It's no accident that much of the research on denial comes from studies of addiction.
Unfortunately, changing one's view, even when faced with mounting evidence, is hard for anybody. It can be embarrassing; it always takes a lot of self-confidence and courage to "Maybe I was wrong."
Sometimes even good, skeptical scientists sometimes get wedded to a position, and slip into denial of evidence. They start out with a healthy questioning attitude, but become invested in a certain point of view and then find it hard – psychologically, or perhaps for fear of "losing face" – to revise their position when faced with new evidence, so they fall into denial. There are many examples of once-distinguished, often older, scientists refusing to accept new ideas and taking their old ideas "to the grave" with them.
That's what economist Paul Samuelson meant when he remarked, "Funeral by funeral, theory advances"