Considering how heated exchanges can be about science subjects, especially in the context of the environment and global warming, it’s necessary that I define how I use words. For the following list of words there is a definition available on how they are used on this website:

1. Sceptic
2. So-called sceptic
3. Science denier
4. Climate science denier

As needed new terminology will be added to this list.

Sceptic

The word sceptic on this website isn’t used to denote someone who is sceptical of an idea or a majority view. Sceptic as used on this website is a reference to scientific scepticism which is:

A scientific (or empirical) skeptic is one who questions beliefs on the basis of scientific understanding. Most scientists, being scientific skeptics, test the reliability of certain kinds of claims by subjecting them to a systematic investigation using some form of the scientific method. As a result, a number of claims are considered “pseudoscience” if they are found to improperly apply or ignore the fundamental aspects of the scientific method. Scientific skepticism may discard beliefs pertaining to things outside perceivable observation and thus outside the realm of systematic, empirical falsifiability/testability.

This means that a sceptic doesn’t only judge the positions of others based on scientific merit, but also does so for his own positions.

So-called sceptic

Being sceptical about a claim or position doesn’t necessarily make you a sceptic. Scepticism is about checking if claims are supported by evidence (see “sceptic”). This isn’t only about looking at the claims of others, it also includes examining your own viewpoints, the positions you hold, the claims you make, and the quality of the evidence you use for those.

That’s why I often use the word so-called sceptics (others use pseudosceptics). It distinguishes those that are applying sceptical thinking from those that aren’t. At the same time it also doesn’t unfairly paint anyone who might simply be misinformed, misled or is uninformed. It allows someone who isn’t aware of how well the science is established to ask questions and participate without them unfairly being labelled as a science denier or climate science denier.

Science denier

A science denier is someone who outright rejects or denies the existence of a well established scientific theory, fact, research or scientific observation by means of flat-out denial, pseudoscience or apparent dishonesty (or some combination). Examples of these are creationists that reject the theory of evolution, HIV deniers or antivaxxers.

Climate science denier

Anthropogenic global warming is a theory that is based on the following scientific findings:

1. The large rise of CO₂ concentration post 1850 is primarily caused (>80%) by human factors (industrial emissions and land use changes);
2. The statistically significant increase in global temperature in the late twentieth century is primarily caused (>50%) by the enhanced greenhouse effect by the increase in CO₂ and other associated anthropogenic produced increases in gas concentrations;
3. Ongoing increases of those greenhouse gas concentrations will result in increases in global mean surface temperature to levels which will result in severe negative consequences in the near future.

Disagreeing with one or more of these three statements is necessary to make someone a science denier or so-called sceptic, but in itself isn’t sufficient to earn the label of climate science denier. As the denial of the theory of anthropogenic global warming is primarily non-scientific in it’s origins and intentions. Thus, a person is a climate science denier only if they:

1. Hold anthropogenic global warming, as defined above, sufficiently dubious to be incapable of being the basis of policy action;
2. And they support their position on anthropogenic global warming (in their own thinking or public debate) either by:
   1. Flat-out denial (meaning the simple assertion that one or more of the three parts of anthropogenic global warming is false or dubious without supporting it with evidence);
   2. Or pseudoscience (meaning they treat the evidence in a manner indistinguishable from that of pseudoscience);
   3. Or out right dishonesty (meaning their description of the evidence so departs from what can reasonably be supported by said evidence that their statements are indistinguishable from deliberate untruths).

As the three terms 2a, 2b and 2c are disjunct, it is sufficient for any of the three to be true for the person to be a climate science denier, provided term 1 is also true for them.

Part 2 of the definition is a general feature of science denial in general, with suitable alterations of part 1 defining the nature of the denial. For example evolution deniers reject common ancestry and evolution through random mutation and natural selection by means of flat-out denial, pseudoscience or apparent dishonesty (or some combination thereof).

Above definition is based on a comment made by Tom Curtis.