That leaves 19. There are a number of issues with doing any meaningful analysis on this, including:
- There are only 19
- The 19 are not a random sample from the list.
- There are probably gaps where I didn't see an argument used
- They are represented unequally. Some have whole websites full of arguments, some only a single short letter of arguments.
The top 5 arguments used by the 19 entries and the breakdown are:
It's the sun (6) Bob Breck, John L. Casey, Art Horn, Dr. Cal Evans, Mike Thompson, Richard Mourdock
water vapor is the most powerful greenhouse gas (6) Bob Breck, Dr. Martin Hertzberg, Dr. Robert H. Essenhigh, Frank Britton, Art Horn, Dr. Cal Evans
CO2 concentration is small (5) Bob Breck, Dr. Martin Hertzberg, Hans Schreuder, Frank Britton, Dr. Cal Evans
It hasn't warmed since 1998 (5) Bob Breck, Dr. Wilson Flood, Allan M.R. MacRae, Bill Steffen, Joseph Conklin
human co2 is a tiny % of co2 emissions (4) Dr. Robert H. Essenhigh, Frank Britton, Art Horn, Mike ThompsonAs #3 and #4 points out, the reason many of the same names are present is probably due to unequal representation.
A relevant hypothesis I have held for a long time, not based on the above, is that whatever makes a person susceptible to believing one of the worst arguments (I consider the above to be some of the worst), they will be susceptible to all of them.
ie if a person is not skeptical of the "human co2 is a tiny % of co2 emissions" and readily believes it, then they will very likely also be taken in by the "water vapor is the most powerful greenhouse gas" argument. At least I see little reason why a person would believe one and not the other.
So I suspect to see a pattern like the above where a person using one argument will tend to also be using the other.
Skepticalscience directly covers 4 of the 5 above arguments, with "CO2 concentration is small" covered in related topics. It is interesting that the worst arguments are perhaps the most popular, but perhaps this is explained by the simplicity of the arguments and the relatively few people who look into them in any detail.
So a classification system for skeptics will probably contain a large group consisting of people that believe these type of arguments. There are many other skeptics who would distance themselves from such arguments and so would have to placed in different groups.