Part 2 here requires a little specialized knowledge, namely that there is a broadly based scientific professional society relevant to climate issues in the US; it is the AGU http://www.agu.org, and they have a class of members who have been recognized for their consistently high quality work (Fellows). The American Meteorological Society, http://www.ametsoc.org, is relevant of course, but is primarily meteorological with only a modest number of oceanographers, glaciologists, hydrologists, ... particularly as compared to the numbers the AGU has. On the other hand, AGU includes space physicists, mineralogists, ... as well, which takes us afield from climate. I'm a member of both societies, so you could call it specialized knowledge to know about them. But these organizations are easy enough to find if you set out looking.
In part 1, we looked a bit at whether the numbers of signers was large. The petition project itself, and even more those who quote it, wants us to believe that there is 'a lot' of scientific opposition. But it turns out that most of the signers are nonscientists, much less scientists in something relevant to climate; worse, the numbers are actually quite small compared to the sizes of the fields they were mass mailing to. Junk mail rate.
For part 2 here, let's look to see whether many of the people in the AGU have signed. We'd want to do a later check whether it was mineralogists vs. atmospheric scientists, but it's a start. Since the AGU has about 50,000 members, I didn't want to try checking the whole list. But AGU fellows are a limited population. Unfortunately, it turns out that the 0.1% I mentioned was how many can be inducted per year. Ouch. There are quite a few more Fellows than I was thinking. Nevertheless, I started checking alphabetically.
Last names beginning with A: 0 of 41 fellows have signed
Last names beginning with B: 0 of 91 fellows have signed
As this is tedious and error prone (just how many 'Browns' are there? yikes. Names like Grumbine are much easier!) I turned to the list of 2008 fellows (not yet included in the full list). There are 51 new members. Checking the names there, I found 2 name matches, but ... Well, the names that matched are Charles R. Bacon and James W. Kirchner. But the Fellow Bacon is working in California and the signer Bacon is in Michigan, while the Fellow Kirchner has a PhD and the signer does not. So we're to 0 of the 51 new Fellows. (I'll note that it isn't a requirement that a Fellow, or AGU member, have a PhD. What matters is doing good work in the area (Fellow) or be studying or have studied the area (member).)
0 of the 183 AGU Fellows I've checked so far have signed the petition. If you'd like to assist the check, please do; send your results to me at plutarchspam at aim dt com. AGU's listing of fellows is at http://www.agu.org/inside/fellows.html The Petition Project's listing of signers is at http://petitionproject.org/gwdatabase/Signers_By_Last_Name.php And, by all means, do recheck my tallies for what I've checked so far.
The real point, though, is that the petition project has tried to mislead us, not the exact numbers. They want us to believe that engineers, doctors, and veterinarians (among other things) are scientists; they're not. They want us to believe that the number of signers is not 'a few', but as I've shown in parts 1 and 2, using only information that requires no special study, it in fact is only a few -- under 1% of the people they consider eligible have signed (in the areas I've checked, to be sure, but I did hit the largest groups). They want us to believe that the petition is about science, but the petition itself doesn't ask any scientific questions (check it out, pay attention to that major weasel word 'catastrophic'), and its main conclusion is actually about signing political agreements -- not science. And ... well, quite a few things, including that being dead is no bar to being on the list. Edward Teller, signer of their sample form, has been dead since 2003.
What should a citizen do when trying to figure out where the science is on climate change? It'd take forever to go through every document on every site and read every book and then apply this sort of method to it. My take is that sources which mislead me on basic things that I can check probably don't suddenly get more accurate in the areas that I can't. If it's a major project of the organization (as opposed to some loose cannon shot off his mouth), then that organization (or that loose cannon) is an unreliable source. This project is a major effort (later spun off to its own project and web domain ) of the http://www.oism.org/, and several of its staff (of 6 faculty and 7 regular volunteers) are the major people involved in the petition project. Your call as to loose cannon vs. institution, but it's several loose cannons from a small group.
That weeds out a couple of web sites and a few people as dubious sources, which doesn't really gain us a lot in a world with millions (billions?) of web sites and billions of web pages.
But we can go another step and consider folks who cite the petition project as showing what the project claimed. As I've shown, it doesn't take much research to find that the project's claims don't match what is really there. So, people and sources that cite it uncritically are at least not doing homework on what they cite to me. I do mention a number of things in chatting with a friend over a beer that I've never researched (life being short already) but that I just heard somewhere. Fine. But it does mean that in those areas I'd be a poor person to try to learn the topic from. Not that I (or those petition-citing sources) are bad folks, but we haven't done homework in those areas. Doing a web search on '31,000 scientists' brings up a ton of hits (something like 40,000). On the first two pages citing the petition uncritically (or even enthusiastically) are:
Cites as an 'exclusive', not an editorial. Bob Unruh
blog, Noel Sheppard.
As best I can see, none are editorials or opinion when at news outlets.
I'll start a summary of unreliable sources, probably at my web site rather than here. Please do suggest other candidates, to the same address. To be a candidate, the site or person must: make an error that can be detected by a nonspecialist -- on an important point to his argument (a primary dubious source), or, cite a primary dubious source uncritically. Not all errors count; for example, in my first paper a word was supposed to be 'parameter', but it got published with 'satellite'. An error, but it didn't affect the argument about ice sheets. For now, it also doesn't count that one person using highly specialized methods detected an error in another highly skilled person's work. I'm going for that citizen level where people can throughly check things out for themselves. That's why, for instance, I have so many links here and the notes are excruciatingly long. Check everything out yourself. If you think I'm wrong, send me your reasons why, with at least equal care to what I've done.