I've developed a new angle for my list of climate scientists that I believe opens up new insights into the list. I've tracked down ten public declarations or open letters to leaders regarding climate change - six 'skeptical' and four 'activist,' as I'll dub them. The 'activist' letters issue a strong call for prompt action on reducing greenhouse gas emissions. The 'skeptical' letters argue that GHG emission cuts will be economically devastating, and generally go on to question the very basis of the case for such reductions: the existence or strength of a greenhouse forcing effect of rising CO2 concentrations; the attribution of current temperature trends to human emissions; the validity of the historical temperature record itself; the significance of projected harmful impacts of rapid warming or sea level rise; and so on.
I've linked to websites of each of the ten documents. I've downloaded the list of signatories, worked these into tabular form and checked for duplicates. I've given each statement a short tag, which I've entered in the "notes" column beside each author's name who signed the document. I've colour-coded the notes cell in the table to show signers of the activists documents in green, with the 'skeptics' documents in grey. (I also count as activist the ten contributors to the website Realclimate; among the skeptics I also count those interviewed in the TV documentary The Great Global Warming Swindle.)
I've limited this to documents I believe were signed knowingly and where the signers' identities are clear from the document, and are specifically from scientists. This excludes the vast but untraceable list on the so-called "Oregon Petition" (much favoured by Sen. Inhofe) as well the list of skeptics maintained by Sen. Inhofe's staffer Marc Morano, which largely tracks the lists I've cited with various additions gathered by Morano, but has more than a few names of people who objected strongly on learning they had been listed.
A single exception is that (action advocate, Bali declaration supporter) Dr. Carl Wunsch of M.I.T. was included in The Great Global Warming Swindle unaware of the film's editorial stance, and promptly denounced how the film characterized his views and rejected its conclusions.
The colour-coded notes boxes makes it immediately visible how the top scientists are 'voting' on these appeals. Of the top 100 most cited authors in my list as of now, I find some 35 have signed activist appeals, but just two signed skeptics' appeals (plus one other name, Vincent Courtillot, who I recognize is a "climate skeptic" but who has not signed one of the listed statements) 35 to 3, i.e. over eleven to one in favor of activism over 'inactivism.'
The non-signers should not be considered undecided on these questions, just simply ones who did not happen to take part in any of these open letters. I would further argue that the IPCC Assessment Reports are themselves quite strong calls to action, progressively more urgent and unequivocal with each round. None of the 619 authors of AR4 wg1 signed any of the skeptics' open letters I've listed.
However, many skeptics or contrarians like to argue that the "consensus" within the IPCC is somehow tainted by "group think," excessive peer pressure or politicization of the review process (the objection given by Dr. Chris Landsea as leading to his resignation.) Without acceding to any of those portrayals, I've kept the IPCC participation as a separate column which I don't refer to in counting some authors as "activists." So names with a plain white background in the notes column can be seen as "non-signers" who have signed neither an activist nor a skeptical appeal, excluding IPCC reports.
Many IPCC authors fall under the 'non-signer' category, but none have signed any of the skeptics' appeals. Looking at the table of 619 contributing authors to IPCC AR4 wg1, the only names linked to strong 'skeptics' positions are Dr. Landsea, and Dr. John Christy of UAH, who appeared in the film The Great Global Warming Swindle.
Of the 63 'non-signers' among the top 100 most-cited, some 39 were AR4 wg1 contributing authors.
I would argue a large share of the non-signers would be more inclined to agree with the activists and not the skeptics, but that's another debate; it can be approached by looking at their published work, obviously, but that takes both effort and interpretive judgment.)
For now, let my data on the number of signatories of clearly activist or skeptical appeals stand on their own: of the top 500 most-cited authors on climate, 130 have signed appeals for prompt action (outside of the IPCC assessments themselves); twenty-two of the 500 have signed a skeptical statement. At this level, the outspoken activists outnumber the skeptics by six to one, and skeptics make up just 4.4% of authors.
I've added a petitions page with background on the public appeals from scientists, as well as some of the largest petitions on climate change from the general public.