I have seen a number of these ad homonym attacks over the last few days and they are disgusting. It does seem to be a method of operation for the far left, to attack scientists, or anybody who disagrees, based on a variety of totally irrelevant issues. I have noticed however an extreme reliance by some in here on the opinions of others, especially large governmental agencies and quasi governmental agencies, without much critical analysis. Maybe it is unique to my particular discipline, but we are taught to question all conclusions and recommendations in light of the data (in its purest possible form). I have seen tons of peer reviewed articles and research that present wonderful data, which in no conceivable way supports the conclusions and recommendations.
Statements from various geological societies must be taken with a large grain of salt. Most statements issued are done so in order to bolster that society's position at the governmental table and is unrelated to AGW in any way!
The AGU has about 50,000 members (mostly astrophysicists or theoretical geophysicists) and the GSA has about 22,000 members. I used to belong to GSA but the membership had very little use to me and was a place where the "hard rockers" and tended to hang out. I was trained as one and I understand the need for those societies. They have excellent publications.
The combined SEG and CSEG have about 31,300 members who are mostly theoretical and applied geophysicists who are interested in applications and case studies. The combined AAPG and CSPG have about 32,300 members and are the largest body of applied and research geologists on the planet.
I can assure you that again, all of the discussion in the latter societies is in relation to a political position, not a scientific one. The vast majority of the membership, from what I read in the op-ed pieces or the Letters, are opposed to the concept of AGW and present very sound arguments in that direction. Maybe 1% of Letters support any significant role of anthropogenic causes!
None of the 3 Societies to which I belong, have even suggested a unified position or the aggregation of scientific literature for review on the subject. If that doesn't tell you that the issues are political as opposed to scientific, nothing will!
EDIT: The comments on the participation of membership in the various Societies, Associations and Licensing bodies by several posters indicates to me that they probably do not belong to any such organizations. If they did, they would understand the process of appointments and elections in such bodies and realize that apathy is a far more considerable force in these elections than is democracy or the will of the membership. The most "favourable" opinion of AGW comes from the licencing body to which I belong, which has a whopping 20% participation rate! Sad but true!