I recently corresponded with a colleague who has acquired a degree of "skepticism" regarding global warming. I've noticed a number of recent posts on DailyKos that seemed to be heading in this direction as well. As with all such discussions the first problem seemed to be one of epistemology - how we know those things that we think we know to be true. Since it's impossible to investigate every claim for yourself, people depend on others who they trust - now we all know here that we can't trust a thing on Fox News, but tracking down trustworthy sources on science can be tricky with the vast amount of disinformation out there on the intertubes. Below I've collected some links that I believe are either worthy of considerable trust in themselves, or provide some indication of trustworthiness of others.
On the simple question of the number of smart people on one side or the other of the "debate", there are certainly a small number of distinguished "skeptics", but they are pretty lonely on their side near the top of this list of most-cited scientists who have commented in some way on climate issues.
The only declared "skeptics" in the top 100 of this list (which changes slightly as names are added or updated) are Freeman Dyson (#51), Richard Lindzen (#78), William Happer (#94), and Antonio Zichichi (#100). Of those four, only 1 (Lindzen) actually has done any research or had previous expertise in climate science or a closely related subject. Meanwhile I counted 36 "activists" in the top 100 (who have signed petitions calling for action on global warming), plus (with some overlap) 33 IPCC authors. More from the analysis there:
* none of the 619 contributing authors to AR4 wg1 have signed any of the five public declarations of 'skepticism;'
* 157 of the 619 have signed one of the four 'activist' statements I've identified;
* just one of the 619, Dr. Christopher Landsea, has resigned over differences on the treatment of hurricane risks;
* of the sixteen people interviewed in Martin Durkin's climate skeptic film The Great Global Warming Swindle only John Christy was on AR4 wg1 (and there are real problems with how Durkin interpreted and presented the views of those interviewed.)
* of the top 500 most cited authors in the larger list, just 23 (4.6%) have signed any climate skeptic declaration, while 184 (37%) -- nearly ten times as many -- have signed an 'activist' statement (aside from the IPCC reports themselves.) [Note: these stats may vary slightly as I update the list with new names and stats.]
More important than the people is the science itself. Ray Pierrehumbert has an excellent (draft) online textbook on the subject which goes through a nice spiral of complexity in describing the atmospheric greenhouse effect, getting into the behavior of real gases, water vapor feedback effects, etc.
Another reference I have found extremely useful is Spencer Weart's history of the subject, "The Discovery of Global Warming" - one thing you learn by reading that is the comprehensive collection of objections and challenges to the science that have been posed over the years.
What is discouraging is seeing these same objections raised again and again, without those raising them seeming to be aware of the history and how these have been answered perfectly adequately decades ago. One site that I've found helpful in addressing recent instances of repeats of old arguments is Skeptical Science.
Of course the primary source on the state of the science has to be the IPCC reports, in particular the background science covered by IPCC Working Group 1. The 4th assessment report, IPCC AR4 WG1 can be found here:
http://ipcc-wg1.ucar.edu/...
I had a lot of questions about modeling, and found chapter 8 (Climate Models and their Evaluation) particularly helpful. Take a look at chapter 6 (Paleoclimate) if you have questions about ice ages and past climate, chapter 9 (Understanding and Attributing Climate Change) on the evidence that we're already seeing the predicted changes, or chapter 10 to understand what's predicted for the future... The summaries are pretty good too, but the meat of the information (and all the links to primary source material) is in the actual scientific chapters.
These are sources I trust, backed by the work of thousands of scientific experts, and by the fact that every substantive claim against them that I've investigated has proven wrong. Every source will have an occasional mistake or error of some sort, but by and large these relate the science in a coherent fashion with manifold links to the basic underlying science of physics, chemistry and biology. If you have doubts, that's fine, but before you pontificate on the subject, try a little humility - educate yourself by reading and trying to understand the depth of analysis that's already gone into the science, and you can learn for yourself who you can trust.