As promised, I've started to investigate the claims and counter-claims surrounding global warming. First, I lay out my biases:
Give my biases, it probably comes as no surprise that the information sources I've found most trustworthy on the Internet are global warming skeptics: the likes of World Climate Report, CO2 Science, Prometheus, and Roy Spencer.
It does appear that the earth is warming. (In fact the earth has been warming generally since the end of the last ice age.) The best estimates I've found on the Net indicate that the earth's temperature over the last 30 years has increased at a steady (not exponentially increasing) pace of about 0.17° C every 10 years. So far I've found no evidence that "human interference with the natural order" is the only or even primary cause of this relatively low level of warming (that would be 1.7° C over 100 years, far from the Chicken-Little scenarios of 5.8° C and up). Furthermore, the climate system is so complex that we really don't understand it yet. Existing climate models are not only incomplete, but they are just that: models. We don't have reliable temperature records for most of the earth except over the last 30+ years (since we started launching satellites) and even modern temperature recording emerged only in the 1850s, and then only at the surface and mostly in developed regions. Anything before 1850 is pure guesswork based on tree ring sizes and the like, not hard data. Green activists and climate researchers whose livelihood depends on continued funding like to point to carbon dioxide and methane emissions as the smoking gun, but there was smoke (warming) before the gun was invented (cf. the Middle Warm Period, not to mention earlier episodes of warm climates, when even northern climes like Wyoming and Alberta were tropical). Both carbon dioxide and methane are produced in copious amounts by plant life such as the tropical rain forests, and are not caused exclusively or even primarily by "human intereference" (we just don't know enough yet to say). Even a doubling of carbon dioxide in the atmosphere would by itself result in planet-wide warming of less than 2° C; forecasts of greater increases depend on assumptions about various forcing factors (cloud formation, water vapor, ice cap meltoffs, etc.) that are very far from understood. And even a 2° C increase in global temperatures would not result in catastrophe: humans would adjust quite easily, the polar ice caps would not melt, runaway "greenhouse" effects (Earth turning into Venus) would not ensue, etc.
As far as I can see, we need to invest in new and improved mass-market energy technologies (not just a few wind farms here and there, but in all likelihood modern nuclear power generation methods), work to develop technologies (such as nanotech) that would result in seriously reduced energy usage, and get as many economies as possible past the crucial $3000 yearly income level (which is when people start devoting productive potential to industrial hygiene and cleaner methods of production). We also need to invest in continuing efforts to understand the climate system, including the role of inputs from the only power source external to the system: the sun. For instance, there seem to be 210-year and 86-year solar cycles involved, which lead to 1470-year climate cycles (and the earth has generally been warming up for most of the last 1470 years -- at least since 800 A.D. if the tree rings are to be believed).
So to my mind the jury is still out on the severity of global warming and, more importantly, on its causes. More to follow as I do more reading...