There is a nice, and very short, essay in the Oxford English Reference Dictionary on the philosophical underpinnings of the word skepticism (which the Oxford spells, scepticism -- obviously):
Oxford says: "The ancient doctrine of scepticism (also called Pyrrhonism) was established by Pyrrho and continued at the Academy in Athens. In modern philosphy, scepticism has taken many forms: the most extreme sceptics have doubted whether any knowledge at all of the external world is possible (see solipsism), Descartes attempted to question his own existence, while others asked whether ojbects exist when not experienced (Berkeley's idealism), or whether objects exist at all beyond our experiences of them (Hume)."
This is wonderful fodder for philosophical debate (When an tree-hugger comes out of the forest, is he still wrong?), but positively useless in trying to hash our reasonable policy in a world in the midst of an unprecedented climatic experiment.
Interestingly, Oxford's second definition for solipsism, is "self-centredness, selfishness," which seems to sum up the fossil-fools' position perfectly.