Why aren't more philosophers involved in discussions and policy on global warming? It is a desperate issue to be addressed and regardless of the philosophical stance in regard to it (i.e. moral skepticism), moral reasons and moral knowledge motivate action in a profound way! I do not think that much progress can be made towards addressing global warming unless the moral seriousness of the matter becomes clear to people and our unjustified indifference is slashed. The culture and spirit of the time should inspire philosophy, just as the excessive violence inspired Descartes in his skeptical exploits. If philosophers, whose reason is supposed to be strong to say the least don't get very involved, who should? I'm sure that this is a bit outlandish, but under what current conditions does a philosopher not have an obligation to get involved? Also, this would be a nice way to reconnect philosophy to the world, especially since a lot of its progress is connected to the insights of philosophy and reason.
I don't know about other philosophers, but their reluctance may be motivated by thoughts such as those Gerald Gaus expresses in his essay "Should Philosophers Apply Ethics?" in Think (2005), pp. 63-67, available at http://journals.cambridge.org/action/displayJournal?jid=THI&tab=mostdownloaded I am involved in a new organization called ASAP -- Academics Stand Against Poverty -- which (in a soon-to-be-posted essay) has examined and argued against Gaus's arguments and is now very actively doing the kinds of things that Gaus warns against. You can find some relevant material on our website www.academicsstand.org . You will there also find that one of our current projects is "Climate Voices", a project that focuses on global warming and its effects on people whose home environment is made uninhabitable thereby. This project is, by the way, essentially run by students.