What can a philosopher say about global warming? The first thing he can and ought to say is that, although not all questions are empirical, at the heart of the global warming debate are a set of empirical questions. These are not questions for philosophers qua philosophers, let alone for political ideologues. For the resolution of these questions we must turn to reputable climatologists whose roster does not sport such names as 'Al Gore,' 'Barbra Streisand,' or 'Ann Coulter.' Unfortunately, the global warming question is one that is readily 'ideologized' and the ideological gas bags of both the Right and the Left have a lot to answer for in this regard.
I have not investigated the matter with any thoroughness, and I have no firm opinion. It is difficult to form an opinion because it is difficult to know whom to trust: reputable scientists have their ideological biases too, and if they work in universities, the leftish climate in these hotbeds of political correctness is some reason to be skeptical of anything they say. For example, let's say scientist X teaches at Cal Berkeley and is a registered Democrat. One would have some reason to question his credibility. He may well tilt toward socialism and away from capitalism and be tempted to beat down capitalism with the cudgel of global warming. Equally, a climatologist on the payroll of the American Enterprise Institute would be suspect. I am not suggesting that objectivity is impossible to attain; I am making the simple point that it is difficult to attain and that scientists have worldview biases like everyone else. And like everyone else. they are swayed by such less-than-noble motives as the desire to advance their careers and be accepted by their peers. And who funds global warming research? What are their biases? And who gets the grants?
Off the top of my head I think we ought to distinguish among the following questions:
1. Is global warming (GW) occurring?
2. If yes to (1), is it naturally irreversible, or is it likely to reverse itself on its own?
3. If GW is occurring, and will not reverse itself on its own, to what extent is it anthropogenic, i.e., caused by human activity? This is the crucial empirical question. It is obviously distinct from (1) and (2). If there is naturally irreversible global warming, this is not to say that it is caused by human activity. It may or may not be. One has to be aware of the post hoc ergo propter hoc fallacy. Suppose there is a close correlation between global warming and man-made carbon emissions. It doesn't straightaway follow that the the human activity causes the warming. But again, this is not a question that can be settled a priori; it is a question for climatologists.
4. If anthropogenic, is global warming caused by humans to a degree that warrants action, assuming that action can be taken to stop it?
5. If GW is caused by humans to an extent that it warrants action, what sorts of action would be needed to stop the warming process?
6. How much curtailment of economic growth would we be willing to accept to stop global warming?
The first three of these six questions are empirical and reserved for climatologists. But the last three are not, being questions of public policy. So although the core issues are empirical, philosophers have some role to play: they can help in the formulation and clarification of the various questions; they can help with the normative questions that arise in conjunction with (4)-(5), and they can examine the cogency of the arguments given on either side. Last but not least, they can drive home the importance of being clear about the distinction between empirical and conceptual questions.