I guess the truth of the matter is that I came to think of myself as a skeptic by way of an accident.
I was working on the manuscript for my book, in which I critique the speculative pretentions of the conventional approach to environmental ethics. Since I consider myself an environmental philosopher, I wanted the title of the manuscript to convey that I am an environmentalist who entertains some serious doubts about a particular way of arguing for environmentalists' values rather than some kind of rabid anti-environmentalist.
"Skeptical Environmentalism" seemed to fit the bill.
So, I read a bit about skepticism, settling on David Hume's "moderate" or "mitigated" skepticism as a useful starting-point, and left it at that.
(The fact that Bjorn Lomborg published his Skeptical Environmentalist just a few months before my book came out is a coincidence, with some interesting repercussions on the sales of my book - and on the number of used copies that are currently available on the market. I've written about Lomborg for publication, but suffice it to say that I have very little in common with him, since he isn't even close to being a genuine skeptic. With him, it's "doubt for thee, but not for me.")
It turns out that the label, "skeptic", fits me fairly well, given my firmly-ingrained suspicion of all dogma. Recently, I've revisted the idea of skeptical environmentalism, burrowing into the philosophical tradition to clarify what skepticism means. I read Sextus Empiricus for the first time, and studied Hume in much greater depth.
(I seem to have a thing for the eighteenth century: a few years ago, I was obsessed with Rousseau, more recently Hume, and still more recently Kant. Long before any of this, I went to France in order to study the 18th-century roots of modern ecology, starting with the naturalist Buffon.)
The more I read, the more skepticism appeals to me as a philosophical method, a general attitude, perhaps even a way of life. For me, it fits together with a general sort of humanist outlook and a commitment to participatory democracy. (We're all in this together, we don't know much, and we have to figure out how to go on from here. If we don't hang together . . .)