In climate ethics, one could use some of the newer anthologies such as Climate Ethics, ed. by Gardiner, Caney, Jamieson, and Shue (Oxford 2010) or The Ethics of Global Climate Change edited by Arnold (Cambridge 2011). This could be supplemented with introductions such as Northcott's A Moral Climate: the Ethics of Global Warming (Orbis 2009) or Garvey's pioneering The Ethics of Climate Change: Right and Wrong in a Warming World (Continuum 2008).
On a more advanced level, say for a graduate seminar, one could use Gardiner's monograph A Perfect Moral Storm: the Ethical Tragedy of Climate Change (2011). On a more basic level, his edited Climate Ethics (2010) works nicely because of its clear topical structure. An overview (a reprint of the excellent 2004 Ethics paper) is followed by several texts laying out "the nature of the problem," (with an excerpt from the Stern Report, among others), a set of papers on "global justice and future generations" (with classics by Parfit et al.), a set of papers on "policy responses to climate change" (with essays by Singer et al.), and a concluding pair of essays on "individual responsibility". This last part, which is a bit thin, could be paired the superb chapter on "responsibility" in Garvey (2008), and voilà, there's your course on climate ethics.
But climate philosophy is more complex. Its inquiry is not primarily ethical; instead it has a collective-existential orientation, comparing different cultural responses to the ecocrisis. Instead of the straightforward legalistic-analytic approach in climate ethics, its methodology is critical, by engaging with the structural economic drivers of the overshoot (which are never questioned in analytic climate ethics). Its methodology is also synthetic (instead of merely analytic), by engaging with the systems-dimension of sustainability, which, to my mind, is an environmental game changer.
So I'd suggest the following sequence of topics for a seminar on climate philosophy: (1) introductory overview of sustainability science & climatology; (2) milestones in environmental ethics: the land ethic, ecofeminism, and deep ecology; (3) the new normativity of climate ethics; (4) questioning the capitalistic foundation: the four spikes, economic growth, and market failures; and (5) deconstructing normalcy: American disenlightenment vs. global alternatives, and (6) reconceptualizing progress: the fork in the road of the SRES scenarios, and civil evolution. To avoid that the discussion goes all over the place, the six topics are centered around a shared conceptual gravity well. This is the premise of climate philosophy that civilization's clash with planetary boundaries changes everything. The central topic is how to deal with limits that are absolute. And the central demand is to think outside the box.