Grist: In a major report [PDF] released late last month, the United Nations` Intergovernmental Panel on Climate Change, the world`s leading authority on climate science, told us it was more certain than ever that humans are causing global warming. It also upgraded its projections for sea-level rise by the end of the century, and even broached the subject of climate change`s irreversibility: We may already have done so much harm to the Earth that some of it can`t be undone in our lifetimes, or even in the...