Annals of the Former World, by John McPhee. Compendium of geologic writings by master nonfiction writer.
Global Warming : The Complete Briefing, by J. T. Houghton. High points from the scientific reports of the IPCC, the Intergovernmental Panel on Climate Change.
Is the Temperature Rising? : The Uncertain Science of Global Warming, by S. George Philander. Readable non-specialist's introduction to global-warming science written by leading El Nino researcher.
Guns, Germs, and Steel : The Fates of Human Societies, by Jared Diamond. Absorbing narrative of how environmental factors may have led to differences in culture and competition between human societies.
Wonderful Life : The Burgess Shale and the Nature of History, by Stephen Jay Gould. Speculations on early evolution.
Noah's Flood : The New Scientific Discoveries About the Event That Changed History, by Walter C. Pitman, William B. F. Ryan. This year's airplane-read in the US Geological Society.
T. Rex and the Crater of Doom, by Walter Alvarez. The story of the K/T boundary meteor from the guy who discovered the iridium spike.
Climate, History and the Modern World, by H. H. Lamb. Treatise on how climate and human history interact. Heavy on detail.