Scientific American: James Hansen has been publicly speaking about climate change since 1988. The NASA climatologist testified to Congress that year and he's been testifying ever since to crowds large and small, most recently to a small gathering of religious leaders outside the White House last week. The grandfatherly scientist has the long face of a man used to seeing bad news in the numbers and speaks with the thick, even cadence of the northern Midwest, where he grew up, a trait that also helps ensure that his sometimes...