Longer-term perspective on global warming (and other catastrophes)

On March 16th I blogged about the sharp upturn in global temperatures that some liken to the blade of a hockey stick. The blog provides a link to a graph reproduced by the BBC which goes back 1000 years. Aside from questions about how data are fitted, simple changes to scales and other attributes of the graphs themselves can paint very different perspectives on seemingly straightforward scientific questions such as whether we ought to be worried about global warming. Andy Sleeper shows this in part 7 of his white paper titled HOW TO LIE WITH STATISTICAL GRAPHICS. The color-coded graph generated by the U.S. National Oceanographic and Atmospheric Administration is very alarming. However, it only provides 122 years of history and the y-axis scale is restricted to about 2 degrees C. A few figures later in Sleeper's paper one sees another graph based on 400,000 years of temperatures estimated from core samples of Antarctic ice. It reveals cyclic temperature swings of 12 degrees C! In this context, should a less than 1 degree increase in global temperature be considered abnormal, that is, due to a special cause such as man-made carbon dioxide?

PS. Here's something to really worry about. The November issue of Sky and Telescope features a heads-up on "The Most Dangerous Asteroid Ever Found" -- a 1000-foot pile of rock called Apophis. It will just miss the Earth on April 13, 2029. If Apophis hits a narrow zone -- called the keyhole, it will be dragged enough by our gravity to put it on a course that collides with Earth seven years later. One can only hope that NASA's proposed gravity tractor will pull the asteroid off target and save the planet.