Putting Bullets Holes in the Hockey Stick Model

Fire of Liberty
Dr. Roy Spencer, a principal research scientist for the University of Alabama in Huntsville, has a interesting piece over at TCS Daily that puts a dent in the "hockey stick" temperature curve models that Al Gore and the Green Team seem to cleft to and wave in the face of the media to push an global warming alarmist agenda. While I wish I could write a lot on the subject, I figured I'd let Dr. Spencer (who's further up the scientific ladder than I) fill you in on what the National Academies of Science revealed in its most recent report on the hockey stick model. It's real interesting, so check it out:

For the last several years, the hockey stick has been a poster prop for manmade global warming. For instance, it figures prominently in Al Gore's new movie, "An Inconvenient Truth." But the statistical and data analysis methods that Mann et al. used to arrive at their 1,000 year temperature reconstruction were strongly criticized by some. The hockey stick played down the warmth of the "Medieval Warm Period" of 1,000 years ago, as well as the later coolness of the "Little Ice Age."

Also, the uncritical acceptance of the hockey stick for inclusion in the U.N.'s Third Assessment Report on global climate in 2001 gave many scientists the impression that the editors of that report wanted to believe the hockey stick more than they were convinced of its validity.

In their attempt to not publicly scold Mann and his coauthors for questionable data analysis methods, the authors of the new report instead chose to restate the evidence for how warm the Earth has gotten recently. What the media didn't notice, however, is that the 1,000 year figure that was central to the whole hockey stick debate had now been replaced in the report by a figure of 400 years. Since most of the last 400 years was dominated by the "Little Ice Age," the warming during the 20th century should be welcomed by humanity.

The report says that surface temperature reconstructions before this period (about 1600) have "less confidence" and that "uncertainties...increase substantially backward in time..." for any of these proxy estimates of ancient temperatures. One review panel member told me that the statisticians on the panel were amazed when it was revealed that the method underlying the hockey stick had essentially no statistical skill when validated.

This is pretty harsh language for an NAS report written by review panel members, several of whom are equivalent to foxes guarding the hen house. Researchers who have bought into the validity of using proxy measures for ancient climate reconstructions aren't about to throw away the "best" method the paleoclimate research community has, even if it can not be validated with real temperature measurements (the thermometer was not even invented until the 1600's).

One rather amazing characteristic of the hockey stick is the so-called "divergence problem": the strong warming in the late 20th century is not even indicated in the tree ring data that were used to reconstruct the last 1,000 years of supposed temperature variations. Much of the 20th century warming (the blade of the hockey stick) represents real temperature measurements, not tree ring reconstructions, since they don't show the warming. This raises a natural question, which the panel shrugged off: If tree rings do not show the strong warming of the late 20th century, how do we know there wasn't a similar temperature spike 1,000 years ago?

I'd say that the scientific community is not in such an agreement as Gore and the Green Team would like us to believe. Thanks to folks like Roy Spencer, Bjorn Lomborg(author of The Skeptical Environmentalist), Richard S. Lindzen(Alfred P. Sloan Professor of Atmospheric Science at MIT), Steven F. Hayward and other scientists who continue to apply their scientific knowledge to continue to study the atmosphere rather than jumping to conclusions on global warming like Gore has. A tempered approach is more viable and will be much more frugal than rushing headlong into a problem that might just be a natural occurrence that rolls around every 400 or a thousand years. Sometimes the solution is more harmful than the problem.(That's if you believe there is a pressing problem.)