The hokey hockey stick

Vincent J. Curtis

25 Nov 2018

When people think of global warming, most think of the hockey stick graph.  This graph, produced by Michael Mann from a study of tree rings, shows essentially constant temperatures from 1000 A.D. to 1950, followed by an sharp increase.  This hockey stick graph is claimed to show the evil effects on global temperature of the industrialization of the western world, particularly of the United States.

To the discerning eye, the graph seemed odd.  It failed to show the medieval warm period (950 – 1250) and the little ice age (1300 – 1850), which are well known and well documented phenomena.  The business of calibrating the thickness of a tree ring to an average annual temperature seemed to make dramatic assumptions about other growth factors, such a sunlight, rainfall, species of tree, and local accidents of fertilization.  In addition, trees only cover about 15 % of the earth’s surface.  The oceans cover about 70 percent of the surface; there are no trees in the Antarctic, the Arctic, and the great deserts of the world; and the question of representativeness arises.

Then there is the problem of accuracy of measurement.  Tree rings are irregular in shape, vary greatly in thickness around the tree, and, most importantly, the boundary of a ring is not sharp.  The black hash mark on a wide-range mercury thermometer enables an observer to read temperatures reliably to within half, or maybe a quarter of a degree.  Yet the hockey stick graph confidently showed temperature to hundredths of a degree!

Some funny things started to happen.  Ross McKitrick, a professor of economics at the University of Guelph showed that the sampling and the way Mann handled the data would have produced a hockey-stick graph regardless of the input data.  Then, Mann’s original raw data set was “lost” and all that was available to other researchers was Mann’s processed data set.

Then it became clear that Mann had used not tree-ring data for the twentieth century temperatures but thermometric data instead.  The thermometric data showed an increase in temperature – while the tree ring data showed a decrease in temperature!  Mann used the thermometric data on the grounds that it was more reliable, even if the graph is lacking in consistency.

Mann’s hockey stick graph is insufficient on which to base wide-ranging political or economic decisions, for it demonstrates nothing scientifically.  In the first place, it offers no cause.  Nobody has duplicated Mann’s work.  Even more important is the failure to detect the two large natural variations in global average temperature; the medieval warm period and the little ice age.  Had these been plotted on Mann’s graph, the increase shown from 1950 could be inconveniently interpreted as another example of natural variation.

Mann’s graph, which demonstrates no cause-effect relationship, has been seized upon for political purposes, and raises the question of whether it was created to feed into a political narrative that had been fermenting since the late 1980’s.  An admission of natural variation of global average temperature would vex the narrative that immoderate economic success by the United States in particular was endangering the future of the world.

Between 1940 and 1970, global average temperatures fell, which gave rise to the global cooling scare of the 1970s.  The extinction of the dinosaurs was claimed to have been caused by the global cooling caused by a meteor impact, and a “nuclear winter” was feared as a result of a war caused by Ronald Reagan.  After it became clear that global temperatures were warming again, Dr. James Hansen of NASA in 1988 advanced the global warming caused by American industrial activity hypothesis.  Since 1998, however, satellite measurements of average global temperatures has shown no increase – a twenty year pause in global warming.

The utter politicization of the global warming issue has poisoned “climate science.”  As revealed in the climategate emails, legitimate scientists who wanted to study natural variability were driven out of the field by sordid means to protect the political narrative.

Real science doesn’t offer opinions.  It doesn’t fear contradiction.  Climate science has to dissociate itself from the hockey stick graph, from rampant data manipulation, and from far-fetched forecasts of catastrophe that cannot be scientifically demonstrated.

-30-

.