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and hence variations in solar input, were
the major cause of global climate change in
the eons of geologic time that preceded the
last thirty years. The physicist Ilya Usoskin
showed that before 1975 a strong relation-
ship between global warming and changes
in solar radiation existed for more than
a thousand years. However, over the last
thirty years “the climate and solar data di-
verge strongly from each other.” In fact over
the last thirty years solar activity has been
at a minimum. In other words, because of
the greenhouse effect we are out of step
with the natural cycle of solar input to cli-
mate, and this should indeed worry us.
image has proved a lightning rod for global
warming skeptics, because the shape of the
hockey stick becomes less clear depend-
ing on the dataset and statistical methods
used, and the estimated error bars (show-
ing the range of values within which the
answer should fall) are large. Mann's origi-
nal hockey stick was inspired by tree-ring
analyses, based on the assumption that the
nature of the rings reflects growing condi-
tions. The analyses turned out to be faulty
and resulted in a too-smooth curve. None-
theless, many new temperature reconstruc-
tions have been made, and they all show
temperature increases in the twentieth
century, especially since 1970, in much
the same pattern as the original hockey
stick did. The difference is that the origi-
nal hockey-stick shape has been somewhat
blurred. So the bottom line remains the
same: if we look back at the last millen-
nium, we see a significant rise in tempera-
tures in the twentieth century. The hockey
stick limps along.
myth : The hockey stick temperature curve
doesn't exist. The thousand-year tempera-
ture curve proposed by Michael Mann and
made famous by Al Gore was shaped like a
horizontal hockey stick with the upturned,
business end of the stick representing tem-
perature changes in the northern hemi-
sphere during the last hundred years. This
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