Logic Goes Extinct As Press
Overplays Overpeck
Federal climatologist Jonathan Overpeck
is in danger of replacing NASAs James Hansen as the 1998 Apocalyst
Poster Child. Overpeck recently released a spate of papers and conference
presentations about past and future climate.
In the Bulletin of the American
Meteorological Society, for example, he argued that, with or
without human-induced global warming, were headed for some
tremendous droughts next century. And, of course, the greenhouse
effect will make things even worse!
And in an earlier presentation at the
December meeting of the American Geophysical Union, Overpeck asserted
the so-called Medieval Warm Period was local, not global. Well
concentrate on that one here.
His bombshell concept is that the Medieval
warming was so substantial that it allowed the Vikings to sail westward
without freezing to death, colonizing Greenland and North America,
but it was not created by a general planetary warming. This theory
implies that the Little Ice Age, the cooling that later decolonized
that area, was similarly nonglobal; otherwise the Warm Period would
have shown up as, well, global warming, compared with succeeding
centuries.
Overpecks speech prompted handsprings
of joy from our greener friends. Now, instead of saying that the
1990s (and, in particular, 1998) are the warmest in 600 years (which
goes back to the beginning of the putative Warm Period), they can
say theyre the warmest in 1,200 years. "Obviously,"
they can remark, "the Warm Terror is here and we need to raise
taxes pronto to stop the burning of fossil fuels."
Others might say, "Sure am glad
I havent spent a lick on heating oil and its almost
Christmas. Think Ill go and buy some stuff for the missus."
Still others, somewhat more penurious
and even-headed, realize that Overpeck has created the apocalysts
biggest nightmare. If hes right, then regional climate
naturally varies tremendously, whether or not the globe warms. Climate
changes so dramatic that they promoted Viking exploration are simply
the way of things. And ditto for their flipsidelarge regional
coolings such as the Little Ice Age, an event that sent the Rhone
Glacier in the Alps some 5,000 feet farther downslope than it is
today.
Poignant testimony to the social consequences
of this regional swing can be found in Kalaallit Nunaat (Thats
politically correctese for Greenland these days), where masonry
churches, once built in pastures, are now encased in ice. While
K.Ns climate clearly changed in ways that were tremendously
important to society in Viking times, this apparently had nothing
to do with global warming or cooling.
Instead, Overpeck says, these changes
occurred as pure internal oscillations of the climate system, with
no external global change.
If we accept the notion that large
regional changes in climate are independent of the global temperature,
what does it really mean? Forecast climate changes of the magnitude
that is driving the current hysteria will occur whether or not
the planet warms. Further, those who would seek to impose costs
on society now must demonstrate that warming the planet will make
these changes more, not less, likely.
We recently explored this notion in
the refereed literature. Relying upon data (and explicitly ignoring
computer models of climate because of their patent unreality), we
found that temperature variability between seasons and between years
has significantly declined in the second half of this century. And
there have been a few warm years in that period, too.
So, when we looked at the variability
as a function of the planets annual temperature, we found
that the cool years were more variable and the warmer ones less
so, as our figure shows. Conclusion? Warming the planet decreases
variability on a year-to-year scale. Cooling the planet makes things
more variable.
Figure 1. Our recent look into the relationship between global
temperatures and temperature variability showed that higher temperatures
are associated with less temperature variability and lower
temperatures.
We think thats pretty good evidence
that what human beings are doing to the climate makes things more
predictable and equable than before.
Want more evidence? When the atmospheres
carbon dioxide concentration was at its highest level since animals
first appeared, the largest animals in history roamed the earth:
dinosaurs. These beasts required a tremendous amount of vegetation
to reach their enormous size. Carnivores such as T. rex were in
turn supported by the massive herbivores. How many tons of vegetation
were ultimately required to feed him, considering it had to pass
through huge lunks like Apatosaurus? (Thats Brontosaurus to
you intellectual dinosaurs.) The earth had to have been greened
beyond recognition.
Whats more, when the dinos were
around, the climate was so stable that they were cold-blooded! Theyd
probably still be here today if they hadnt gone extinct when
the earth got clobbered by a small asteroid. Said asteroid raised
a huge cloud of dust and killed them with global cooling, which
made the climate more variable, resulting in an undependable food
supply.
We think our greener friends might
go extinct too if they tout Overpecks findings as good news
for their side.
References:
Overpeck, J.T., 1998, How unprecedented
is recent Arctic warming: A look back to the medieval Warm Period.
Presented to the Fall Meeting of the American Geophysical Union,
San Francisco, Calif.
Michaels, P.J., et al., 1998, Analysis
of trends in the variability of daily and monthly historical temperature
measurements. Climate Research, 10, 2733.
[December 28, 1998 World
Climate Report, Vol. 4, No. 8]
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