Even yellow journalists know it’s a good idea to use the refereed scientific literature as the basis for science stories, so it was disconcerting to see a bona fide green journalist like the Washington Post’s Joby Warrick give a great deal of ink to a nonrefereed speech — not even a paper — delivered in San Francisco by federal climatologist Jonathan Overpeck.
The reason for all the fuss soon became obvious. At the December meeting of the American Geophysical Union, Overpeck said that the so‐called Medieval Warm Period was local, not global. In other words, the warming that was so substantial that it allowed the Vikings to colonize Greenland and North America was not created by a general planetary warming. That implies that the cooling that followed — known as the Little Ice Age — was similarly non‐global; otherwise the Warm Period would have shown up, in comparison with temperatures in succeeding centuries as, well, global warming.
Overpeck’s speech prompted handsprings of joy from our greener friends. Now, instead of saying that the decade of the 1990s (and, in particular, 1998) is the warmest in 600 years (which goes back to the beginning of the putative Warm Period), they can say it’s the warmest in 1,200 years. This story will be in print on or about January 4, 1999, and allows them to declare that the warm terror is here and higher taxes are needed pronto to stop the burning of fossil fuels.
Others might say, “big deal, sure am glad that I haven’t spent a lick on heating oil and it’s almost Christmas. Think I’ll go and buy some stuff for the missus.”
Like Tip O’Neill’s politics, climate is local.
Still others may correctly deduce that Overpeck has created a big problem for those who warn of impending apocalypse. If he is right (a large IF), then regional climate naturally varies tremendously, whether or not the globe warms. In other words, climate changes so dramatic that they promoted the Viking exploration are simply the way of things. And ditto for their flipside — large regional coolings like the Little Ice Age. That event sent the Rhone Glacier in the Alps some 5,000 feet further downslope than it is today and prompted winter carnivals on the frozen Thames.
Poignant testimony to the social consequences of this regional swing can be found in Kalaallit Nunaat (the politically correct term for Greenland these days), where masonry churches, once built in pastures, are now encased in ice. While KN’s climate clearly changed in ways that were tremendously important to society at the time of the Vikings, that apparently had nothing to do with global warming or cooling.
Instead, Overpeck says, those changes occurred as purely internal oscillations of the climate system, with no external global change. If we accept that notion, what does it really mean?
It means that large, regional climate changes have occurred and will occur whether or not the planet warms. That is the kind of change people and plants care about, because no one can sense the global temperature. Like Tip O’Neill’s politics, climate is local. So those who would seek to impose costs on society to prevent climate change had better demonstrate that warming the planet will make large regional excursions more, not less, likely.
Recently, I explored this notion in a paper in the refereed journal Climate Research. Relying upon historical data (and explicitly ignoring computer models of climate because of their patent unreality), I 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 I looked at the variability as a function of the planet’s annual temperature, I found that the cool years were more variable and the warmer ones less. Conclusion? Warming the planet decreases variability on a year‐to‐year scale. Cooling the planet makes things more variable.
That’s pretty good evidence that what human beings are doing to the climate makes things more predictable and equable than before.
Want more? When the carbon dioxide concentration of the atmosphere was at its highest level since animals first appeared, the biggest animals in history roamed the earth: dinosaurs. Those beasts required a tremendous amount of vegetation to reach their enormous size. Carnivores, like T. Rex, were supported by the massive herbivores. How many tons of vegetation were ultimately required to feed them, considering it had to pass through huge lunks like Apatosaurus (that’s Brontosaurus to you intellectual dinosaurs)? The toasty earth had to have been greener than casino felt.
What’s more, when the dinos were around, the climate was so stable that they were cold blooded! They’d probably still be here today, except for the fact that they went extinct when the earth got clobbered by a small asteroid. The 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.
Our greener friends might become extinct too, if they tout Overpeck’s findings as good news for their side.