RALEIGH -- Here's a new twist on the now-old debate about climate change and the possibility of human activity pushing up average temperatures via a heightened greenhouse effect.
The conventional wisdom on global warming is been repeated frequently by a gullible popular press and a more-than-willing environmental movement seeking validation for its repudiation of modern American capitalism. It states that rising emissions of carbon dioxide and other greenhouse gases, generated by industrialization and the widespread adoption of the automobile during the 20th century, are creating a warming trend in the atmosphere that if left unchecked could result in rising sea levels, floods, droughts, famines, disease, and more.
The available evidence offers a far more complex series of trends and potential explanations, as my colleague Roy Cordato explained in a JLF Spotlight paper a while back. Readings of ground-level temperature gauges show a warming trend in recent decades but observations at higher elevations show little to no warming. In part, this reflects the so-called "urban heat island" effect generated by growing cities with more concrete and other materials absorbing and radiating heat. The upper-level trend has been difficult to square with the climate-change theory, since the purported cause (industrial and tailpipe emissions) and the purported effect (rising temperatures in the atmosphere) don't appear to coincide.
Other research has pointed to evidence of temperature fluctations far greater than the predicted warming trend that have occurred throughout the history of the Earth, long predating man and his infernal machines. Still other scholars have discovered connections between cycles of sunspot activity and climatic cycles, again challenging the conventional wisdom as to cause. And even for those granting the possibility that recent human activities have been causing recent warming, some have observed that the trend isn't entirely or even mostly unwelcome. Much of the warming has apparently been happening at night and during the winter months, potentially extending the growing season and improving the habitability and agricultural productivity of colder clime. These analysts conclude that efforts to halt the warming through intrusive regulations would impose economic and social costs far greater than realistic estimates of the adverse consequences of global warming itself. Indeed, some have argued that it would be more reasonable for human societies to adapt to such change or to attempt relatively low-cost approaches to reducing its impact.
But now another take on the evidence, as well as some new evidence, suggests that far from being unlikely, human-induced climate change is not only possible but long predates the Industrial Revolution, the automobile, the SUV, clueless Republican presidents, and irresponsible American consumerism. A study published in the journal Climate Change suggests that the natural fluctuations of the Earth's climate would have led to a strong cooling trend several thousand years ago if early human civilizations had not begun the widespread clearing of forestland for agriculture (thus reducing the amount of foliage absorbing carbon dioxide) and the widespread herding of livestock (generating methane, a greenhouse gas). Basically, these ancient terraformers staved off another ice age and thus allowed human civilization to begin and develop, according to the new study.
What do I make of all this? I don't know what to make of it. Other credible researchers cast doubt on the theory that ancient humans were capable of such globe-spanning handiwork, benign as it may have been. Responsible citizenship on this issue means reading widely, thinking critically, avoiding any leaps of logic or jumps to precipitous conclusions, and insisting that ideology-driven activists and politicians stop trying to scare everyone to death.
Hood is president of the John Locke Foundation and publisher of Carolina Journal.
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