From the Babylon of Gilgamesh to the post-Eden of Noah, every age has viewed climate change cataclysmically, as retribution for human greed and sinfulness.
In the 1970s, the fear was "global cooling." The Christian Science Monitor then declaimed, "Warning: Earth's climate is changing faster than even experts expect," while The New York Times announced, "A major cooling of the climate is widely considered inevitable." Sound familiar? Global warming represents the latest doom-laden "crisis," one demanding sacrifice to Gaia for our wicked fossil-fuel-driven ways.
But neither history nor science bolsters such an apocalyptic faith.
History and Science
Extreme weather events are ever present, and there is no evidence of systematic increases. Outside the tropics, variability should decrease in a warmer world. If this is a "crisis," then the world is in permanent "crisis," but will be less prone to "crisis" with warming.
Sea levels have been rising since the end of the last ice age, most rapidly about 12,000 years ago. In recent centuries, the average rate has been relatively uniform. The rate was higher during the first half of the 20th century than during the second. At around a couple of millimeters per year, it is a residual of much larger positive and negative changes locally. The risk from global warming is less than that from other factors (primarily geological).
The impact on agriculture is equivocal. India warmed during the second half of the 20th century, yet agricultural output increased markedly. The impact on disease is dubious. Infectious diseases, like malaria, are not so much a matter of temperature as of poverty and public health. Malaria remains endemic in Siberia, and was once so in Michigan and Europe. Exposure to cold is generally more dangerous.
So, does the claim that humans are the primary cause of recent warming imply "crisis"? The impact on temperature per unit CO2 goes down, not up, with increasing CO2. The role of human-induced greenhouse gases does not relate directly to emission rate, nor even to CO2 levels, but rather to the radiative (or greenhouse) impact. Doubling CO2 is a convenient benchmark. It is claimed, on the basis of computer models, that this should lead to 1.1 - 6.4 C warming.
Philip Stott is an Emeritus Professor from the University of London, UK. For the last 18 years he was the editor of the Journal of Biogeography. For more information about the debate series, go to www.iq2us.org
What is rarely noted is that we are already three-quarters of the way into this in terms of radiative forcing, but we have only witnessed a 0.6 (+/-0.2) C rise, and there is no reason to suppose that all of this is due to humans.
Indeed the system requires no external driver to fluctuate by a fraction of a degree because of ocean disequilibrium with the atmosphere. There are also alternative drivers relating to cosmic rays, the sun, water vapor and clouds. Moreover, it is worth remembering that modelers even find it difficult to account for the medieval warm period.
The Real Crisis
Our so-called "crisis" is thus neither a product of current observations nor of projections.
But does it matter if global warming is a "crisis" or not? Aren't we threatened by a serious temperature rise? Shouldn't we act anyway, because we are stewards of the environment?