What is normal? Maybe continuous change is the only thing that qualifies. There’s been warming over the past 150 years and even though it’s less than one degree, Celsius, something had to cause it. The usual suspect is the “greenhouse effect,” various atmospheric gases trapping solar energy, preventing it being reflected back into space.
We ask Bryson what could be making the key difference:
Q: Could you rank the things that have the most significant impact and where would you put carbon dioxide on the list?
A: Well let me give you one fact first. In the first 30 feet of the atmosphere, on the average, outward radiation from the Earth, which is what CO2 is supposed to affect, how much [of the reflected energy] is absorbed by water vapor? In the first 30 feet, 80 percent, okay?
Q: Eighty percent of the heat radiated back from the surface is absorbed in the first 30 feet by water vapor…
A: And how much is absorbed by carbon dioxide? Eight hundredths of one percent. One one-thousandth as important as water vapor. You can go outside and spit and have the same effect as doubling carbon dioxide.
This begs questions about the widely publicized mathematical models researchers run through supercomputers to generate climate scenarios 50 or 100 years in the future. Bryson says the data fed into the computers overemphasizes carbon dioxide and accounts poorly for the effects of clouds—water vapor. Asked to evaluate the models’ long-range predictive ability, he answers with another question: “Do you believe a five-day forecast?”
Bryson says he looks in the opposite direction, at past climate conditions, for clues to future climate behavior. Trying that approach in the weeks following our interview, Wisconsin Energy Cooperative News soon found six separate papers about Antarctic ice core studies, published in peer-reviewed scientific journals between 1999 and 2006. The ice core data allowed researchers to examine multiple climate changes reaching back over the past 650,000 years. All six studies found atmospheric carbon dioxide concentrations tracking closely with temperatures, but with CO2 lagging behind changes in temperature, rather than leading them. The time lag between temperatures moving up—or down—and carbon dioxide following ranged from a few hundred to a few thousand years.