Progressive Nation

Issue date: 5/11/08 Section: Opinion

In its last issue, the Princeton Tory ran a misleading article, "Global Warming: A Conflated Orthodoxy." The article represents a narrow interpretation of scientific data, as the authors argue that because historical ice cores show temperature rises before carbon dioxide levels rise, it may not be true that CO2 increases can precede temperature increases and cause global warming. The article glosses over the political reality that many conservatives - George Bush included - now agree that humans do in fact cause greenhouse gas emissions that lead to global warming, and the current debate concerns what steps government should take to combat it.

In the article, Physics Professors Robert Austin and William Happer, who do not study climate but instead issues involving DNA and the spin of atoms respectively, discuss a "phase lag" in the data. The article claims that it takes about "100,000 years" for the CO2 level to increase after warming begins, and since warming precedes a CO2 increase in these examples, Happer asserts that those arguing for human-induced climate change "got it completely backwards." With this technicality in hand, the authors conclude that even though the account of human-caused global warming generally is accepted, the "debate is far from over."

Skeptical of this implication, I talked with Prof. Daniel Sigman, a geosciences professor who researches historical carbon and nutrient cycles, and Gabrielle Dreyfus, a graduate student who studies ice cores that would show these time lags. Both Sigman and Dreyfus agree with the basic observation that CO2 emissions generally appear to rise after warming begins (but with a time lag of closer to 1,000 years if not less; 100,000 years is nearly as long as the time between glacial cycles). They, as well as the recent Intergovernmental Panel on Climate Change (IPCC) report, whose authors won the Nobel Peace Prize, can explain the lag.

The initial warming has long been theorized as a result of what the IPCC report calls the "widely accepted orbital theory" - as the axis of the Earth changes its tilt and wobbles, temperatures can increase. Once temperatures increase, ice melts and ocean patterns change, releasing CO2 into the atmosphere. The CO2 then acts as an "amplifier" leading to further warming, and as the ice cores indicate, CO2 and temperature are highly correlated. The delay can also occur because CO2 can move in and out of ice, so the CO2 is newer than the surrounding ice. And CO2 has been recognized as greenhouse gas since the 19th century. So overall, while the Tory's basic observation of the time lag is true (though not its magnitude), the implication that CO2 will not lead to temperature rise is faulty.

Continued...

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