In a Boston Globe column titled “Cooler heads prevail against climate panic,” Jeff Jacoby denounces what he deems to be “climate fearmongering” about the dangers posed by unchecked greenhouse gas emissions. I agree that hyperbole is often damaging to public discourse, however Jacoby should acknowledge that misleading and fallacious claims are of equal concern.

We could start with his own suggestion that those concerned about global warming engage in “end-of-the-world doomsaying” akin to Harold Camping's apocalypse prophesies. As a side note, Rush Limbaugh, who's known for his thoughtful and moderate rhetoric, said the same thing a couple weeks ago.

In his column, Jacoby forwards the claim that “rising carbon-dioxide levels” are not “anything to fear,” citing physicist William Happer's assertion that “carbon is the stuff of life.” Jacoby also quotes from Happer's statement that “about fifty million years ago” CO2 levels were “much higher than now. And life flourished abundantly.” (For his part, Happer thinks that those concerned about climate change are far worse than Harold Camping -- they're more like Nazis.)

Jacoby's argument misrepresents the anxieties that so many, including the national science academies of 13 nations and the U.S. military, have about climate change. The existence of Earth or of life itself is not in question. Indeed, if that's the standard for taking action, then I can't think of any tragedy or injustice that would merit concern.

Rather, as scientists contacted through the Climate Science Rapid Response Team explained, climate change demands attention because it is altering the environments in which our societies operate faster than we are adapting, and the transition may be difficult, expensive, and painful in many cases -- all the more so if nothing is done to slow the changes and mitigate our vulnerabilities.

Happer's comparison to the Eocene epoch (56 - 34 million years ago) contributes little to the debate over whether global warming is a serious problem. As Purdue University's Matthew Huber explained via email, the world 50 million years ago was quite a bit different from the one we know, with “crocodiles, palm trees, and ginger plants near the North Pole,” temperatures in continental North America that were 10-15°C warmer, and sea level “about 100m higher.” Needless to say, these are not the assumptions upon which we have built our cities, economies, or food and water systems, and any rapid shift in the climate toward these conditions would cause major disruptions.

Huber, an expert in past warm climates in Earth's history, added that it's a “red herring” to point to the fact that life flourished 50 million years ago, in part because “we are taking global warming that occurred naturally over millions of years and compressing it into several centuries.”

Penn State paleoclimatologist Lee Kump also emphasized this point, explaining that “life had plenty of time to adapt to the rising temperatures and CO2 levels” 50 million years ago, and we are currently driving up CO2 levels “at a much higher rate (centuries rather than millions of years.)” He added, “At this rate life doesn't have the opportunity it had in the Eocene to adapt. Nor do natural systems like the ocean's carbon cycle have time to buffer the change.”

Not to mention that the human population 50 million years ago was zero, whereas during the current period of global climate change, we'll have the well-being of up to 10 billion people to worry about, in addition to the many other species and ecosystems affected.

To bolster his argument that human-caused climate change isn't a serious problem, Jacoby employs some more logical gymnastics:

[W]hy recoil from the modest increase in carbon emissions caused by fossil-fuel use? Because more CO2 means more climate change? Happer shoots down that idea. The earth's climate is always changing, sometimes dramatically. During the medieval warming of a thousand years ago, temperatures were much higher than they are now; during the Little Ice Age six centuries later they were much lower. “Yet there is no evidence for significant increase of CO2 in the medieval warm period, nor for a significant decrease at the time of the subsequent little ice age.''

It's interesting that Jacoby asserts that ”temperatures were much higher than they are now" during the medieval warm period. For their part, climate scientists say the data isn't sufficient to produce a definitive global temperature for that period. According to the National Research Council, “confidence in large-scale surface temperature reconstructions is lower before A.D. 1600 and especially before A.D. 900” due to “the relative scarcity of precisely dated proxy evidence.” However, NRC noted that “presently available evidence indicates that temperatures at many, but not all, individual locations were higher during the past 25 years than during any period of comparable length since A.D. 900.”

But regardless of the global temperature during the medieval warm period, Jacoby presents a fallacious argument when he seeks to refute the notion that “more CO2 means more climate change” by noting that climate change isn't always driven by CO2. That's kind of like denying that your nausea and vomiting were caused by the rotten meat you ate because the last time you had these symptoms, it was morning sickness.

No climate scientist has ever said that CO2 is the only factor influencing the climate. In fact, sorting out the myriad forces involved is exactly what they do. And according to of the University Corporation for Atmospheric Research, studies indicate that “warming by the sun and other variations in natural systems cannot explain” the current period of global warming.

If Jeff Jacoby wants a better discourse about climate change, I'm all for it. As a media figure with a public platform, he can start by accurately characterizing the views of those with which he disagrees, grounding arguments in sound logic, and consulting peer-reviewed science.

UPDATE: In a letter to the editor, Kerry Emanuel, a MIT atmospheric science professor and political conservative, writes that Jacoby “offers us a false choice between panic and the denial of risk.” The letter also states:

[W]e are treated to yet another round of the "climate is always changing,'' rather like a murder defendant telling the jury that people are always dying.

Assessing and dealing with climate risk in an environment of highly uncertain science and expensive options is challenging enough without having to entertain the flippancy of your columnist. There is no scientific basis for his certainty that we have nothing to worry about.