By Mike Byron, PhD.
I was astonished to read Alexander Cockburn’s essay in the April 28th online edition of Counterpunch entitled “Is Global Warming a Sin?” [[i]] Cockburn’s thesis is that there is no scientific evidence whatsoever linking anthropogenic (human caused) CO2 emissions with worldwide increases in mean temperature “global warming.” Comparing the proposed sale of carbon credits to alleviate future global warming to the medieval practice of the Catholic Church selling indulgences to cancel past sins, Cockburn asserts:
"There is still zero empirical evidence that anthropogenic production of CO2 is making any measurable contribution to the world's present warming trend. The greenhouse fearmongers rely entirely on unverified, crudely oversimplified computer models to finger mankind's sinful contribution. Devoid of any sustaining scientific basis, carbon trafficking is powered by guilt, credulity, cynicism and greed, just like the old indulgences, though at least the latter produced beautiful monuments." [[ii]]
The Hertzberg-Cockburn Critique of Global Warming
What are these assertions of Hertzberg’s hypothesis? His argument is that temperature changes are driven by long-term changes in the amount of sunlight striking the Earth. These changes are caused by Milankovitch cycles, named for the Serbian scientist who first described them. Wikipedia defines these as follows:
"Milankovitch cycles are the collective effect of changes in the Earth's movements upon its climate, named after Serbian civil engineer and mathematician Milutin Milankovitch. The eccentricity, axial tilt, and precession of the Earth's orbit vary in several patterns, resulting in 100,000 year ice age cycles of the Quaternary glaciation over the last few million years. The Earth's axis completes one full cycle of precession approximately every 26,000 years. At the same time, the elliptical orbit rotates, more slowly, leading to a 22,000 year cycle in the equinoxes. In addition, the angle between Earth's rotational axis and the normal to the plane of its orbit changes from 21.5 degrees to 24.5 degrees and back again on a 41,000 year cycle. Presently, this angle is 23.44 degrees. The Milankovitch theory of climate change is not perfectly worked out; in particular, the largest observed response is at the 100,000 year timescale, but the forcing is apparently small at this scale, in regards to the ice ages. Various feedbacks (from carbon dioxide, or from ice sheet dynamics) are invoked to explain this discrepancy." [[iii]]
Simply put: the Earth’s orbit around the sun varies somewhat with respect to how circular its orbit is, the degree that is poles are tilted with respect to the plane of its orbit, and the position of its poles with respect to the far stars, which “wobbles” (precesses). These several variations occur regularly in cycles of about 22,000, 26,000, 41,000 and 100,000 years. Their composite effect is to vary the amount of sunlight striking the Earth’s surface.
Hertzberg’s assertion is that this process of variation in the strength of sunlight striking the Earth is what drives global climate change. The primary mechanism for this climate change does indeed involve CO2 release in to the atmosphere, according to this thesis. However, the causal order (which variable causes what effect) is reversed from what we would expect:
"Water covers 71 per cent of the surface of the planet. As compared to the atmosphere, there's at least a hundred times more CO2 in the oceans, dissolved as carbonate. As the postglacial thaw progresses the oceans warm up, and some of the dissolved carbon emits into the atmosphere, just like fizz in soda water taken out of the fridge. "So the greenhouse global warming theory has it ass backwards," Hertzberg concludes. "It is the warming of the earth that is causing the increase of carbon dioxide and not the reverse." He has recently had vivid confirmation of that conclusion. Several new papers show that for the last three quarter million years CO2 changes always lag global temperatures by 800 to 2,600 years." [iv]
More sunlight striking the Earth’s surface causes the planet’s oceans, which account for 71 percent of its surface, to heat up. Because the mass of the oceans is much greater than that of the air—about 100 times greater, in fact—there is a considerable lag before oceanic heating becomes sufficient to cause the oceans to release greater amounts of CO2 into the atmosphere. In Hertzberg’s view, the CO2 is an effect and not a cause of global warming.
It is this natural process of variation in sunlight striking the planet, and not anthropogenic CO2 emissions, per Hertzberg, which accounts for the increasing amount of CO2 in the Earth’s atmosphere. To “prove” this point, Cockburn asserts that CO2 emissions fell significantly due to the Great Depression, while temperatures continued to increase, thus “proving” that planet-wide temperature increase is independent of atmospheric CO2 levels.
Cockburn offers several purported examples from the historical record (the Little Ice Age) and the geological record (the Eocene Period) which supposedly further demonstrate the lack of a link between atmospheric CO2 levels and planetary temperature. He is clearly asserting that there is no causal relationship between atmospheric CO2 levels and planetary temperature whatsoever. In other words planetary temperature is independent of CO2 levels in the atmosphere! Not now, not millions of years ago, never, have atmospheric CO2 increases caused temperature increases! That assertion left me stunned, I must admit.
Having discounted anthropogenic effects from having any significant effect whatsoever on the world’s climate, Cockburn then makes a vague reference to the Earth itself as being a cause of planetary warming, asserting: “…the human carbon footprint is of zero consequence amid these huge forces and volumes, and that's not even to mention the role of the giant reactor beneath our feet: the earth's increasingly hot molten core.” Whether the Earth’s allegedly “increasingly hot molten core” plays a role in Hertzberg’s global warming theory, or is just another a priori belief of Cockburn’s is not specified. I will therefore subsequently ignore this vague assertion until and unless Cockburn chooses to be more specific about it.
Hertzberg-Cockburn Critique of Global Warming Rebutted.
First of all, until very recently, human civilization has simply not been of sufficient magnitude to cause any significant effects whatsoever upon global climate and temperatures. Therefore, until very recently, natural forces were wholly responsible for changes in the Earth’s climate and its overall temperature. These natural forces were primarily changes in the amount of sunlight striking the planet due to the Milankovitch cycles. The long lag associated with increasing sunlight warming the Earth and the consequent heating of the oceans and frozen bogs (which release methane a greenhouse gas 30 times more potent that CO2) constitutes a kind of “thermal inertia.” However, as these positive (that is, amplifying) feedback loops kick in, including oceanic warming, ice melting (affecting the planet’s reflectivity) permafrost melting etc., the process of warming begins to accelerate.