Eventually, falling levels of sunlight due to these natural cycles reverse the warming process. And that was how it was across countless millions of years, until fossil-fueled human civilization began to become a significant factor affecting the planetary climate in the past 100 or so years.
The primary fallacy in Hertzberg’s thesis is the argument that because natural cycles accounted for all global warming (and cooling) in past ages, it follows that this is still true, and therefore, human activity can be discounted. This fallacy rests upon the supposed lack of any causal relationship between atmospheric CO2 levels and temperature. If this is correct, then our carbon emissions are simply irrelevant to the global climate. Instead, it is asserted by Hertzberg-Cockburn that both planetary temperature and CO2 levels are caused by increasing solar radiation, which by heating the oceans, evaporates more water vapor into the atmosphere. This water vapor is purported to be the actual greenhouse gas, instead of CO2.
Yet CO2 unambiguously does cause heat to be trapped on planetary surfaces. Our nearest planetary neighbor, Venus, is about the same size and mass as the Earth. It is only about 25 million miles nearer to the sun than our planet. Originally, it is believed by planetary scientists to have been temperate with liquid water on its surface about 4 billion years ago. Yet, solar radiation on Venus eventually triggered a runaway greenhouse effect which has cloaked the planet in a dense blanket of CO2 which is about 100 times the thickness of our own atmosphere. The effect of all of this atmospheric CO2 is to make Venus’s present-day surface temperatures hot enough to melt lead! [vi] Such is the global warming power of CO2!
On Earth, the relationship of CO2 and temperature since the industrial revolution began is quite clear, as shown in the figure below:
Source: Whole-systems.org [[vii]]
What we need to understand is that with the onset of the Industrial Revolution something new and unprecedented occurred: anthropogenic CO2 releases compounding over a brief time interval triggered escalating temperature increases, along with overall climate change on a global scale. There is no thousand-year lag in this relationship, simply because the triggering agent is not gradually increasing levels of sunlight; rather, it is humans burning fossil fuels, thereby rapidly releasing carbon into the atmosphere. A thousand year lag is evidence of natural climate change. Rapid onset temperature increases are evidence of something unnatural at work: human civilization.
We know where all of this CO2 which suddenly appeared in or atmosphere comes from: it comes from the fossil fuels we’ve just burned for energy. Period. It is not caused by increasing levels of sunlight. As we shall see presently, these levels have actually been decreasing in recent decades!
We know the physics of CO2 with respect to its trapping heat in the atmosphere. It is the same on Earth as it is on Venus, because the laws of physics are universal. Contrary to Hertzberg’s assertion, climate models do indeed account for water vapor in the atmosphere. They may do this imperfectly, however this is a far cry from asserting that these models “fail to account for” this greenhouse gas.
As to the assertion that declines in the rate of CO2 emissions during the Great Depression did not cause corresponding temperature decreases, Cockburn fails to understand that CO2 concentrations are cumulative. Once released, the gas remains in the atmosphere for centuries—unlike water vapor, which quickly precipitates out of the atmosphere as rain or snow. Temperatures did not fall because, although there was a slowdown in atmospheric buildup of CO2, overall levels of CO2 in the atmosphere were still increasing.
Interestingly, the graph above seems to show a pause in temperature increases, just after the Depression induced slowdown of CO2 emissions. This relationship is what would be expected to be seen if CO2 levels did indeed directly affect temperatures. It certainly does not disprove a causal relationship, as Cockburn misguidedly asserts.
Finally, I would note that throughout recent decades, the amount of sunlight striking the Earth’s surface has actually been diminishing, not increasing, as Cockburn asserts. This process is called global dimming. [viii] It is also anthropogenic, as it is caused by atmospheric pollutants blocking sunlight from striking the Earth’s surface. If the Hertzberg-Cockburn theory were correct, it would follow logically that planetary temperatures would decrease due to global dimming, and not increase as they have done.
Empirical observation thus falsifies the Hertzberg-Cockburn theory. In fact, observation shows that nature behaves exactly as anticipated if the causal relationship of CO2 and temperature were both true and a major climate factor.
Conclusion
In summary, the Hertzberg-Cockburn thesis is falsified by empirical data. The Hertzberg-Cockburn thesis conflates natural and human-caused climate change, while ignoring the fact that this latter process has massively overridden all natural climatic factors. It has also ignored or conflated with natural cycles, anthropogenic factors which act to cool the planet such as pollution-caused global dimming.
Why has Alexander Cockburn made and publicized this unfounded assertion? I believe him to be a decent and honest man. I certainly do not believe that he is, for example, a paid disinformation agent, or something along those unsavory lines.
