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Carbon Dioxide and Air Temperature: Who Leads and Who Follows?

Which came first:  The chicken or the egg?

By: David R. Legates

In the era of climate change, this age-old question has received a new facelift. Now it becomes—Which came first:  The rise in carbon dioxide or the rise in air temperature?

Since the dawn of climate change alarmism, we have been told that carbon dioxide is the driver of climate change. Increase carbon dioxide, and consequently, air temperature increases. So, if we decrease the carbon dioxide in the atmosphere, it stands to reason that global warming will be abated. It’s just that simple.

Or is it? Many climatologists have noted that carbon dioxide is not the climate change driver alarmists purport it to be. An article in the Epoch Times suggests that a fixation on carbon dioxide ignores the real drivers of air temperature, which include the Sun and natural variability. But the idea that carbon dioxide is somehow the climate change control knob does not die easily.

In 2007, Laurie David and Cambria Gordon published a book entitled The Down-to-Earth Guide to Global Warming. It was billed as “from the producer of [Al Gore’s] An Inconvenient Truth comes a powerful, kid-friendly, and engaging book that will get kids get [sic] interested in the environment!”  On page 18, a flap instructs children to “lift to see how well CO2 and temperature go together.”  The graph that becomes exposed shows that as time passes over the last 650,000 years, “the more the carbon dioxide in the atmosphere, the higher the temperature climbed…the less carbon dioxide, the more the temperature fell…by connecting rising CO2 to rising temperature scientists have discovered the link between greenhouse-gas pollution and global warming.”

The figure is from an article in Science by Fischer and colleagues in 1999.The problem is that the axes are mislabeled in The Down-to-Earth Guide—the air temperature axis is labelled “CO2 concentration in the atmosphere” while the carbon dioxide axis is labelled “climate temperature”. As the Science article noted, “High-resolution records from Antarctic ice cores show that carbon dioxide concentrations increased…600 ± 400 years after the warming of the last three deglaciations.”

Subsequent research has confirmed that carbon dioxide follows and does not lead to atmospheric air temperature. For example, in an article in Science in 2001, the authors include a graph that shows carbon dioxide concentrations following air temperature by a period of less than 1000 years. Another article in Science in 2003 concluded that “the CO2 increase lagged Antarctic deglacial warming by 800 ± 200 years”. A review paper in 2007 concluded that little evidence exists that greenhouse gases “have accounted for even as much as half of the reconstructed glacial-interglacial temperature changes”. Another paper in Science in 2007 wrote that the East Antarctica ice core “shows no indication that greenhouse gases have played a key role in such a coupling [with air temperature].”  A more recent study by W. Jackson Davis in 2017 concluded that “changes in atmospheric CO2 concentration did not cause temperature change in the ancient climate”.

I have been writing that CO2 is not a magic climate change control knob for more than a decade. Rather than being a pollutant, carbon dioxide is food for plants. This is good news for animal life and humans as well. We must stop the demonization of carbon dioxide and embrace its effects as the whole biosphere benefits from additional carbon dioxide.

David R. Legates is an emeritus professor at the University of Delaware and is the Director of Research and Education at the Cornwall Alliance for the Stewardship of Creation. He also is an Advisory Board Member of A Better Delaware.