Science-based understanding of our world is based on reproducibility. A finding or conclusion is tested and tested again by both the original scientist and others in the same and related fields by repetition and exploration of other lines of evidence. (That is the primary difference between science and religion. Science is verifiable by repeated experiment.) When a commentator makes a statement of doubt that contests a fundamental fact of physics it is a sure sign we have entered a parallel universe. Such is the “trace gas” argument.
The argument goes: Carbon dioxide is a trace gas. Because it is a trace gas, comprising only 400 parts per million (PPM) of the atmosphere (0.04%), it cannot possibly be a major player in global warming.
Sue Lani Madsen, a conservative guest columnist for the Spokesman Review, illustrates the “trace gas” argument in her own Spokesman report of an NPR “On Point” Panel in which she participated on September 22, 2017. The topic was wildfires, but her fundamental denial of global warming became a glaring issue. In Ms. Madsen’s Spokesman report describing the event she wrote, “Carbon dioxide is 0.039 percent of Earth’s atmosphere, a trace gas from mostly natural sources.” A likely source of her denialist argument is the “Galileo Movement” in Australia (Galileo would be appalled). Visiting their website is eerily reminiscent of visiting the website of the Flat Earth Society. You can read a little about the Galileo Movement’s arguments and a point by point refutation in an article from Scientific American from August 16, 2011 entitled “Why Carbon Dioxide Is a Greenhouse Gas.”
I was so riled by Ms. Madsen’s denial of basic physical fact I went looking for the original physics research. I found it in the story of the life and work of a British scientist named John Tyndall (1820-1893). Tyndall was a man from a time when men and women (See Eunice Newton Foote in wikipedia) of moderate wealth could advance basic science in home laboratories, a time when scientific discovery was the stuff of popular culture.
The detailing of carbon dioxide as a major greenhouse gas (even when present in “trace” quantities) was simple in concept but challenging in execution. John Tyndall developed an apparatus consisting of a source of heat energy of known intensity, a tube to contain whatever gas or gas mixture Tyndall wished to study, and a device to measure the energy that passed through the gas without being absorbed. Tyndall published his experiments and results in a paper with the distinctly un-sexy name, “On the Absorption and Radiation of Heat by Gases and Vapours, and on the Physical Connexion of Radiation, Absorption, and Conduction.” You can read the actual paper here. (See P.P.S below.) A great summary article on Tyndall’s painstaking work, courtesy of the BBC (on the occasion of the publication’s 150th anniversary) can be read here [highly recommended]. Carbon dioxide was only one of many gases Tyndall studied with his apparatus. This is physics. The results are reproducible, totally independent of denialist claims.
I “know” Tyndall’s results are true not just because I trust the story of Tyndall’s life and work, but because I trust scientists who tried to prove Tyndall wrong…and instead got the same results. (That does not keep modern day denialists from offering nonsensical polemic to cast doubt.)
Had I been brought up to believe that truth emanates only from one holy book, had I not spent much of my youth reading stories of the lives and discoveries of great scientists, I suppose I might consider a 19th century researcher untrustworthy, his experiments somehow motivated by a political or pecuniary agenda and therefor suspect, his results inconsistent with my worldview.
We learn from stories. We “know” what we know because we trust the people who tell those stories. In the case of scientific knowledge we trust not just the people, like Tyndall, who did the foundational physics experiments of atmospheric gases, we trust him because countless others since Tyndall have reproduced and refined his work.
Whenever the “trace gas” argument surfaces it is a marker for ignorance of physical fact.
Keep to the high ground,
P.S. Those who popularize anti-science narratives may be sincere, smug, and confident, motivated and bolstered by the accolades received from their tribe and followers. Projecting nefarious motivations (“Climate Change is a Chinese hoax.”) or delusional thinking on scientists and verified scientific fact is for these folks a satisfying enterprise…and so much easier than actually engaging in scientific endeavor.
P.P.S Scientific papers of Tyndall’s time were presented as narrative stories of the experiments performed. Reading Tyndall’s paper reminds me of the stories that introduced me to the scientific method in my youth. Comparing Tyndall’s paper to modern, dry scientific papers reminds me of the power of narrative to engage the reader. Visit the actual paper here.