By Letter to the Editor on September 7, 2019.
In an Aug. 27 letter to The Herald, Shawn Smith suggested that our understanding of the greenhouse effect here on Earth is an extrapolation from observations of Venus. He goes on to describe concern over the greenhouse effect as “a leap of logic.” In doing so, he is being extremely unfair to the physical sciences community.
The field of molecular spectroscopy, the study of the absorption of radiation by molecules, is well over 100 years old. Similarly, the study of energy transfer between molecules has its roots in early 20th-century science, and has been pursued vigorously since at least the 1960s. Gas dynamics, through which we understand larger-scale transfers of heat and matter in the atmosphere, has been studied seriously since the mid-19th century. I could go on.
We understand the underlying physics of the greenhouse effect very, very well, and our understanding of the relevant processes, at both small and large scales, continues to advance. Expected warming trends are calculated from basic physics, and not extrapolated from a single data point as Mr. Smith suggests.
Mr. Smith’s argument regarding the relative concentrations of carbon dioxide in the Venusian and Earth atmospheres is a seductive one. How could such a small quantity of carbon dioxide have the dramatic effects claimed? The difficulty lies in thinking about balances between heat gained by the atmosphere, in particular by infrared radiation from the Earth’s surface, and heat lost to space. Greenhouse gases act like a blanket, slowing the escape of infrared radiation, one of the planet’s most important means of dissipating heat. If you make the blanket thicker (adding more carbon dioxide), heat escapes more slowly, raising the temperature of the atmosphere.
Our understanding of global warming is based on a great deal of well-understood physics. By adding CO2 to the atmosphere faster than it can be removed, we are thickening the blanket that keeps our planet warm. Whether we like it or not, the physics is inescapable: it’s going to get hotter.
Marc R. Roussel
Professor, Department of Chemistry and Biochemistry
University of Lethbridge