The Beginnings of Climate Science
Carbon dioxide is the major regulator, the thermostat, of earth’s atmosphere. That fact was demonstrated by John Tyndall, a British physicist, in experiments done in his laboratory in the 1850s. Using an apparatus one could reproduce today for a few thousand dollars, he showed infrared radiation (heat) passes unimpeded through 99% of the atmosphere (oxygen and nitrogen gases percentages combined), whereas carbon dioxide, even in low concentrations, absorbs infrared wavelengths, i.e. traps heat. (Light energy from the sun [literally a spectrum of wavelengths] passes to the earth’s surface with little absorption, bringing the energy that carbon dioxide then traps as heat, hence the name “greenhouse gas.”) Far more sophisticated research has been done since, but Tyndall’s work was the original demonstration.
It is with sadness and alarm I encounter people today who parrot “but carbon dioxide is just a trace gas” as a fundamental objection to the whole of climate science. Are these the same people who claim the earth is flat? Worse, otherwise respectable media publish such inanity, lending uncritical approval to misinformation and doubt. The basic science is irrefutable, repeatable by experiment. That is how science works. No amount of bloviation from people who missed out on a basic physics education can change that, but offering them an uncritical forum will endanger us all. (By all means offer them a forum, that is their “first amendment right,” but how about a little checking of basic fact?)
Keep to the high ground,
P.S. Another tack is to offer an analogy. If you are looking for a monumental effect of something present only in "trace" quantities, consider Fentanyl, an intravenously administered rapid-acting opiate useful in medicine, but also the causative agent in many drug overdose deaths.
Five hundred micrograms of Fentanyl will kill a person by shutting down respiration. The classical “standard” man is 70 kilograms (154 pounds). If you do the math, that dose of Fentanyl represents 0.000000714% of this man’s body weight, or about 0.7 parts per million (ppm), roughly 1 ppm. Tell me again why 400 parts per million is too small to be causing a problem. The CO2 in the atmosphere is at a concentration 500 times higher than the lethal dose of Fentanyl.
Let’s take the analogy further. Under the guidance of an anesthetist 50 micrograms of Fentanyl (a tenth the lethal dose) is very safe and very useful in relieving the discomfort from injecting anesthetic behind an eye to lay down anesthetic for eye surgery. (Even so, respiration is carefully monitored.)
Similarly, a small dose of CO2 in the atmosphere has been good to us. The 250 parts per million of CO2 in the atmosphere has been the concentration of CO2 in the last few thousand years of recorded history. That is just enough concentration of CO2 to keep us in the sweet zone of temperature we’ve mostly enjoyed several thousand years (8000 years from the close of the last ice age—when CO2 levels were even lower). Since the industrial revolution we’ve added another blanket to our atmospheric bed clothes by burning fossilized carbon and spiking the concentration to over 400.