November environmental column in Chai Notes, the monthly newsletter of Congregation Shir Shalom of Buffalo

A congregant contacted me about a radio talk host who argued that only 3% of the carbon dioxide (CO₂) entering the atmosphere is manmade. How can that small amount account for climate change and the global warming attributed to manmade emissions? Actually, it turns out this is one of the more common arguments used by those who dispute climate change as being human-induced. Not only is it wrong, but it’s misleading.

Carbon dioxide through the greenhouse effect plays a key role in allowing life to exist. Earth’s atmosphere allows to much of the sun’s light to pass through it to heat the Earth’s surface during the day. At night, the warmed Earth surface radiates energy back into space, much like a hot stove does. Fortunately, CO₂ traps some of that radiated (infrared) energy, preventing it from escaping into space, helping to keep our planet warm. This is similar to how a greenhouse works in which glass allows the sunlight in but blocks heat from escaping. The greenhouse effect acts as the Earth’s thermostat, regulating the planet’s surface temperature. Too much CO₂ and the Earth would be too hot, and too little and the Earth would be too cold for life. Natural processes regulate the atmosphere’s CO₂, with plants and the oceans absorbing the CO₂ emitted by animals and other natural phenomena. It’s pretty much a wash, what we call an equilibrium. The levels of CO₂ do rise and fall over time, which helps contribute to natural cycles in the earth’s climate history such as ice ages.

In 1906, the chemist Svante Arrhenius calculated in laborious hand calculations that doubling the concentration of CO₂ in the atmosphere will increase the Earth’s average surface temperatures by about 11⁰F. Our computer models support this calculation. Since 1960, the amount of CO₂ measured in the Earth’s atmosphere has risen by 25%. In 1960, the measured atmospheric concentration of CO₂ was 315 parts per million (ppm). Last year we exceeded 400 ppm. Data collected by ocean buoys and satellites have not been able to identify a natural source for this CO₂ increase. Furthermore, measurements of carbon dioxide isotope ratios in the atmosphere show that this excess CO₂ is not from volcanism or some other source. (If you remember, isotopes are a form of an element like carbon that has additional neutrons in it nucleus. Carbon has three isotopes.)

So, the 3% argument is a bogus argument used to mislead the public. Another way to look at it, think of the old saw about the straw that broke the camel’s back. It just took a little…