“But Trace Gas”

CO2 is a tiny part of the atmosphere. Yet it can haz big effects. Which goes on to show that making true claims isn’t enough: one must make relevant ones. This square is a bit silly, but pedagogical. To visualize the effects of carbon dioxide is crucial to make people realize how AGW works.

There is a fine line between arguing from incredulity and incredibilism {1}. Also, it would be hard to argue that CO2 is both a trace gas and essential to life, v. #ButLife. Yet they are often seen hand in hand, or one after the other. Pointing out the contradiction helps.

Examples

So even if Australia somehow completely de-industrialised today and our contribution to global carbon emissions went from 1.3% to 0% a whopping 99.99998% of the atmosphere would be unaffected.

(Evan)

CO2 concentration in Earth’s atmosphere to the nearest hundredth of one percent: 1990: 0.04% […] 2020: 0.04%

(Luis)

Objections and Replies

Amount. There’s so little carbon dioxide in the atmosphere that
☞ Here’s what 400 par per million looks like.

Cause. How can a trace gas suddenly cause a heat wave
☞ Higher average temperatures lead to more frequent extremely hot days.

Energy Imbalance. The 0.5 to 1.0 W/m2 is much smaller
☞ We might not want to observe a planet where energy imbalance is bigger that its natural energy flows. An A/C planet, perhaps?

Impact. CO2’s impact’s so small we barely can trace it
☞ A 2% change in body temperature means death {2}.

Home. There is more CO2 inside your own home due to respiration
☞ The gas in the home does not block infrared radiation to the same extent it blocks them in the atmosphere.

Low. 2 W/m² is too low to meaningfully
It only takes .7 W/m² to in or out of a glacial period. The .2 W/m² adds .12K/decade, and that doesn’t cover the energy passed to other air molecules (Dan).

No explanation. That does not explain anything—
Each part of the Earth’s surface emits heat in the form of infrared (IR) radiation. The peak of this emission is right at the frequency where CO2 absorbs strongly. While the proportion of CO2 in the atmosphere is small, 380 parts per million or 0.038%, this is still a large number of molecules, large enough that near the surface, at wavelengths where CO2 absorbs, the average distance light will travel before being captured is a few meters (a couple of yards). See Eli’s Simplest Explanation for more details.

Smol. 0.04% is small—
Here is what 0.04% looks like. Here is 200, 380 and 600ppm of potassium permanganate. Only a thousandth of 1% of the water on Earth exists as water vapor in the atmosphere. 800 ppm or 0.08% is the limit of alcohol in blood when driving in the US.

Notes

{1} Incredibilism. Rejecting the influence of CO2 on atmosphere is the purest form of climate denial, but sometimes the point only expresses incredulity.

{2} Kooninism. Inferring that because a percentage is small it should have small effects has been known as a kooninism, in honor of Steve Koonin.

Readings

2012-08; Incredibilism.

2010-08; CO2 – An Insignificant Trace Gas? Part One

2010-05; The Simplest Explanation; Eli sometimes can be clear.

Climateball Episodes

2019-06; Kooninisms.