A CO2 Concern - Quareness Series 201st "Lecture".
Somehow in the course of the ongoing contentious Climate Change debate, carbon dioxide (despite being an essential gas necessary for life here on Earth) has increasingly come to be primarily regarded as a pollutant that is the major disrupting agent of the climate. It would appear that the core point of disagreement rests in whether the impact of CO2 on the planet's temperatures may be largely negligible or otherwise. Some on the "less popular" side have argued that the impact is and will remain negligible even if its current concentration in our atmosphere were to double. Is there merit in this view?
Currently the CO2 concentration in the atmosphere at a few thousand feet of elevation is around 430 parts per million. Of course closer to the ground, concentrations can and do vary widely...both by location and the time of day. Any ground-level readings are impacted by photosynthesis and the respiration of insects, etc. And with each of us humans breathing out about 2 pounds of CO2 just in the course of our normal living day...that's not a negligible part of the whole. Could the "net zero" agenda in pushing for the dismantling of our current energy and farming infrastructure (in order to combat climate change) ultimately threaten our very existence? The question of how much CO2 concentration is too high or too low is an important one.
According to climate "alarmism" rising CO2 in linear fashion will result in global warming that will threaten all life on Earth. However, it seems that for every kilometre of altitude we have an average cooling of 6.6 degrees centigrade (known as "the lapse rate") and that cooling continues up to the troposphere (lowest layer of Earth's atmosphere containing around 75% of the mass of its entire atmosphere), where it stops. This cooling is due to the fact that warm air rises and cool air descends (convection). Whilst it's true that as the sun heats the Earth our greenhouse gases (mostly water vapor) do impede cooling, the thermal radiation to space from the Earth (assuming a surface temperature of 15.5 degrees C) has been estimated to be only about 70% of what it would be without those greenhouse gases. The implication here is that the effect of even a doubling of CO2 on our Earth's surface temperature would be negligible given that it might decrease radiation into space by just about 1.1%. It would seem there could be a relatively large effect generated in going from zero CO2 to 400 ppm but a negligible one beyond that e.g. going from 400 ppm to 800 ppm. In layman's terms this would mean that any warming from a doubling of our current concentration of CO2 would not exceed 0.7 degree C...a long way short of the intolerable warming now alarmingly predicted.
There's a potential red flag here if this estimated 0.7 degree C difference is realistic...it would effectively mean that no matter what we do to reduce CO2 emissions it's not going to impact on the climate very much. In order to "get over" this problem it seems that the Intergovernmental Panel on Climate Change (IPCC) may have been assuming substantial positive feedbacks in its projections. And this raises another problem in that most natural feedbacks are known to be negative rather than positive (at least in the worlds of physical chemistry and physics). In fact the said 0.7 degree warming could in itself be an overestimate because there are likely negative feedbacks operating in our very complicated climate system where everything seems to be nonlinear. It was a French chemist Henry Louis Le Chatelier who in 1884 first discovered that when a simple system in thermodynamic equilibrium is subjected to a change in concentration, temperature, volume or pressure...the system changes to a new equilibrium and ...the change partly counteracts the applied change. Could it be that there would be no truly significant climate impact short of getting to absolute zero CO2...when we'd all likely be dead?
A regular reader of the Quareness Series has also recently drawn my attention to this concept of feedback in control systems (thank you Richard) pointing out that in a given system we can have positive or negative. The positive takes the output and adds it to the input resulting in the said output continuing to grow until the system wrecks itself. Negative feedback does the opposite subtracting the output from the input which acts to control the system by keeping the output to a set limit. And as is widely known, our turkeys appear to feel more increasingly secure all the way up to the very time when they are objectively least safe...a somewhat sobering example of the "downside" impact positive feedback can exert.
Perhaps one big lesson to be taken from these concerns/questions about CO2 and Climate Change is that it may be rather unwise to take an "all eggs in the one basket" type approach.
Sean.
Dean of Quareness.
February, 2024.