The Climate Control Knob
Can trace levels of CO2 really control the climate?
‘‘…when making up 0.03% of the atmosphere, CO2 is apparently fine. But at 0.04%, we’re facing a catastrophe. Wait, what!?’’
Even at such trace amounts, does carbon dioxide control the Earth’s temperature?
Greenhouse theory suggests so.
But do the observations show that CO2 is effectively the Earth’s climate control knob?
Here, I argue that they do not.
CO2 at ‘Unprecedented’ levels
The US space exploration agency, NASA, announced back in 2013 that concentrations of carbon dioxide in the atmosphere “had reached 400ppm for the first time in recorded history.”
At the beginning of the 20th century, prior to the commencement of large-scale fossil fuel burning, atmospheric CO2 concentrations were around 300ppm. The next 100 years have seen the release of CO2 into the atmosphere from fossil fuel burning on an ever increasing scale. NASA's announcement of the 400ppm threshold being breached represented a seemingly alarming 33% increase.
But what does 400ppm actually mean? Is it a lot? Is it enough to control the temperature of the planet?
What is a “ppm” ?
Meaning parts per million, ppm is a measurement that describes a ratio of, in this case, one type of gas (CO2) within an overall mixture of gasses (the general ambient air). When describing concentrations with lower orders of magnitude, it can be more convenient to use ‘parts per billion’ (ppb), and for orders of magnitude higher, ‘percentages’ are often used.
If 400ppm sounds like a big number, 400,000ppb sounds like a really big number. But 0.04% sounds fairly insignificant. Of course, they are all precisely the same! Here we can see that understanding the scientific notation is crucial.
Is 400ppm a lot?
For context:
In a human breath there is a CO2 concentration of approximately 40,000ppm
Indoor CO2 levels in well-ventilated rooms are normally at around 400-600ppm, and levels of up to 1,000ppm would not be uncommon
The concentration of CO2 needed to sustain plant life is approximately 150-180ppm
CO2 concentrations in excess of 1,000ppm can typically be found in greenhouses
400ppm means that there are 40 molecules of CO2 out of every 100,000 molecules of ambient air. It would be the equivalent of having 40 people randomly dispersed around England's Wembley football 100,000-seater stadium, for example.
But remember, human activity is not responsible for putting all 4 of these CO2 molecules (out of every 10,000 ambient air molecules) into the atmosphere. There are natural sources (and sinks) of CO2.
In fact, natural cycles of CO2 between the soils, seas, and atmosphere are orders of magnitude greater than that emitted from fossil fuel burning.
Human activities have therefore added the additional 100ppm of CO2 on top of the naturally occurring 300ppm of CO2.
The diagram below attempts to illustrate this point further. In the image, there are 3 green dots that represent these natural “background” CO2 molecules, and the 10,000 (trust me!) blue dots represent the general ambient air molecules. There is a single red dot which represents the additional molecule that human activity has added over the last century or so.
The current consensus view is that this additional, single molecule of CO2 out of every 10,000 molecules of ambient air is having a significant, even catastrophic warming effect through an exacerbated “greenhouse effect,”.
In other words, when making up 0.03% of the atmosphere, CO2 is apparently fine. But at 0.04%, we’re facing a catastrophe. Wait, what?!
This suggests extreme temperature sensitivity to increasing, albeit still trace levels of CO2 in the Earth’s atmosphere.
But is there evidence for such sensitivity?
Well, yes there is evidence, seemingly an endless supply, but how convincing it is is a matter of opinion.
One of the reasons why the climate debate remains alive is that, when relying purely on correlation between large, extremely variable temperature measurement data sets and CO2 concentrations, it is always possible to find alternative data sets that go against the claim. This is a very complex area of climate science, and I will not get deeper into it here, other that to reiterate:
‘‘Correlation is not causation!’’
Moreover:
1. Do not assume that you will be swimming against the tide of the overwhelming consensus of experts in questioning such high sensitivity to CO2 changes, despite the powerful “97% of climate scientists agree” claims. In fact, you would be in very good company, including respected academics and even Nobel prize winning physicists. (The ‘consensus’ claim will be the topic of a future article).
2. Consider that the planet has experienced CO2 concentrations as high as 7,000ppm in geological history. At around 4,000ppm, the Earth once plunged into an ice age! So here we are talking not about a CO2 increase of 0.01% as we have witnessed over the last century, but increases of thousands of percent over today's levels without there being a corresponding correlation with the Earth's climate. See here and here for more information about climate conditions over geological time frames.
3. We are experiencing the highest known CO2 concentrations within our current geological “epoch” (the Holocene), but not the highest temperatures. Higher temperatures were associated with the Medieval Warm Period and the Roman Warm Period, for example.
4. CO2 is not the most important greenhouse gas—that accolade is given to water vapor. Would it not follow, therefore, that the much more abundant and potent water vapor greenhouse gas would effectively override any warming effects from the relatively weak, trace amounts of human-produced CO2?
5. There are other natural phenomena that influence the Earth's climate: solar winds, urban heat islands, the Earth's orbital cycles, volcanic activity, and cloud cover to name but a few. Exactly to what extent trace concentrations of CO2 influence the climate, if any, relative to all of the other factors which are rarely constant and often difficult to quantify, and may even be beyond our current limits of understanding.
Key Points:
- Atmospheric CO2 concentrations have increased from 300ppm to above 400ppm today, with the burning of fossil fuels widely accepted as being responsible for the majority of the increase.
- The additional 100ppm added by human activity is the equivalent of one molecule of CO2 out of every 10,000 molecules of ambient air, or in other words, one 100th of 1% of the overall mix of gases that make up the air.
- This tiny increase in the already trace levels of CO2 found in the atmosphere, which, if the claim that this puts us on the brink of a “climate emergency” is correct, suggests that temperature is extremely sensitive to additional CO2 above “natural” levels.
- Such sensitivity does not correlate well with the geological temperature record. CO2 concentrations are believed to have been at orders of magnitude higher than they are today without corresponding, runaway temperatures, and conversely, we have seen warmer periods with lower CO2 concentrations.
I hope this article has given you further context to the on-going debate. When you next hear claims of ‘400ppm’, or the earths alleged climate control knob, you will be better equipped to understand these issues and what they REALLY mean!
So, always remain skeptical, ask questions, remind yourself that correlation is not causation, and always be willing to accept new ideas in the face of new evidence.
The scientific method demands it!
-Tristan