Guest Post by Willis Eschenbach
For the usual totally obscure reasons, I got to thinking about the increase in atmospheric CO2. I thought I’d compare it with population growth. Here’s that graph.
Figure 1. Atmospheric CO2 levels, and population growth, 1800 – 2020
When I looked at that graph, I noticed that the CO2 rose in general agreement with the population growth, but with a delay. Now, this made perfect sense to me. The population increases when a baby is born … but the baby doesn’t get involved in CO2-producing activities until the baby is an adult.
So I decided to see if I could use the standard formula for lagging and resizing that I used in my recent post about CO2, “Feeling The Bern“, to see if the CO2 levels could be emulated using just the population growth. Here’s the result of that calculation.
Figure 2. Atmospheric CO2 levels as calculated as a lagged and resized version of the population growth.
There are a few interesting points about this result. First, the fit is remarkably good. The residual standard error, which is the average difference between the calculated value and the actual CO2 level, is only one ppmv. That’s about a third of one percent error … very small.
Next, the half-life of the calculation is 30 years, a reasonable value for a child growing up and becoming involved in CO2-producing activities.
Next, over the last 170 years, there’s been no change in lambda, the amount of atmospheric CO2 increase per each additional billion people …
Having seen all of that, I got to thinking about the future. Here’s the UN population projection. They say that the population is likely to peak at around 11 billion people in the year 2100.
Figure 3. UN population projection to 2100.
So … assuming the population stays level at the 2100 level until 2200, and other things remain constant, two assumptions that are rarely true … here’s the CO2 projection out to the year 2200.
Figure 4. CO2 projection to 2200, using the method of Figure 2 with the same tau and lambda values.
And to complete the circle, here are temperature projections based on that estimate of future CO2 changes.
Figure 5. Past and future temperature anomalies based on the CO2 projections in Figure 4. Please be clear that I do not think that global average surface temperature is a function of CO2 levels, so this is done purely as a theoretical exercise.
And at the end of all of that, I’m reminded of Mark Twain’s comment regarding the length of the Mississippi River.
The Mississippi between Cairo and New Orleans was twelve hundred and fifteen miles long one hundred and seventy-six years ago. Its length is only nine hundred and seventy-three miles at present.
In the space of one hundred and seventy-six years the Lower Mississippi has shortened itself two hundred and forty-two miles. That is an average of a trifle over one mile and a third per year. Therefore, any calm person, who is not blind or idiotic, can see that in the Old Oolitic Silurian Period, just a million years ago next November, the Lower Mississippi River was upwards of one million three hundred thousand miles long, and stuck out over the Gulf of Mexico like a fishing-rod.
And by the same token any person can see that seven hundred and forty-two years from now the Lower Mississippi will be only a mile and three-quarters long, and Cairo and New Orleans will have joined their streets together, and be plodding comfortably along under a single mayor and a mutual board of aldermen.
There is something fascinating about science. One gets such wholesale returns of conjecture out of such a trifling investment of fact.
Now, back to pressure-washing …
Como De Costumbre: I can defend what I write. I choose my own words very carefully, and I’m often asked and always prepared to defend them. However, I can’t defend someone else’s interpretation of my words … so please, when you comment, quote the exact words you are referring to.