Guest contribution by Willis Eschenbach
I've read comments from several people who claim that despite the COVID lockdowns, which are reducing emissions, the CO2 in the air has not decreased accordingly. Here is a typical graphed claim that shows that human emissions are not causing the gradual increase in CO2 in the air.
The COVID shutdown reduced human CO2 emissions by around 20%. However, the growth of CO2 in the atmosphere at that time was almost the same as in previous years.
What hasn't changed were natural emissions. So much for Willis & # 39; (proverb) "It is man-made" and established science.
Hmmm … everyone who knows me knows I'm a data guy. So I thought I'd look into the situation. I think year-to-year comparison would be far more valuable than the more general graph above. A year-on-year comparison is a graph that shows for each month in the record how much the CO2 content has increased compared to the previous month in the previous year. If we want to understand changes in CO2, we need to look at changes in CO2, not the absolute values that the commentator used above. The CO2 in the air is growing at about 2.5 ppmv per year or so. Figure 1 shows current data that describes in detail the growth in CO2 in the air compared to the previous year.
Figure 1. Year-over-year analysis of CO2 in the air. Each data point shows how much the CO2 in the air increased in the same month last year. Units are parts per million by volume (ppmv). The data comes from the CO2 station on Mauna Loa Mountain on the Big Island. The photo shows Mauna Kea in Hawaii, the other big mountain on the Big Island.
Hmmm … didn't really expect the variation to be that big. The big peak in the middle is from El Nino / La Nina from 2015-2016. The high point and drop off at the start when dated Nino / Nina from 2009-2010. What causes the other variations is far from clear. What is clear is that the values vary from smallest to largest by no less than four hundred percent, from an annual increase of less than one part by volume per million (ppmv) to an increase of over four ppmv … a great natural variation.
Next we need to ask the question that the commenter quoted above did not ask – how much would we expect the CO2 to change due to the lockdowns?
Well, the author of the comment above says emissions were down 20% in 2020 … but that makes my Bad Number Detector ring. In general, carbon emissions for the globe and the resulting changes in global atmospheric CO2 levels are a linear function of global gross domestic product (GDP). GDP is the sum of all goods and services produced during the year.
And as expected, if we increase the quantity of our products, we will increase the CO2 emissions accordingly. (For the math inclined, global annual carbon emissions ≈ 6.3 Gtonnes + 0.4 * global GDP (trillion constant 2010 $).
When I look around the internet, I see estimates for the lockdown-induced drop in GDP in 2020 from 4.5% to 5.3%. And since emissions and the resulting atmospheric values are a linear function of GDP, this would mean that the CO2 increase should be about five percent less than in the previous year.
In this way we can calculate how much the increase in CO2 would have been had there been no closings. Beyond 2020 you would expect that CO2 emissions and the resulting annual CO2 increase in the air would have been 5% higher if there had been no closures.
To be very conservative in our estimate, let's assume that the lockdowns actually doubled emissions, or 10%. If we use ten percent as our number, our results will be solid.
So … what would the graph above in Figure 1 look like without this 10% drop in emissions in 2020? Figure 2 shows this result. Also, for the sake of interest, I added what a 20% emissions difference would look like. This is four times the actual ~ 5% change expected due to the GDP decline.
Of course there will be no change until 2020 …
Figure 2. As in Figure 1, but with lines added showing a 10% (yellow) and 20% (orange) increase in CO2 emissions without blocking.
Again … hmmm. I have to say that in a system of these variables a difference of 10% or even 20% is indistinguishable from the background. I mean, each of those three lines is absolutely believable.
My main conclusion is that despite the enormous, almost incalculable human cost of the barriers, the change in the rate of CO2 rise is lost in noise … which certainly does not say anything about whether the rise is man-made.
My other conclusion is that this should give a big break for those who cheerfully recommend completely restructuring the world economy to replace fossil fuels. Look at the real cost of the barriers around you and see the meaningless carbon benefits in the graph above. Not worth it on any planet.
My best wishes to everyone in this most curious year 2020 cannot be over soon enough for me.
PS: For those who are wondering about a CO2 observatory on the side of an outgassing volcano, see my post Below the volcano, above the volcano.
PPS – When leaving a comment please include the exact words you are talking about. I can defend my own words. I cannot defend your interpretation of my words.