Guest Post by Willis Eschenbach
As a result of my last post looking at the question of CO2 and COVID, I came up with an interesting question, viz:
What is the lag time between changes in CO2 emissions and Mauna Loa measurements of background CO2?
I didn’t realize what a struggle it would be. I started out looking for weekly CO2 emissions data … ho, ho, ho. Now rightly or wrongly, I consider myself a reasonable searcher for data. But finding weekly emissions data turned out to be a dead end.
So I looked for weekly CO2 data. That took a while, but I finally got weekly Mauna Loa data from NOAA here. With that in hand, I went back to looking for the emissions data … still no joy.
I can’t tell you how many blind alleys I went down without finding sweet Fanny Adams. As a result, after giving vent to a cornucopia of bad words at a remarkable volume, I ended up having to digitize the data from this plot from Nature magazine …
Figure 1. Emissions from 2019 and part of 2020. SOURCE
After digitizing the emissions data, I grouped it into weekly data using the same weeks as the Mauna Loa data. Then I used a cross-correlation to figure out how many weeks there were between the emission of the CO2, and the resulting change in the atmospheric CO2.
Here are the results … which did indeed surprise me …
Figure 2. Standardized CO2 emissions and standardized Mauna Loa CO2 concentration data.
Hmmm … now there are a couple of possibilities. One is that the CO2 emissions and atmospheric CO2 each have an independent annual cycle, and each peaks at different times.
The other is that what we’re seeing above is actually the relationship between emissions and atmospheric CO2. The size of the relationship tends to support the latter. Overall, it takes 2.13 Gt of carbon emitted per 1 ppmv increase in atmospheric CO2. The relationship shown above gives a relationship of 3 Gt of carbon per ppmv, certainly within specs. However, that may just be coincidence.
Now here’s another oddity. Without much thinking about it, I’d always accepted the following explanation for the annual cycle of CO2
There’s more carbon dioxide in the winter and a bit less in the summer. That’s the collective breathing of all the plants in the Northern Hemisphere.
“Plants are accumulating carbon in the spring and summer when they’re active, and they’re releasing carbon back to the air in the fall and winter,”
However, looking at my Figure 2 above, I said … whaa? Does that seem like what I see in my figure?
Fearing I’d made a mistake, I went back to the Mauna Loa data. I averaged all of the individual months, and here’s what I got:
Figure 3. Average monthly CO2 anomaly and NH land temperature index
Curious. CO2 peaks in May, and drops after that. Sure doesn’t seem like “Plants are accumulating carbon in the spring and summer when they’re active” to me. Meteorological spring is March through May, and meteorological summer is June through August.
So according to accepted theory, CO2 levels should drop from March through August … but instead they’re dropping starting in May and don’t start rising until October.
And this doesn’t even take into account the ~ 4 month lag between surface changes and airborne changes shown in Figure 2 … if that’s the case, then a drop starting in May in atmospheric CO2 would correspond to a surface CO2 drop starting in February.
But what do I know, I was born yesterday.
Let me be clear that I take no position on all of this other than to call it most interesting.
My best to all. You’ve no doubt heard about the Lunar New Year? …
Well, this is shaping up to be the Looney New Year, so stay well in these parlous times.