One thing I have learned from studying climate science is to be very careful about how certain things are measured, changes in how they are measured, what the raw measurement data looks like and how that data may be adjusted. This article examines how CO2 levels in the air were historically measured, what those measures were, and how changes in those methods appear to be selected for the purpose of exaggerating those levels. The authors collected data from 1812 using chemical analyses for the amount of CO2 in the air. Those measurements showed that CO2 levels tracked with temperature and that at several times before the current climate hysteria began CO2 levels were quite high, approaching today’s levels, most recently in 1942.
In the mid 20th century scientists started using some other CO2 measurement methods and in recent decades methods that resut in high levels appear to be selectively used and promoted. Those methods are not as accurate as the earlier and still available chemical methods. As usual, the scientists who are either ideologues or who make lots of money by promoting the hysteric narrative have chosen methods and cherrypicked start times to support the bullshit notion that CO2 levels are unprecedently high and rising rapidly and that CO2 controls the Earth’s temperature. The truth appears to be that CO2 levels have often showed large cyclic variation over the last two hundred years, cycles which appear to have little connection to fossil fuel use and which appear connected to rises or falls in temperature. (Sage Article)
You are off base on this one. The old chemical methods were not all that accurate and measurements were often made in areas with a high local CO2 concentration. The measurements made since the 1950’s at Mauna Loa, and over shorter times at other locations, are very carefully done with great attention paid to calibrating against high quality standards. Their accuracy and precision is excellent, allowing one to easily see the seasonal cycles and the variation in those cycles between northern and southern hemispheres. There is a lot wrong with climate science, but contemporary CO2 measurements are not among them.
I think the author is more focused on the ignoring of older measurements which showed high CO2 levels. I doubt that they were systematically erroneous and he seems to have done a very thorough examination of the research. Obviously, those pushing the CO2 story want to ignore any high readings in the past century.