CLIMATE WATCH - The Keeling Curve - keeping track of atmospheric CO2
Back in the 1950s, Charles Keeling took up a suggestion from his supervisor that it would be an interesting project for his PhD in chemistry to develop a way of measuring atmospheric CO2 concentration very accurately ...... he had no idea that he would find it rising year on year.
Why the wiggle? The Keeling Curve has an annual cycle.
Every year there is a decline in CO2 during months of terrestrial plant photosynthesis (basically northern summer) and an increase in CO2 in months without large amounts of photosynthesis and with significant decomposition - in both cases, it relates to the northern hemisphere, where there are more forests.
https://keelingcurve.ucsd.edu/
https://celebrating200years.noaa.gov/datasets/mauna/welcome.html#1958