And noticed that the entire world was above 400ppm except a small green patch in the middle of Africa.
Which just happens to be the same position that Marvel choose as the location for the fictional Sub-Saharan African nation of Wakanda in the MCU.
On a more serious note, the reason for this is most likely the tropical forest absorbing the CO2. The truly worrying part is the fact that we are now way past the 400ppm threshold, maybe permanently, set by scientists as the point of no return.
A workmate of mine, who actually did climate modelling as part of his PhD, made me aware to also keep an eye on Methane, which is a much more potent green house gas with devastating impact on marine life. It is mainly produced by life stock. The upside about this is that if we stop emitting it will relatively quickly leave the atmosphere.
By the way, atmospheric measurements are just a small part of the Copernicus program.