Incidentally, while searching for a reference to the assertion that CO2 is and methane is not included in a carbon footprint, I found the opposite:
https://en.m.wikipedia.org/wiki/Carbon_footprint
(Methane emmisions are expressed in terms of the equivalent CO2 effect and added with actual CO2, the unit is then written as CO2e.)
My original quibble is therefore much less important.
