Temperature changes the PH and has a direct effect on the CSI. The two effects happen to more or less cancel out, the indirect change of the CSI from the PH shift is opposite to the direct effect on the CSI. Unless you are holding the PH steady, relatively unlikely at low temperatures, you don't normally need to worry about it.
There are many small effects like that. Thinking about them can be entertaining for some people, but normally there is no need to know anything about them.