Question, is it possible the differences are seasonal. winter solistice daylight is shortest so plants don't convert co2 to oxygen as long while in summer solstice the revers is in effect. However how many people keep real existing as simultaneously taking place into account when living in one time zone as both solstices happen at the same time in this atmosphere. Gee all that convection north and south of the equator and all that energy reverse current flows of expaning and contracting by day and night.
hummmmm. statistics lie and liars promote statistical facts which here is the punchline, facts are designed to confuse where actual existing removes the confusion.