# Why does the southern hemisphere have lower concentrations of CO2?

1. The rate of photosynthesis during spring in the Southern hemisphere is high in locations with large forested areas (more $C {O}_{2}$ consumed and ${O}_{2}$ released).
It is rather complicated on top of the photosynthesis effect it was shown that human activities not only are they causing the overall increase in $C {O}_{2}$ levels over time, but through the effect on global temperatures, people are also controlling $C {O}_{2}$ fluctuation from season to season.