If they rise in spring and summer in the northern hemisphere then they fall during spring and summer in the southern hemisphere since fall and winter in the southern hemisphere happen at the same time as spring and summer in the northern hemisphere. LOL
That means the northern hemisphere dominates carbon dioxide levels. We can figure out why by watching birds. Migratory birds migrate to the north from the south during spring and spend the summer up north. The reason they do that is because days are long during spring and summer up north, and the longer days provide plants with the light they need for growth. :Plant eaters have more to eat, and predators also have more food because they can eat the plant eaters. Because plants release oxygen and absorb carbon dioxide during photosynthesis, the longer days allow plants to photosynthesize longer and release more oxygen while absorbing carbon dioxide. At night plants release carbon dioxide, and the shorter nights means they release less of that.
If that is the case, why don't birds fly south to take advantage of the longer winters in the southern hemisphere. the reason is that Antarctica is frozen year round, and South America and South Africa are not close enough to the south pole to allow plants growing there to experience long summer days. Besides, the tips of South America and southern Africa are tiny compared to land further up north close to the Equator. In contrast there is a lot of land up near the North Pole. That further reduces the amount of land that plants can occupy to experience a long summer near Antarctica. As a result, photosynthesis during the summer and spring does not equal the same seasons in the north. Meanwhile up north photosynphetic activity is slowed due to shorter days and colder temperatures. Many annual plants may also become dormant or drop all their leaves. And that is why we see higher levels of carbon dioxide from October to March every year.