CO2 levels on Earth don't drop nor rise.
Rather the CO2 just moves from 1 place to another. From the atmosphere to the Earth's mantle via subduction, for example.
& the movement of any significant amount of CO2 cannot be achieved with any technology present on Earth.
Currently, only nature can do this.
For example, here is a true account of what caused CO2 to be pulled out of Earth's atmosphere & deposited into rocks:
When the Himalayan Mountains were formed, they changed the weather around them so that it rained more often.
This excessive rain pulled CO2 out of the atmosphere. We call this acid rain. The CO2 was deposited & trapped in the rock of the mountain range.
Then the excessive decline of CO2 in the atmosphere triggered the start of the last Ice Age.
Techtonic activity formed the Himalayas.
The Himalayas caused excessive rain.
The excessive rain pulled CO2 from the atmosphere & in the rock of the Himalayas.
The transfer of the CO2 started the Ice Age.
-This kind of affect cannot be done by people because there exists no means for us to bring this about....certainly not in a mere 8 years!
obama has not done any more for the Earth's environment than you & I have.
If anything, you & I have done more good for the Earth than obama, just because he flys a fossil fuel jet all the time; & you & I don't.