The yearly rise and fall of CO2 levels in the atmosphere are
caused by:
A. seasonal use of fossil fuels
B. regularity of volcanic activity
C. deforestation in the tropics
D. El Nino events
E. seasonal photosynthetic activity of green plants
Seasonal use of fossil fuels, human activities are changing the natural greenhouse. Over the last century the burning fossil fuels like coal and oil has increased carbon dioxide in the atmosphere. Hope this helps!!
