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.
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Well, both latitude and intensity of light affect temperature because, the higher the light intensity, the higher the temperature and since latitude is the measure of how close you are to the equator, then the closer to the equator you are, the higher the temperature is.