Why were levels of CO2 much higher in the atmosphere millions of years ago?

CO2 levels are determined by the imbalance between carbon sequestration (burial in sediments, capture by plants), and carbon emissions (rock weathering and volcanic activity). Imbalances in this system created a downward trend in CO2 levels, leading to a glaciation period around 300 million years ago.

Explanation:

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the sun's light combined with the visible wavelenghts form what is called ultraviolet radiation, which are the long waves at the end of a visible light sprectrum.

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