Compare current CO2 levels to the highest concentrations from the past 450,000 years. Based on these websites, answer the following questions:
What is the current CO2 concentration in parts per million (ppm)?
Is this higher or lower than the highs over the past 450,000 years?
From what three sources do humans add CO2 to the atmosphere?
What two sources take CO2 out of the atmosphere?
How does deforestation contribute to the global warming process?
In your opinion, are humans contributing to global warming, or is it just a natural part of the cycle?