Major Gases, Trace Gases, Methane, and Carbonates

Typical exam question

1. If we are worried about emissions of CO2 from fossil fuels, why is so much attention paid to natural sources and sinks of atmospheric CO2?

2. How does a gas qualify as a greenhouse gas?

3. Since water vapor is the most abundant greenhouse gas, why do we not consider eliminating agricultural irrigation rather than limiting CO2 or methane emissions?

4. Discuss the validity of the following statement: "Carbonated beverages (e.g., Coke, Pepsi) give off CO2 and therefore contribute to an increase in greenhouse gases."