Consider the Keeling curve, which shows a steady increase in CO₂ levels over the past 50+ years. This steady rise has been attributed to both natural and human activity. Imagine if everyone in the world planted a fast-growing vine that was an annual (i. e., it grows large and fast, but dies after one year). Predict the effect this would hypothetically have on the level of CO₂ in the atmosphere over the next 20 years.
a. The level of CO₂ in the atmosphere will stay the same because the growing annuals will remove the extra CO₂ from human activity.
b. The level of CO₂ in the atmosphere will steadily decrease because of increased rates of photosynthesis.
c. The level of CO₂ in the atmosphere will steadily increase because decomposition of the annuals simply returns the CO₂ back into the atmosphere.