Which gas is most directly emitted by burning fossil fuels and is a major driver of anthropogenic climate forcing?

• A. Carbon dioxide
• B. Nitrogen
• C. Oxygen
• D. Argon

Answer: (A)

When fossil fuels burn, the carbon contained in the fuel reacts with oxygen in the air to form carbon dioxide. This gas is a greenhouse gas that traps heat in the atmosphere, and it accumulates over time, giving it a long-lasting influence on Earth's climate. Because of both the large amounts released and its lasting presence, carbon dioxide is the primary driver of anthropogenic climate forcing from burning fossil fuels.

Nitrogen and Argon are already common in air and are not produced in large quantities by combustion; burning primarily consumes oxygen rather than producing it. Oxygen itself isn’t released as a major combustion product. So these gases aren’t the main emissions driving climate change.