What effect does increased atmospheric CO2 have on Earth's average temperature?

• A. It cools the planet
• B. It has no effect
• C. It can trap heat, leading to warmer temperatures
• D. It dissolves CO2 in oceans

Answer: (C)

Increasing atmospheric CO2 strengthens the greenhouse effect: CO2 is good at absorbing infrared heat that the Earth's surface emits after being warmed by sunlight. When more CO2 is present, a larger portion of that heat is trapped in the lower atmosphere and near the surface, so the average temperature rises. This is why higher CO2 levels lead to a warmer climate.

It wouldn’t cool the planet, and saying there’s no effect isn’t accurate. Dissolving CO2 in oceans is a real process that lowers atmospheric CO2 a bit, but it’s not describing the main impact of atmospheric CO2 on global temperature.