Gas trapping heat in Earth's atmosphere is caused by what?

• A. Ozone
• B. Greenhouse gas
• C. Methane
• D. Carbon dioxide

Answer: (B)

The main concept is the greenhouse effect: certain gases in Earth's atmosphere trap heat. These greenhouse gases are good at absorbing infrared radiation emitted by the planet after it’s warmed by sunlight. When they absorb that infrared energy, they re-emit it in all directions, including back toward the surface, which slows heat loss and keeps the lower atmosphere warmer. That’s why the general category of greenhouse gases is what causes the heat-trapping effect. While gases like carbon dioxide and methane are examples, the mechanism relies on the class of greenhouse gases as a whole. Ozone can absorb heat too, but it isn’t the primary driver of the overall warming, and methane or carbon dioxide are specific members of the same group.