Question

When the levels of greenhouse gases in Earth's atmosphere increase, which statement is true?

Earth's temperature increases because Hin increases.
Earth's temperature increases because Hout increases.
Earth's temperature increases because Hout decreases.
Earth's temperature increases because Hin increases and Hout decreases.

Answer 1

Earth's temperature increases because Hout decreases.

Greenhouse gases absorb and re‑emit outgoing longwave (infrared) radiation, so less heat escapes to space (Hout drops). That creates a net energy surplus which warms the planet until outgoing emission rises again at the higher temperature. Incoming solar (Hin) is essentially unchanged.