Without the greenhouse effect, the average global temperature would be _____.

Without the greenhouse effect, the average global temperature would be _____.

• A. 0°C (32°F)
• B. 20°C (68°F)
• C. 15°C (59°F)
• D. -5°C (-23°F)

Answer: (A)

The idea being tested is how the greenhouse effect affects Earth's average surface temperature. Greenhouse gases trap infrared heat that would otherwise escape to space, acting like a blanket that keeps the surface warmer. If those gases were removed, the planet would lose that additional warming, so the average temperature would drop by a large amount. The widely cited scientific estimate for the average surface temperature without any greenhouse warming is about -18°C, which is far below freezing. Some classroom-style figures round or simplify this to around 0°C to emphasize the cooling, but the real change is substantial—a drop of tens of degrees. The key point is that removing the greenhouse effect cools the planet significantly, not just a little.

The idea being tested is how the greenhouse effect affects Earth's average surface temperature. Greenhouse gases trap infrared heat that would otherwise escape to space, acting like a blanket that keeps the surface warmer. If those gases were removed, the planet would lose that additional warming, so the average temperature would drop by a large amount. The widely cited scientific estimate for the average surface temperature without any greenhouse warming is about -18°C, which is far below freezing. Some classroom-style figures round or simplify this to around 0°C to emphasize the cooling, but the real change is substantial—a drop of tens of degrees. The key point is that removing the greenhouse effect cools the planet significantly, not just a little.