Which statement best describes the relationship between a planet’s atmosphere and its surface temperature in the context of climate?

Which statement best describes the relationship between a planet’s atmosphere and its surface temperature in the context of climate?

• A. A thinner atmosphere always leads to higher temperatures.
• B. The atmosphere has no effect on surface temperature.
• C. A thicker atmosphere with greenhouse gases tends to raise surface temperature.
• D. Surface temperature depends only on the star’s brightness, not the atmosphere.

Answer: (C)

Think of the planet’s surface temperature as a balance between heat coming in from the star and heat escaping back to space. The atmosphere acts like a blanket. Greenhouse gases in the air absorb infrared radiation emitted by the warmed surface and then re-radiate it in all directions, including back toward the surface. A thicker atmosphere with more greenhouse gases means more heat is trapped, so more of the Sun’s warmth stays near the surface, raising the average surface temperature. That’s why planets with thick, gas-rich atmospheres tend to be warmer than those with thin atmospheres, all else being equal. Of course, the exact temperature also depends on how much sunlight the planet receives and how reflective its surface is, but the greenhouse effect is a primary driver of surface warmth.

Think of the planet’s surface temperature as a balance between heat coming in from the star and heat escaping back to space. The atmosphere acts like a blanket. Greenhouse gases in the air absorb infrared radiation emitted by the warmed surface and then re-radiate it in all directions, including back toward the surface. A thicker atmosphere with more greenhouse gases means more heat is trapped, so more of the Sun’s warmth stays near the surface, raising the average surface temperature. That’s why planets with thick, gas-rich atmospheres tend to be warmer than those with thin atmospheres, all else being equal. Of course, the exact temperature also depends on how much sunlight the planet receives and how reflective its surface is, but the greenhouse effect is a primary driver of surface warmth.