Which concept explains how gases trap heat in the atmosphere, moderating Earth's temperature?

• A. Rain Shadow Effect
• B. Greenhouse Effect
• C. Forced Migration
• D. Urbanization

Answer: (B)

The greenhouse effect explains how certain gases in Earth’s atmosphere trap heat, moderating the planet’s temperature. Sunlight heats the surface, which then radiates infrared heat upward. Greenhouse gases such as water vapor, carbon dioxide, and methane absorb much of that infrared energy and re-radiate it in all directions, including back toward the surface. That trapping keeps the lower atmosphere and surface warmer than they would be otherwise, helping to stabilize a climate that supports life. If these gas concentrations rise, more heat is retained and the average temperature increases.

The other options describe different processes: the rain shadow effect is about mountains causing one side to receive more rainfall than the other; forced migration involves people moving due to environmental or other pressures; urbanization refers to the growth of cities and can influence local temperatures, but it doesn’t describe how atmospheric gases trap heat to regulate Earth's overall temperature.