What is insulation?

• A. The process of plants absorbing CO2
• B. The process by which the atmosphere retains heat
• C. The ozone layer protecting UV
• D. A method of energy production

Answer: (B)

Insulation is anything that slows the transfer of heat. In the Earth’s climate system, the atmosphere and its greenhouse gases act like insulation by trapping some of the heat that would otherwise escape back to space. When sunlight warms the surface, the ground and water emit infrared radiation. Greenhouse gases such as water vapor, carbon dioxide, and methane absorb a lot of that infrared energy and re-emit it in all directions, including back toward the surface. This trapping keeps the lower atmosphere and surface warmer than they would be otherwise. That’s why the atmosphere retaining heat describes insulation in this context. The other options describe different processes—photosynthesis, the ozone layer’s UV protection, and energy production—not heat retention.