Which components absorb insolation not reaching the surface?

• A. Ozone
• B. Oxygen
• C. Water vapour, dust, clouds
• D. Nitrogen

Answer: (C)

Solar radiation that would otherwise reach the surface is reduced as it passes through the atmosphere because certain components absorb or scatter it. The combination of water vapour, dust particles, and clouds performs this role across a broad range of wavelengths, absorbing and reflecting a substantial portion of insolation before it can reach the ground. Oxygen and nitrogen are largely transparent to much of the solar spectrum, so they don’t significantly cut the amount of insolation arriving at the surface. Ozone does absorb ultraviolet radiation, but that absorption targets UV largely high up in the atmosphere, not across the full range of insolation that affects surface heating. So, the way water vapour, dust, and clouds diminish insolation reaching the surface best captures the concept.