Which statement describes a direct climate effect of particulate matter?

Which statement describes a direct climate effect of particulate matter?

• A. PM has no climate effect.
• B. PM only affects climate by responding to humidity.
• C. PM scatters and absorbs solar radiation.
• D. PM increases surface albedo by reflecting all radiation.

Answer: (C)

Particulate matter directly interacts with incoming solar radiation by both scattering and absorbing light. When aerosols scatter sunlight, they reduce the amount of solar energy reaching Earth's surface, which tends to cool the surface. When aerosols absorb sunlight, especially dark carbonaceous particles like black carbon, they heat the surrounding air and alter the atmospheric temperature structure. This direct radiative forcing is the direct climate effect. The other ideas aren’t accurate: PM does affect climate, and its influence isn’t limited to humidity-driven changes, and it doesn’t simply reflect all radiation to boost surface albedo. Thus scattering and absorbing solar radiation best describes the direct climate effect.

Particulate matter directly interacts with incoming solar radiation by both scattering and absorbing light. When aerosols scatter sunlight, they reduce the amount of solar energy reaching Earth's surface, which tends to cool the surface. When aerosols absorb sunlight, especially dark carbonaceous particles like black carbon, they heat the surrounding air and alter the atmospheric temperature structure. This direct radiative forcing is the direct climate effect. The other ideas aren’t accurate: PM does affect climate, and its influence isn’t limited to humidity-driven changes, and it doesn’t simply reflect all radiation to boost surface albedo. Thus scattering and absorbing solar radiation best describes the direct climate effect.