What is albedo and how does it influence climate?

• A. Albedo is atmospheric gas concentration; higher albedo increases greenhouse effect.
• B. Albedo is cloud cover; increases warming.
• C. Albedo is ocean salinity; changes sea level.
• D. Albedo is surface reflectivity; high albedo reflects more solar radiation, cooling; low albedo absorbs heat, warming.

Answer: (D)

Albedo is the reflectivity of a surface—the fraction of incoming solar radiation that is bounced back into space. A high albedo means more sunlight is reflected and less is absorbed, which tends to cool the surface and surrounding air. Snow, ice, and light-colored surfaces have high albedo, while dark surfaces like forests, oceans, or bare soil have low albedo and absorb more heat, leading to warming. This energy balance is central to climate, and changes in surface cover can shift regional and even global temperatures. A key example is the ice-albedo feedback: as ice melts and exposes darker land or ocean, the area absorbs more heat, accelerating warming. The other options mix up what albedo describes—albedo isn’t about atmospheric gas concentrations, cloud cover itself, or salinity—so the definition focused on surface reflectivity best explains its influence on climate.