Only approximately __% of insolation reaches the earth's surface.

• A. 45%
• B. 50%
• C. 60%
• D. 52%

Answer: (D)

The amount of solar energy that reaches the Earth's surface is reduced by the atmosphere through reflection, scattering, and absorption. Clouds, atmospheric gases, and aerosols take a sizable share of insolation before it gets to the ground, so only about half makes it through on average. About 52% is a commonly cited global average, so that choice reflects typical conditions and rounding. If skies are clearer and there are fewer absorbers, a bit more energy can reach the surface; in more cloudy or polluted conditions, less does. The higher 60% would imply far less atmospheric loss than usually occurs, while 45% is a bit lower than the typical average.