Which percentage of insolation reaches Earth's surface?

• A. 60%
• B. 70%
• C. 52%
• D. 40%

Answer: (C)

The amount of insolation that reaches the surface is what gets through the atmosphere after you account for reflection and absorption there. The atmosphere and clouds don’t pass all the Sun’s energy to the ground; a portion is reflected back to space and a portion is absorbed or scattered within the air. When averaged across the globe, about half of the incoming solar radiation makes it to the surface, and 52% is a commonly used representative figure for that global mean. This value sits between higher and lower extremes and reflects typical cloudiness, aerosols, and atmospheric composition. Regional conditions—like clear skies versus heavy cloud cover, or different latitudes—can shift the actual percentage, but 52% gives a solid average idea of how much solar energy warms the surface.