Solar Irradiance

Varies from 1365.5 W/m² to 1366.5 W/m² over the solar cycle. Average 1366 W/m² - divide by 4 to estimate average on entire geoid. According to Earth's Climate (Ruddiman 2001) page 20, 47% of incoming visible and infrared light is absorbed by the surface (642.02/4 = 161 W/m²) and 4% (14 W/m²) is reflected. Earth surface area (4πR²) is 5.10072e14 m², facing sun (πR²) is 1.27518e14 m², with 51% of the light or 88,840 TW reaching the surface.