= Solar Irradiance =

Varies from 1365.5 W/m² to 1366.5 W/m² over the [[ https://en.wikipedia.org/wiki/Solar_cycle#Surface_magnetism | 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.