Figure — Details of Earth's energy balance (source: Kiehl and Trenberth, 1997). Numbers are in watts per square meter of Earth's surface, and some may be uncertain by as much as 20%. The greenhouse effect is associated with the absorption and reradiation of energy by atmospheric greenhouse gases and particles, resulting in a downward flux of infrared radiation from the atmosphere to the surface (back radiation) and therefore in a higher surface temperature. Note that the total rate at which energy leaves Earth (107 W/m² of reflected sunlight plus 235 W/m² of infrared [long-wave] radiation) is equal to the 342 W/m² of incident sunlight. Thus Earth is in approximate energy balance in this analysis.