The Greenhouse Effect

A portion of the sunlight
penetrates through the clouds and atmosphere of Venus, heating
its surface. The surface in turn emits infrared radiation,
much of which is absorbed by carbon dioxide (and to a much
lesser degree, water vapor). The trapped radiation helps
increase the average temperatures of the surface and atmosphere.
Some infrared radiation does penetrate the atmosphere
and leaks into space. In a state of equilibrium, the rate at which
the planet loses energy to space in this way is equal to the rate
at which it absorbs energy from the Sun