The greenhouse effect is a process by which thermal radiation
from a planetary surface is absorbed by atmospheric greenhouse
gases, and is re-radiated in all directions. Since part of this
re-radiation is back towards the surface and the lower
atmosphere, it results in an elevation of the average surface
temperature above what it would be in the absence of the gases.
Solar radiation at the frequencies of visible light largely
passes through the atmosphere to warm the planetary surface,
which then emits this energy at the lower frequencies of
infrared thermal radiation. Infrared radiation is absorbed by
greenhouse gases, which in turn re-radiate much of the energy to
the surface and lower atmosphere. The mechanism is named after
the effect of solar radiation passing through glass and warming
a greenhouse, but the way it retains heat is fundamentally
different as a greenhouse works by reducing airflow, isolating
the warm air inside the structure so that heat is not lost by
convection. If an ideal thermally cond