The zonally averaged radiative balance on Earth
The annual mean, average around latitude circles, of
the balance between the solar radiation absorbed at the ground (in
blue) and the outgoing infrared radiation from Earth into space (in
red). The two curves must balance completely over the entire globe,
but not at every single latitude. In the tropics, there is an access
of radiation (solar radiation absorbed acceeds outgoing terrastrial
radiation) in middle and high latitudes all the way to the poles,
there is a deficit (Earth is radiating into space more than it receives
from the sun). The atmosphere and ocean systems are forced to move about
by this imbalance, and bring heat by convection and advection
from equator to the poles.