This book provides a comprehensive presentation of Earth's energy flows
and their consequences for the climate. The Earth's climate as well as
planetary climates in general, are broadly controlled by three
fundamental parameters: the solar irradiance, the planetary albedo and
the planetary emissivity. Space measurements indicate that these three
quantities are remarkably stable. A minor decrease in planetary
emissivity is consistent with theoretical calculations. This is due to
the ongoing increase of atmospheric greenhouse gases making the
atmosphere more opaque to long wave terrestrial radiation. As a
consequence radiation processes are slightly out of balance as less heat
is leaving the Earth in the form of thermal radiation than the incoming
amount of heat from the sun. Present space-based systems cannot yet
satisfactorily measure this imbalance, but the effect can be inferred
from the measurements of the increase of heat in the oceans. Minor
amounts of heat are also used to melt ice and to warm the atmosphere and
the surface of the Earth.
The book brings to fore the complexity of feedback processes of the
Earth's climate system and in particular the way clouds and aerosols
affect the energy balance both directly and indirectly through feed-back
loops driven by the dynamics of atmospheric, ocean and land surface
processes. The book highlights recent scientific progress as well as
remaining challenges.
Previously published in Surveys in Geophysics, Volume 33, Nos. 3-4, 2012
