It is the fluxes principally of energy but also of moisture, momentum and mass, which determine the state of our climate. Factors which influence these on a global scale may be regarded as causes of global climate change. So far, however, only the fluxes in and out of and within the atmosphere have been considered. In the introduction, it was highlighted that the atmosphere forms just one, albeit, major component of the climate system. Before looking at the causes of global climate change then, it is worth devoting a little time to the other components of the climate system (the oceans, cryosphere, biosphere and geosphere), and how the fluxes of energy, moisture momentum and mass operate between them.