ABSTRACT
The general circulation of the atmosphere and oceans is the mechanism of climate. The heat and energy of the system is supplied by the sun in quantities graded according to latitude and season. It may be surmised that the sun is to some extent a variable star, though it has not been possible to establish any measurable variation of solar energy over the few decades since pyrheliometric measurements at mountain observatories began. 41 , 73 The rôle of geography is to modify—within limits—the distribution of heat input, through the different responses of land, sea and ice to incoming radiation and through the mobile reserves of heat stored in the oceans, as well as to channel and constrain the free flow of the winds. The actual braking effect upon the atmosphere is most important at great mountain barriers, especially those arrayed north and south across the mainstreams of the atmospheric circulation.
