The existence of seasons in nature derives from the annual cycle of change in the earth's climate, which in turn derives from the geometry of our planet's orbit around the sun. However, seasons exist in a social sense also, as in the season of fasting at Ramadan or Lent. There is little that can be done to reduce seasonality of these types. The earth's climate is a system over which, perhaps mercifully, humankind has little deliberate control as yet. Even when seasonality has its roots in the social and religious traditions of a people, there is often little that can be done to change this – even if it were deemed desirable to do so – except perhaps in the very long term. An understanding of these sources is nevertheless an essential starting point for a study of both the effects of seasonality and ways of tackling the problems it creates.

Climatic sources

SEASONAL TEMPERATURE VARIATION

Temperature is a fundamental element of climate and in many ways its most important: many of the others are directly or indirectly dependent upon it. The earth's temperature is a function of solar radiation (insolation). The amount of solar radiation reaching the upper atmosphere is more or less constant, but its effect on atmospheric temperature is altered by a number of factors. First, the earth's surface is more or less at right angles to the sun's rays in the Equatorial zone, but as latitude increases, the curvature of the earth has the effect of presenting an increasingly angled surface to these rays, so that the same amount of radiation is spread over an increasingly wide area, reducing the intensity of insolation reaching the ground.