Climate is the sum of all weather
events affecting a locale. Climatologists use statistical measures
such as means (or 30-year "normals") and extremes to
describe a location's climate and proxy data to extend the record
into times and places where data are not available. Many factors influence a locale's
climate. Chief among them are latitude, altitude, location with
respect to oceans or mountains, local topographic and surface
conditions, global winds and ocean currents, and anthropogenic
effects. Climate classification schemes are
of two main types: genetic, based on causative factors, and empirical,
based on climate data. According to the empirical system
of Köppen and others (Table 13.2 and Figure 13.10), the world's
climates fall into six broad categories. The divisions are based
on differences in monthly and annual means of temperature and
precipitation. Climates of type A are found at and near the equator;
climates B, C, D, and E typically occur at successively higher
latitudes. The sixth type, labeled H (for highlands), comprises
high altitude climates. The six basic types are subdivided according
to specifics of monthly mean moisture and temperature data. It is known that astronomical, geological,
oceanic, and anthropogenic factors are likely to have caused or
to be causing perturbations in earth's climate. It is also known
that in the past, the climate has exhibited instability, changing
abruptly from one regime to another. However, in general, we do
not know whether a given perturbation will cause the atmosphere
to respond in a stable, unstable, or neutral fashion. Much research
is in progress on various aspects of this important problem.
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