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Climate

2007 Schools Wikipedia Selection. Related subjects: General Geography

   The Earth, as seen from Apollo 17.
   Enlarge
   The Earth, as seen from Apollo 17.

   The climate (from ancient Greek: κλίμα, " clime") is commonly
   considered to be the weather averaged over a long period of time,
   typically 30 years. Somewhat more precisely, the concept of "climate"
   also includes the statistics of the weather — such as the degree of
   day-to-day or year-to-year variation expected. The Intergovernmental
   Panel on Climate Change(IPCC) glossary definition is:

          Climate in a narrow sense is usually defined as the “average
          weather”, or more rigorously, as the statistical description in
          terms of the mean and variability of relevant quantities over a
          period of time ranging from months to thousands or millions of
          years. The classical period is 30 years, as defined by the World
          Meteorological Organization (WMO). These quantities are most
          often surface variables such as temperature, precipitation, and
          wind. Climate in a wider sense is the state, including a
          statistical description, of the climate system.

                         Atmospheric sciences [cat.]
                                                 Meteorology [cat.]

           weather [cat.]
           tropical cyclones [cat.]

                                                 Climatology [cat.]

           climate [cat.]
           climate change [cat.]
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             Portal Atmospheric Sciences
             Portal Weather

Classifications

   In the original Greek sense, ' Clime,' was a concept used to divide the
   world into climatic zones sharing similar climatic attributes such as
   temperature, length of the solar day (sunlight), and in particular
   latitudinal distance from the equator. Modern data and analysis show
   that the latitudinal concepts of antiquity are too simplistic. Instead,
   the latitudinal trend is altered by such features as hills or mountain
   ranges, large lakes, and seas or oceans.

                     Meteorological data and variables

   Atmospheric pressure | CAPE | CIN | Dew point | Heat index | Humidex |
    Humidity | Pot T | Sea surface temperature | Temperature | Theta-e |
                     Visibility | Vorticity | Wind chill

   Consequently, today's climate regions are classified on the basis of
   temperature and precipitation alone. Examples of such climate schemes
   are the Köppen climate classification and the Thornthwaite climate
   classification. In broad terms, climate zones range in latitude from
   tropical (hot, no real seasons based on temperature) to mid-latitude
   (moderate; conventional winter-spring-summer-autumn seasons) to polar
   (cold; strong seasonality; long winters). They also divide into
   Continental (high contrast between summer and winter) and Maritime
   (ocean influence moderates temperature extremes, but generally
   contribute extra moisture to local weather patterns). The mid-latitude
   'conventional four seasons' only work well in the mid-latitudes. In
   other regions, the more useful divide is into "wet" and "dry" seasons
   based on the monsoon.

   For more details about specific climates, see

     * Tropical climate
     * Subtropical climate
     * Arid climate
     * Semiarid climate
     * Mediterranean climate
     * Temperate climate
     * Oceanic climate
     * Continental climate
     * Alpine climate
     * Subarctic climate
     * Polar climate
     * Climate of Antarctica

   For the climate of a specific place or area, see the article on that
   place or area.

Climate determinants

   Over historic time spans there are a number of static variables that
   determine climate, including: latitude, altitude, proportion of land to
   water, and proximity to oceans and mountains. Other climate
   determinants are more dynamic: The thermohaline circulation of the
   ocean distributes heat energy between the equatorial and polar regions;
   other ocean currents do the same between land and water on a more
   regional scale. Degree of vegetation coverage affects solar heat
   absorption, water retention, and rainfall on a regional level.
   Alterations in the quantity of atmospheric greenhouse gases determines
   the amount of solar energy retained by the planet, leading to global
   warming or global cooling. The variables which determine climate are
   numerous and the interactions complex, but there is general agreement
   that the broad outlines are understood, at least in so far as the
   determinants of historical climate change are concerned.

Climate indices

   Instrumental temperature record of the last 150 years
   Enlarge
   Instrumental temperature record of the last 150 years

   Scientists use climate indices in their attempt to characterize and
   understand the various climate mechanisms that culminate in our daily
   weather. Much in the way the Dow Jones Industrial Average, which is
   based on the stock prices of 30 companies, is used to represent the
   fluctuations in the stock market as a whole, climate indices are used
   to represent the essential elements of climate. Climate indices are
   generally identified or devised with the twin objectives of simplicity
   and completeness, and each typically represents the status and timing
   of the climate factor it represents. By their very nature, indices are
   simple, and combine many details into a generalized, overall
   description of the atmosphere or ocean which can be used to
   characterize the factors which impact the global climate system.
   Because the climate indices are generally determined from measurements
   made in a localized area, they can have impacts in other areas around
   the globe, through processes sometimes called teleconnections.

   References:
     * Why and how do scientists study climate change in the Arctic? What
       are the Arctic climate indices?
     * Climate index and mode information

   Retrieved from " http://en.wikipedia.org/wiki/Climate"
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   with only minor checks and changes (see www.wikipedia.org for details
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