Climate
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 â€" 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.[
1]
In the most succinct words, weather is the combination of events in the atmosphere and climate is the overall accumulated weather in a certain location.
The exact boundaries of what is climate and what is
weather are not well defined and depend on the application. For example, in some senses an individual
El Niño event could be considered climate; in others, as weather.
When the original conception of climate as a long-term average came to be considered, perhaps towards the end of the 19th century, the idea of
climate change was not current, and a 30 year average seemed reasonable (
note 1). Given the current availability of data on long-term trends in the
temperature record, it is harder to give a definition of climate to suit all purposes: over a 30 year period, averages may shift; over a shorter period, the statistics are less stable.
In a given geographical region, the climate generally does not vary over time on the scale of a human life span. However, over
geological time, climate can vary considerably for a given place on the Earth. For example,
Scandinavia has been through a number of
ice ages over hundreds of thousands of years (the last one ending about 10,000 years ago).
Paleoclimatology is the study of these past climates, their origin, and by extension, the origin of today's climate.
In the original
Greek sense,
'Clime,' was a concept used to divide the world into regions sharing similar climatic attributes, such as temperature and length of the solar day (sunlight), and in particular
latitudinal distance from the
equator into a so called
climatic zone. The more common modern equivalent and
technically accepted term is
climate regions, since latitudinal concepts of antiquity don't hold up well against modern science data and analysis, which show climate is a much more localized phenomenon affected by the presence of geographical features such as local
hills or
mountain ranges, large
lakes, broad
plains,
forests or their lack, and
seas or
oceans, et cetera. Other factors are listed in the table following:
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 AntarcticaFor the climate of a specific place or area, see the article on that place or area.
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.
 |
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*
Climate change*
Solar variation*
Temperature extreme*
Climateprediction.net - a
distributed computing project (using, amongst others,
BOINC) to try and produce a
forecast of the climate in the 21st century
Website*
Biome - an
ecological term for a major regional group of distinctive plant and animal communities best adapted to the region's physical environment
*
Effect of sun angle on climate*
Climate changes of 535-536*
Medieval climate optimum*
Climate of the Alps*
Climate of India*
Climate of the United Kingdom*
Climate Prediction Project*
WorldClimate*
ESPERE Climate Encyclopaedia*
Extreme Temperatures Around the World-Historical Records*
Weatherbase*
Global Climate Data*
The Climate of Peru*
Climate index and mode information*
Why and how do scientists study climate change in the Arctic? What are the Arctic climate indices?*
A near-realtime Arctic Change Indicator Website*
A current view of the Bering Sea Ecosystem and Climate*
Weather Source. An excellent resource for historical weather observations.# In "Climatology" by W G Kendrew (OUP; 3rd edition 1949; chapter 38; page 359) we find: "A well-known cycle is one with a mean period of about 35 years... which was worked out by Bruckner... the reality of this cycle seems to be well established, though it is of little use for actual forecasting; it is a basis of the choice of 35 years as the period estimated to give true mean values of climate elements."
