HOME
TheInfoList



Climate is the long-term average of weather, typically averaged over a period of 30 years. More rigorously, it is the mean and variability of meteorological variables over a time spanning from months to millions of years. Some of the
meteorological Meteorology is a branch of the atmospheric sciences which includes atmospheric chemistry and atmospheric physics, with a major focus on weather forecasting. The study of meteorology dates back millennia, though significant progress in meteorolo ...
variables that are commonly measured are
temperature Temperature is a physical quantity that expresses hot and cold. It is the manifestation of thermal energy, present in all matter, which is the source of the occurrence of heat, a flow of energy, when a body is in contact with another that is ...
,
humidity Humidity is the concentration of water vapor present in the air. Water vapor, the gaseous state of water, is generally invisible to the human eye. Humidity indicates the likelihood for precipitation, dew, or fog to be present. Humidity depends o ...

humidity
,
atmospheric pressure Atmospheric pressure, also known as barometric pressure (after the barometer), is the pressure within the atmosphere of Earth. The standard atmosphere (symbol: atm) is a unit of pressure defined as , which is equivalent to 760mm Hg, 29.9212inchesH ...
,
wind Wind is the flow of gases on a large scale. On the surface of the Earth, wind consists of the bulk movement of air. Winds are commonly classified by their spatial scale, their speed, the types of forces that cause them, the regions in which they ...
, and
precipitation In meteorology, precipitation is any product of the condensation of atmospheric water vapor that falls under gravitational pull from clouds. The main forms of precipitation include drizzling, rain, sleet, snow, ice pellets, graupel and hail. ...

precipitation
. In a broader sense, climate is the state of the components of the
climate system Earth's climate arises from the interaction of five major climate system components: the atmosphere (air), the hydrosphere (water), the cryosphere (ice and permafrost), the lithosphere (earth's upper rocky layer) and the biosphere (living things). ...
, which includes the ocean and ice on Earth. The climate of a location is affected by its
latitude In geography, latitude is a geographic coordinate that specifies the north–south position of a point on the Earth's surface. Latitude is an angle (defined below) which ranges from 0° at the Equator to 90° (North or South) at the poles. Lines ...
,
terrain Relief map of Sierra Nevada, Spain Terrain or relief (also topographical relief) involves the vertical and horizontal dimensions of land surface. The term bathymetry is used to describe underwater relief, while hypsometry studies terrain rel ...

terrain
, and
altitude Altitude or height (also sometimes known as depth) is a distance measurement, usually in the vertical or "up" direction, between a reference datum and a point or object. The exact definition and reference datum varies according to the context ( ...
, as well as nearby
water bodies (Lysefjord) in Norway A body of water or waterbody (often spelled water body) is any significant accumulation of water, generally on a planet's surface. The term most often refers to oceans, seas, and lakes, but it includes smaller pools of wate ...
and their currents. Climates can be classified according to the average and the typical ranges of different variables, most commonly temperature and precipitation. The most commonly used classification scheme was the
Köppen climate classification The Köppen climate classification is one of the most widely used climate classification systems. It was first published by German-Russian climatologist Wladimir Köppen (1846–1940) in 1884, with several later modifications by Köppen, notably i ...
. The Thornthwaite system, in use since 1948, incorporates
evapotranspiration Evapotranspiration (ET) is the sum of water evaporation and transpiration from a surface area to the atmosphere. Evaporation accounts for the movement of water to the air from sources such as the soil, canopy interception, and water bodies. Transpi ...
along with temperature and precipitation information and is used in studying biological diversity and how
climate change Climate change includes both global warming driven by human emissions of greenhouse gases and the resulting large-scale shifts in weather patterns. Though there have been previous periods of climatic change, since the mid-20th century hu ...
affects it. The Bergeron and
Spatial Synoptic Classification systemBased upon the Bergeron air mass classification scheme is the Spatial Synoptic Classification system, or SSC. There are six categories within the SSC scheme: Dry Polar (similar to continental polar), Dry Moderate (similar to maritime superior), Dr ...
s focus on the origin of air masses that define the climate of a region.
Paleoclimatology Paleoclimatology (in British spelling, palaeoclimatology) is the study of climates for which direct measurements were not taken. As instrumental records only span a tiny part of Earth's history, the reconstruction of ancient climate is important t ...
is the study of ancient climates. Since very few direct observations of climate are available before the 19th century, paleoclimates are inferred from proxy variables that include non-biotic evidence such as sediments found in
lake beds A lake is an area filled with water, localized in a basin, surrounded by land, apart from any river or other outlet that serves to feed or drain the lake. Lakes lie on land and are not part of the ocean, although like the much larger oceans, ...
and
ice core An ice core is a core sample that is typically removed from an ice sheet or a high mountain glacier. Since the ice forms from the incremental buildup of annual layers of snow, lower layers are older than upper, and an ice core contains ice form ...
s, and biotic evidence such as
tree rings Dendrochronology (or tree-ring dating) is the scientific method of dating tree rings (also called growth rings) to the exact year they were formed. As well as dating them this can give data for dendroclimatology, the study of climate and atmosph ...
and coral.
Climate model Numerical climate models use quantitative methods to simulate the interactions of the important drivers of climate, including atmosphere, oceans, land surface and ice. They are used for a variety of purposes from study of the dynamics of the cli ...
s are mathematical models of past, present and future climates. Climate change may occur over long and short timescales from a variety of factors; recent warming is discussed in
global warming Climate change includes both global warming driven by human emissions of greenhouse gases and the resulting large-scale shifts in weather patterns. Though there have been previous periods of climatic change, since the mid-20th century hu ...

global warming
. Global warming results in redistributions. For example, "a 3°C change in mean annual temperature corresponds to a shift in isotherms of approximately 300–400 km in latitude (in the temperate zone) or 500 m in elevation. Therefore, species are expected to move upwards in elevation or towards the poles in latitude in response to shifting climate zones".


Definition

Climate (from
Ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Dark Ages (), the Archaic period ...
''klima'', meaning ''inclination'') is commonly defined as the weather averaged over a long period. The standard averaging period is 30 years, but other periods may be used depending on the purpose. Climate also includes statistics other than the average, such as the magnitudes of day-to-day or year-to-year variations. The
Intergovernmental Panel on Climate Change The Intergovernmental Panel on Climate Change (IPCC) is an intergovernmental body of the United Nations that is dedicated to providing the world with objective, scientific information relevant to understanding the scientific basis of the risk of ...
(IPCC)
2001 2001 was designated as International Year of Volunteers. Events January * January 1 – Kolkata (in West Bengal, India) officially restores its name from Calcutta. * January 9 – iTunes is launched. * January 10 – The U.S. ...
glossary definition is as follows: The
World Meteorological Organization The World Meteorological Organization (WMO) is a specialized agency of the United Nations responsible for promoting international cooperation on atmospheric science, climatology, hydrology and geophysics. The WMO originated from the Internat ...
(WMO) describes "
climate normalClimatological normal or climate normal (CN) is a 30-year average of a weather variable for a given time of year. The WMO originated from the
International Meteorological Organization The International Meteorological Organization (IMO; 1873–1951) was the first organization formed with the purpose of exchanging weather information among the countries of the world. It came into existence from the realization that weather systems ...
which set up a technical commission for climatology in 1929. At its 1934
Wiesbaden Wiesbaden () is a city in central western Germany and the capital of the state of Hesse. , it had 290,955 inhabitants, plus approximately 19,000 United States citizens (mostly associated with the United States Army). The Wiesbaden urban area i ...
meeting the technical commission designated the thirty-year period from 1901 to 1930 as the reference time frame for climatological standard normals. In 1982 the WMO agreed to update climate normals, and these were subsequently completed on the basis of climate data from 1 January 1961 to 31 December 1990. The difference between climate and weather is usefully summarized by the popular phrase "Climate is what you expect, weather is what you get." Over
historical History (from Greek , ''historia'', meaning "inquiry; knowledge acquired by investigation") is the study of the past. Events occurring before the invention of writing systems are considered prehistory. "History" is an umbrella term that relates t ...

historical
time spans, there are a number of nearly constant variables that determine climate, including
latitude In geography, latitude is a geographic coordinate that specifies the north–south position of a point on the Earth's surface. Latitude is an angle (defined below) which ranges from 0° at the Equator to 90° (North or South) at the poles. Lines ...
, altitude, proportion of land to water, and proximity to oceans and mountains. All of these variables change only over periods of millions of years due to processes such as
plate tectonics upright=1.35, Diagram of the internal layering of Earth showing the lithosphere above the asthenosphere (not to scale) Plate tectonics (from the la, label=Late Latin, tectonicus, from the grc, τεκτονικός, lit=pertaining to building) is a ...
. Other climate determinants are more dynamic: the
thermohaline circulation 350px, A summary of the path of the thermohaline circulation. Blue paths represent deep-water currents, while red paths represent surface currents. Thermohaline circulation (THC) is a part of the large-scale ocean circulation that is driven by glo ...

thermohaline circulation
of the ocean leads to a 5 °C (9 °F) warming of the northern
Atlantic Ocean#REDIRECT Atlantic Ocean#REDIRECT Atlantic Ocean {{Redirect category shell, 1= {{R from other capitalisation ...
{{Redirect category shell, 1= {{R from other capitalisation ...

Atlantic Ocean
compared to other ocean basins. Other
ocean current An ocean current is a continuous, directed movement of sea water generated by a number of forces acting upon the water, including wind, the Coriolis effect, breaking waves, cabbeling, and temperature and salinity differences. Depth contours, s ...
s redistribute heat between land and water on a more regional scale. The density and type of vegetation coverage affects solar heat absorption, water retention, and rainfall on a regional level. Alterations in the quantity of atmospheric
greenhouse gas A greenhouse gas (sometimes abbreviated GHG) is a gas that absorbs and emits radiant energy within the thermal infrared range, causing the greenhouse effect. The primary greenhouse gases in Earth's atmosphere are water vapor (), carbon dioxid ...
es determines the amount of solar energy retained by the planet, leading to
global warming Climate change includes both global warming driven by human emissions of greenhouse gases and the resulting large-scale shifts in weather patterns. Though there have been previous periods of climatic change, since the mid-20th century hu ...

global warming
or
global cooling thumb Global cooling was a conjecture, especially during the 1970s, of imminent cooling of the Earth culminating in a period of extensive glaciation, due to the cooling effects of aerosols and orbital forcing. Some press reports in the 1970s spec ...
. The variables which determine climate are numerous and the interactions complex, but there is general agreement that the broad outlines are understood, at least insofar as the determinants of historical climate change are concerned.


Climate classification

There are several ways to classify climates into similar regimes. Originally,
clime frame, Diagram showing climatic zone corresponding with those suggested by Aristotle. The climes (singular ''clime''; also ''clima'', plural ''climata'', from Greek κλίμα ''klima'', plural κλίματα ''klimata'', meaning "inclination" or ...
s were defined in
Ancient Greece Ancient Greece ( el, Ἑλλάς, Hellás) was a civilization belonging to a period of Greek history from the Greek Dark Ages of the 12th–9th centuries BC to the end of antiquity ( AD 600). This era was immediately followed by the Early Middle ...
to describe the weather depending upon a location's latitude. Modern climate classification methods can be broadly divided into ''genetic'' methods, which focus on the causes of climate, and ''empiric'' methods, which focus on the effects of climate. Examples of genetic classification include methods based on the
relative frequency In statistics the frequency (or absolute frequency) of an event i is the number n_i of times the observation occurred/recorded in an experiment or study. These frequencies are often graphically represented in histograms. Types The cumulative fre ...
of different
air mass upright=1.25, Different air masses which affect North America as well as other continents, tend to be separated by frontal boundaries In meteorology, an air mass is a volume of air defined by its temperature and water vapor content. Air masses co ...
types or locations within
synoptic Synoptic may refer to: *Synoptic scale meteorology, a meteorological analysis over an area about 1000 kilometres or more wide *Synoptic Gospels, in the New Testament of the Bible, the gospels of Matthew, Mark, and Luke *Synoptic philosophy, wisdom ...
weather disturbances. Examples of empiric classifications include
climate zone350px, Leslie Holdridge's Life Zone Classification system is essentially a climate classification scheme. Climate classification is a way of categorizing the world's climates. A climate classification may correlate closely with a biome category, as c ...
s defined by
plant hardiness Hardiness of plants describes their ability to survive adverse growing conditions. It is usually limited to discussions of climatic adversity. Thus a plant's ability to tolerate cold, heat, drought, flooding, or wind are typically considered measure ...
, evapotranspiration, or more generally the
Köppen climate classification The Köppen climate classification is one of the most widely used climate classification systems. It was first published by German-Russian climatologist Wladimir Köppen (1846–1940) in 1884, with several later modifications by Köppen, notably i ...
which was originally designed to identify the climates associated with certain
biome A biome is a collection of plants and animals that have common characteristics for the environment they exist in. They can be found over a range of continents. Biomes are distinct biological communities that have formed in response to a shared p ...
s. A common shortcoming of these
classification scheme In information science and ontology, a classification scheme is the product of arranging things into kinds of things (classes) or into ''groups'' of classes; this bears similarity to categorization, but with perhaps a more theoretical bent, as clas ...
s is that they produce distinct boundaries between the zones they define, rather than the gradual transition of climate properties more common in nature.


Bergeron and Spatial Synoptic

The simplest classification is that involving
air mass upright=1.25, Different air masses which affect North America as well as other continents, tend to be separated by frontal boundaries In meteorology, an air mass is a volume of air defined by its temperature and water vapor content. Air masses co ...
es. The Bergeron classification is the most widely accepted form of air mass classification. Air mass classification involves three letters. The first letter describes its
moisture {{unreferenced, date=March 2008 150px, Dew on a spider web Moisture is the presence of a liquid, especially water, often in trace amounts. Small amounts of water may be found, for example, in the air (humidity), in foods, and in some commercial prod ...
properties, with c used for continental air masses (dry) and m for maritime air masses (moist). The second letter describes the thermal characteristic of its source region: T for
tropical The tropics are the region of Earth surrounding the Equator. They are delimited in latitude by the Tropic of Cancer in the Northern Hemisphere at N and the Tropic of Capricorn in the Southern Hemisphere at S; these latitudes correspond to the ...
, P for
polar Polar may refer to: Geography Polar may refer to: * Geographical pole, either of two fixed points on the surface of a rotating body or planet, at 90 degrees from the equator, based on the axis around which a body rotates *Polar climate, the clima ...
, A for
Arctic Artificially coloured topographical map of the Arctic region The Arctic ( or ) is a polar region located at the northernmost part of Earth. The Arctic consists of the Arctic Ocean, adjacent seas, and parts of Alaska (United States), Canada, ...

Arctic
or Antarctic, M for
monsoon A monsoon () is traditionally a seasonal reversing wind accompanied by corresponding changes in precipitation, but is now used to describe seasonal changes in atmospheric circulation and precipitation associated with the asymmetric heating of ...
, E for equatorial, and S for superior air (dry air formed by significant downward motion in the atmosphere). The third letter is used to designate the stability of the
atmosphere An atmosphere (from the greek words ἀτμός ''(atmos)'', meaning 'vapour', and σφαῖρα ''(sphaira)'', meaning 'ball' or 'sphere') is a layer or a set of layers of gases surrounding a planet or other material body, that is held in pla ...
. If the air mass is colder than the ground below it, it is labeled k. If the air mass is warmer than the ground below it, it is labeled w. While air mass identification was originally used in
weather forecasting Weather forecasting is the application of science and technology to predict the conditions of the atmosphere for a given location and time. People have attempted to predict the weather informally for millennia and formally since the 19th century ...
during the 1950s, climatologists began to establish synoptic climatologies based on this idea in 1973. Based upon the Bergeron classification scheme is the
Spatial Synoptic Classification systemBased upon the Bergeron air mass classification scheme is the Spatial Synoptic Classification system, or SSC. There are six categories within the SSC scheme: Dry Polar (similar to continental polar), Dry Moderate (similar to maritime superior), Dr ...
(SSC). There are six categories within the SSC scheme: Dry Polar (similar to continental polar), Dry Moderate (similar to maritime superior), Dry Tropical (similar to continental tropical), Moist Polar (similar to maritime polar), Moist Moderate (a hybrid between maritime polar and maritime tropical), and Moist Tropical (similar to maritime tropical, maritime monsoon, or maritime equatorial).


Köppen

The Köppen classification depends on average monthly values of temperature and precipitation. The most commonly used form of the Köppen classification has five primary types labeled A through E. These primary types are A) tropical, B) dry, C) mild mid-latitude, D) cold mid-latitude, and E) polar. The five primary classifications can be further divided into secondary classifications such as
rainforest Rainforests are forests characterized by high and continuous rainfall, with annual rainfall in the case of tropical rainforests between and definitions varying by region for temperate rainforests. The monsoon trough, alternatively known as the ...
,
monsoon A monsoon () is traditionally a seasonal reversing wind accompanied by corresponding changes in precipitation, but is now used to describe seasonal changes in atmospheric circulation and precipitation associated with the asymmetric heating of ...
,
tropical savanna Tropical and subtropical grasslands, savannas, and shrublands is a terrestrial biome defined by the World Wide Fund for Nature. The biome is dominated by grass and/or shrubs located in semi-arid to semi-humid climate regions of subtropical and tr ...
,
humid subtropical A humid subtropical climate is a zone of climate characterized by hot and humid summers, and cold to mild winters. These climates normally lie on the southeast side of all continents, generally between latitudes 25° and 40° (sometimes 45°) an ...
,
humid continental A humid continental climate is a climatic region defined by Russo-German climatologist Wladimir Köppen in 1900, typified by four distinct seasons and large seasonal temperature differences, with warm to hot (and often humid) summers and cold (som ...
,
oceanic climate Oceanic may refer to: *Of or relating to the ocean *Of or relating to Oceania **Oceanic climate **Oceanic languages **Oceanic person or people, also called "Pacific Islander(s)" Places *Oceanic, British Columbia, a settlement on Smith Island, Br ...
,
Mediterranean climate The coastal Mediterranean region of Costa Brava, Catalonia, Spain">Catalonia.html" style="text-decoration: none;"class="mw-redirect" title="Costa Brava, Catalonia">Costa Brava, Catalonia, Spain A Mediterranean climate or dry summer c ...
,
desert upright=1.5, alt=see caption, Sand dunes in the Rub' al Khali ("Empty quarter") in the United Arab Emirates A desert is a barren area of landscape where little precipitation occurs and, consequently, living conditions are hostile for ...
,
steppe File:Steppe of western Kazakhstan in the early spring.jpg, Steppe in Kazakhstan In physical geography, a steppe is an ecoregion characterized by grassland plains without trees apart from those near rivers and lakes. Steppe b ...
,
subarctic climate#REDIRECT Subarctic climate#REDIRECT Subarctic climate {{R from other capitalisation ...
{{R from other capitalisation ...
,
tundra In physical geography, tundra () is a type of biome where the tree growth is hindered by low temperatures and short growing seasons. The term ''tundra'' comes through Russian (') from the Kildin Sámi word (') meaning "uplands", "treeless mount ...
, and
polar ice cap A polar ice cap or polar cap is a high-latitude region of a planet, dwarf planet, or natural satellite that is covered in ice. There are no requirements with respect to size or composition for a body of ice to be termed a polar ice cap, nor an ...
. Rainforests are characterized by high
rainfall Rain is liquid water in the form of droplets that have condensed from atmospheric water vapor and then become heavy enough to fall under gravity. Rain is a major component of the water cycle and is responsible for depositing most of the fres ...
, with definitions setting minimum normal annual rainfall between and . Mean monthly temperatures exceed during all months of the year. A monsoon is a seasonal prevailing wind which lasts for several months, ushering in a region's rainy season. Regions within
North America North America is a continent entirely within the Northern Hemisphere and almost all within the Western Hemisphere. It can also be described as the northern subcontinent of the Americas. It is bordered to the north by the Arctic Ocean, to ...

North America
,
South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. It can also be described as a southern subcontinent of the Americas. The ref ...
,
Sub-Saharan Africa Sub-Saharan Africa is, geographically and ethnoculturally, the area of the continent of Africa that lies south of the Sahara. According to the United Nations, it consists of all African countries and territories that are fully or partially so ...
,
Australia Australia, officially the Commonwealth of Australia, is a sovereign country comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands. It is the largest country in Oceania and the world's sixt ...

Australia
and
East Asia East Asia is the eastern region of Asia, which is defined in both geographical and ethno-cultural terms. The modern states of East Asia include China, Japan, Mongolia, North Korea, South Korea, and Taiwan. The East Asian states of China, North ...
are monsoon regimes. A tropical savanna is a
grassland Grasslands are areas where the vegetation is dominated by grasses (Poaceae). However, sedge (Cyperaceae) and rush (Juncaceae) can also be found along with variable proportions of legumes, like clover, and other herbs. Grasslands occur naturally ...
biome A biome is a collection of plants and animals that have common characteristics for the environment they exist in. They can be found over a range of continents. Biomes are distinct biological communities that have formed in response to a shared p ...
located in
semi-arid A semi-arid climate, semi-desert climate, or steppe climate is the climate of a region that receives precipitation below potential evapotranspiration, but not as low as a desert climate. There are different kinds of semi-arid climates, depending on ...
to semi-
humid Humidity is the concentration of water vapor present in the air. Water vapor, the gaseous state of water, is generally invisible to the human eye. Humidity indicates the likelihood for precipitation, dew, or fog to be present. Humidity depends o ...

humid
climate regions of
subtropical The subtropical zones or subtropics are geographic and climate zones located to the north and south of the tropical zone. Geographically part of the north and south temperate zones, they cover the latitudes between 23°26′11.6″ and approxim ...

subtropical
and
tropical The tropics are the region of Earth surrounding the Equator. They are delimited in latitude by the Tropic of Cancer in the Northern Hemisphere at N and the Tropic of Capricorn in the Southern Hemisphere at S; these latitudes correspond to the ...
latitude In geography, latitude is a geographic coordinate that specifies the north–south position of a point on the Earth's surface. Latitude is an angle (defined below) which ranges from 0° at the Equator to 90° (North or South) at the poles. Lines ...
s, with average temperatures remaining at or above all year round, and rainfall between and a year. They are widespread on
Africa Africa is the world's second-largest and second-most populous continent, after Asia in both cases. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 6% of Earth's total surface area and 20% of it ...

Africa
, and are found in
India India (Hindi: ), officially the Republic of India (Hindi: ), is a country in South Asia. It is the second-most populous country, the seventh-largest country by land area, and the most populous democracy in the world. Bounded by the Indian Oce ...

India
, the northern parts of
South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. It can also be described as a southern subcontinent of the Americas. The ref ...
,
Malaysia Malaysia ( ; ) is a country in Southeast Asia. The federal constitutional monarchy consists of thirteen states and three federal territories, separated by the South China Sea into two regions, Peninsular Malaysia and Borneo's East Malaysia. Pe ...

Malaysia
, and
Australia Australia, officially the Commonwealth of Australia, is a sovereign country comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands. It is the largest country in Oceania and the world's sixt ...

Australia
.Susan Woodward
Tropical Savannas.
Retrieved on 2008-03-16.
The humid subtropical climate zone where winter rainfall (and sometimes
snowfall Snow comprises individual ice crystals that grow while suspended in the atmosphere—usually within clouds—and then fall, accumulating on the ground where they undergo further changes. It consists of frozen crystalline water throughout i ...
) is associated with large
storm A storm is any disturbed state of an environment or in an astronomical body's atmosphere especially affecting its surface, and strongly implying severe weather. It may be marked by significant disruptions to normal conditions such as strong wind ...
s that the
westerlies The westerlies, anti-trades, or prevailing westerlies, are prevailing winds from the west toward the east in the middle latitudes between 30 and 60 degrees latitude. They originate from the high-pressure areas in the horse latitudes and trend tow ...
steer from west to east. Most summer rainfall occurs during
thunderstorm A thunderstorm, (also known as an electrical storm or a lightning storm) is a storm characterized by the presence of lightning and its acoustic effect on the Earth's atmosphere, known as thunder. (There are relativitly weak thunderstorms,some ...
s and from occasional
tropical cyclone A tropical cyclone is a rapidly rotating storm system characterized by a low-pressure center, a closed low-level atmospheric circulation, strong winds, and a spiral arrangement of thunderstorms that produce heavy rain and/or squalls. Dependin ...
s. Humid subtropical climates lie on the east side of continents, roughly between
latitude In geography, latitude is a geographic coordinate that specifies the north–south position of a point on the Earth's surface. Latitude is an angle (defined below) which ranges from 0° at the Equator to 90° (North or South) at the poles. Lines ...
s 20° and 40° degrees away from the
equator The Earth's equator is an imaginary planetary line that is about long in circumference. The equator divides the planet into the Northern Hemisphere and Southern Hemisphere and is located at 0 degrees latitude, the halfway line between the Nor ...
. A humid continental climate is marked by variable weather patterns and a large seasonal temperature variance. Places with more than three months of average daily temperatures above and a coldest month temperature below and which do not meet the criteria for an
arid A region is arid when it is characterized by a severe lack of available water, to the extent of hindering or preventing the growth and development of plant and animal life. Environments subject to arid climates tend to lack vegetation and are ca ...
or
semi-arid climate A semi-arid climate, semi-desert climate, or steppe climate is the climate of a region that receives precipitation below potential evapotranspiration, but not as low as a desert climate. There are different kinds of semi-arid climates, depending on ...
, are classified as continental. An oceanic climate is typically found along the west coasts at the middle latitudes of all the world's continents, and in southeastern
Australia Australia, officially the Commonwealth of Australia, is a sovereign country comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands. It is the largest country in Oceania and the world's sixt ...

Australia
, and is accompanied by plentiful precipitation year-round. The Mediterranean climate regime resembles the climate of the lands in the
Mediterranean Basin In biogeography, the Mediterranean Basin (also known as the Mediterranean region or sometimes Mediterranea) is the region of lands around the Mediterranean Sea that have a Mediterranean climate, with mild, rainy winters and hot, dry summers, wh ...
, parts of western
North America North America is a continent entirely within the Northern Hemisphere and almost all within the Western Hemisphere. It can also be described as the northern subcontinent of the Americas. It is bordered to the north by the Arctic Ocean, to ...

North America
, parts of
Western Western may refer to: Places *Western, Nebraska, a village in the US *Western, New York, a town in the US *Western Creek, Tasmania, a locality in Australia *Western Junction, Tasmania, a locality in Australia *Western world, countries that ide ...
and
South Australia South Australia (abbreviated as SA) is a state in the southern central part of Australia. It covers some of the most arid parts of the country. With a total land area of , it is the fourth-largest of Australia's states and territories by area, a ...
, in southwestern
South Africa South Africa, officially the Republic of South Africa (RSA), is the southernmost country in Africa. With over 59 million people, it is the world's 23rd-most populous nation and covers an area of . South Africa has three capital cities: e ...
and in parts of central
Chile Chile (, ; ), officially the Republic of Chile (), is a country in western South America. It occupies a long, narrow strip of land between the Andes to the east and the Pacific Ocean to the west. Chile covers an area of and has a population ...
. The climate is characterized by hot, dry summers and cool, wet winters. A steppe is a dry
grassland Grasslands are areas where the vegetation is dominated by grasses (Poaceae). However, sedge (Cyperaceae) and rush (Juncaceae) can also be found along with variable proportions of legumes, like clover, and other herbs. Grasslands occur naturally ...
with an annual temperature range in the summer of up to and during the winter down to . A subarctic climate has little precipitation,Michael Ritter
Subarctic Climate.
Retrieved on 2008-04-16.
and monthly temperatures which are above for one to three months of the year, with
permafrost Permafrost is ground that continuously remains below 0°C (32°F) for two or more years, located on land or under the ocean. Permafrost does not have to be the first layer that is on the ground. It can be from an inch to several miles deep under ...
in large parts of the area due to the cold winters. Winters within subarctic climates usually include up to six months of temperatures averaging below . Tundra occurs in the far
Northern Hemisphere The Northern Hemisphere is the half of the Earth that is north of the Equator. For other planets in the Solar System, north is defined as being in the same celestial hemisphere relative to the invariable plane of the solar system as Earth's N ...
, north of the
taiga Taiga (; rus, тайга́, p=tɐjˈɡa; relates to Mongolic and Turkic languages), generally referred to in North America as boreal forest or snow forest, is a biome characterized by coniferous forests consisting mostly of pines, spruces, and la ...
belt, including vast areas of northern
Russia Russia (russian: link=no, Россия, , ), or the Russian Federation, is a country spanning Eastern Europe and Northern Asia. It is the largest country in the world, covering and encompassing more than one-eighth of the Earth's inhabited l ...
and
Canada Canada is a country in the northern part of North America. Its ten provinces and three territories extend from the Atlantic to the Pacific and northward into the Arctic Ocean, covering , making it the world's second-largest country by total ...

Canada
. A polar ice cap, or polar ice sheet, is a high-
latitude In geography, latitude is a geographic coordinate that specifies the north–south position of a point on the Earth's surface. Latitude is an angle (defined below) which ranges from 0° at the Equator to 90° (North or South) at the poles. Lines ...
region of a
planet A planet is an astronomical body orbiting a star or stellar remnant that is massive enough to be rounded by its own gravity, is not massive enough to cause thermonuclear fusion, and – according to the International Astronomical Union but not ...
or
moon The Moon is Earth's only proper natural satellite. At one-quarter the diameter of Earth (comparable to the width of Australia), it is the largest natural satellite in the Solar System relative to the size of its planet, and the fifth largest ...
that is covered in ice. Ice caps form because high-
latitude In geography, latitude is a geographic coordinate that specifies the north–south position of a point on the Earth's surface. Latitude is an angle (defined below) which ranges from 0° at the Equator to 90° (North or South) at the poles. Lines ...
regions receive less energy as solar radiation from the sun than
equator The Earth's equator is an imaginary planetary line that is about long in circumference. The equator divides the planet into the Northern Hemisphere and Southern Hemisphere and is located at 0 degrees latitude, the halfway line between the Nor ...
ial regions, resulting in lower Surface air temperature, surface temperatures. A desert is a landscape form or region that receives very little precipitation (meteorology), precipitation. Deserts usually have a large Diurnal temperature variation, diurnal and seasonal temperature range, with high or low, depending on location daytime temperatures (in summer up to ), and low nighttime temperatures (in winter down to ) due to extremely low
humidity Humidity is the concentration of water vapor present in the air. Water vapor, the gaseous state of water, is generally invisible to the human eye. Humidity indicates the likelihood for precipitation, dew, or fog to be present. Humidity depends o ...

humidity
. Many deserts are formed by rain shadows, as mountains block the path of moisture and precipitation to the desert.


Thornthwaite

Devised by the American climatologist and geographer C. W. Thornthwaite, this climate classification method monitors the soil water budget using evapotranspiration.Glossary of Meteorology
Thornthwaite Moisture Index.
Retrieved on 2008-05-21.
It monitors the portion of total precipitation used to nourish vegetation over a certain area. It uses indices such as a humidity index and an aridity index to determine an area's moisture regime based upon its average temperature, average rainfall, and average vegetation type. The lower the value of the index in any given area, the drier the area is. The moisture classification includes climatic classes with descriptors such as hyperhumid, humid, subhumid, subarid, semi-arid (values of −20 to −40), and arid (values below −40). Humid regions experience more precipitation than evaporation each year, while arid regions experience greater evaporation than precipitation on an annual basis. A total of 33 percent of the Earth's landmass is considered either arid or semi-arid, including southwest North America, southwest South America, most of northern and a small part of southern Africa, southwest and portions of eastern Asia, as well as much of Australia. Studies suggest that precipitation effectiveness (PE) within the Thornthwaite moisture index is overestimated in the summer and underestimated in the winter. This index can be effectively used to determine the number of herbivore and mammal species numbers within a given area. The index is also used in studies of climate change.Gregory J. McCabe and David M. Wolock
Trends and temperature sensitivity of moisture conditions in the conterminous United States.
Retrieved on 2008-05-21.
Thermal classifications within the Thornthwaite scheme include microthermal, mesothermal, and megathermal regimes. A microthermal climate is one of low annual mean temperatures, generally between and which experiences short summers and has a potential evaporation between and . A mesothermal climate lacks persistent heat or persistent cold, with potential evaporation between and . A megathermal climate is one with persistent high temperatures and abundant rainfall, with potential annual evaporation in excess of .


Record


Paleoclimatology

Paleoclimatology is the study of past climate over a great period of the Earth's history. It uses evidence from ice sheets, tree rings, sediments, coral, and rocks to determine the past state of the climate. It demonstrates periods of stability and periods of change and can indicate whether changes follow patterns such as regular cycles.


Modern

Details of the modern climate record are known through the taking of measurements from such weather instruments as thermometers, barometers, and anemometers during the past few centuries. The instruments used to study weather over the modern time scale, their known error, their immediate environment, and their exposure have changed over the years, which must be considered when studying the climate of centuries past.


Climate variability

Climate variability is the term to describe variations in the mean state and other characteristics of climate (such as chances or possibility of extreme weather, etc.) "on all spatial and temporal scales beyond that of individual weather events." Some of the variability does not appear to be caused systematically and occurs at random times. Such variability is called ''random variability'' or ''Noise (signal processing), noise''. On the other hand, periodic variability occurs relatively regularly and in distinct modes of variability or climate patterns. There are close correlations between Earth's climate oscillations and astronomical factors (barycenter changes, solar variation, cosmic ray flux, cloud albedo cloud feedback, feedback, Milankovic cycles), and modes of thermodynamics, heat distribution between the ocean-atmosphere climate system. In some cases, current, historical and paleoclimate, paleoclimatological natural oscillations may be masked by significant volcanic eruptions, impact events, irregularities in climate proxy data, positive feedback processes or Human impact on the environment, anthropogenic Greenhouse gas#Greenhouse gas emissions, emissions of substances such as
greenhouse gas A greenhouse gas (sometimes abbreviated GHG) is a gas that absorbs and emits radiant energy within the thermal infrared range, causing the greenhouse effect. The primary greenhouse gases in Earth's atmosphere are water vapor (), carbon dioxid ...
es. Over the years, the definitions of ''climate variability'' and the related term ''
climate change Climate change includes both global warming driven by human emissions of greenhouse gases and the resulting large-scale shifts in weather patterns. Though there have been previous periods of climatic change, since the mid-20th century hu ...
'' have shifted. While the term ''climate change'' now implies change that is both long-term and of human causation, in the 1960s the word climate change was used for what we now describe as climate variability, that is, climatic inconsistencies and anomalies.


Climate change

Climate change is the variation in global or regional climates over time. It reflects changes in the variability or average state of the atmosphere over time scales ranging from decades to millions of years. These changes can be caused by processes internal to the Earth, external forces (e.g. variations in sunlight intensity) or, more recently, human activities. In recent usage, especially in the context of environmental policy, the term "climate change" often refers only to changes in modern climate, including the rise in average surface
temperature Temperature is a physical quantity that expresses hot and cold. It is the manifestation of thermal energy, present in all matter, which is the source of the occurrence of heat, a flow of energy, when a body is in contact with another that is ...
known as
global warming Climate change includes both global warming driven by human emissions of greenhouse gases and the resulting large-scale shifts in weather patterns. Though there have been previous periods of climatic change, since the mid-20th century hu ...

global warming
. In some cases, the term is also used with a presumption of human causation, as in the United Nations UNFCCC, Framework Convention on Climate Change (UNFCCC). The UNFCCC uses "climate variability" for non-human caused variations. Earth has undergone periodic climate shifts in the past, including four major ice ages. These consisting of glacial periods where conditions are colder than normal, separated by interglacial periods. The accumulation of snow and ice during a glacial period increases the surface albedo, reflecting more of the Sun's energy into space and maintaining a lower atmospheric temperature. Increases in
greenhouse gas A greenhouse gas (sometimes abbreviated GHG) is a gas that absorbs and emits radiant energy within the thermal infrared range, causing the greenhouse effect. The primary greenhouse gases in Earth's atmosphere are water vapor (), carbon dioxid ...
es, such as by Volcanic impacts on the oceans, volcanic activity, can increase the global temperature and produce an interglacial period. Suggested causes of ice age periods include the positions of the continents, variations in the Earth's orbit, changes in the solar output, and volcanism.


Climate models

Climate model Numerical climate models use quantitative methods to simulate the interactions of the important drivers of climate, including atmosphere, oceans, land surface and ice. They are used for a variety of purposes from study of the dynamics of the cli ...
s use quantitative methods to simulate the interactions of the Earth's atmosphere, atmosphere, oceans, land surface and ice. They are used for a variety of purposes; from the study of the dynamics of the weather and climate system, to projections of future climate. All climate models balance, or very nearly balance, incoming energy as short wave (including visible) electromagnetic radiation to the earth with outgoing energy as long wave (infrared) electromagnetic radiation from the earth. Any imbalance results in a change in the average temperature of the earth. The most talked-about applications of these models in recent years have been their use to infer the consequences of increasing greenhouse gases in the atmosphere, primarily carbon dioxide (see
greenhouse gas A greenhouse gas (sometimes abbreviated GHG) is a gas that absorbs and emits radiant energy within the thermal infrared range, causing the greenhouse effect. The primary greenhouse gases in Earth's atmosphere are water vapor (), carbon dioxid ...
). These models predict an upward trend in the surface temperature record, global mean surface temperature, with the most rapid increase in temperature being projected for the higher latitudes of the Northern Hemisphere. Models can range from relatively simple to quite complex: * Simple radiant heat transfer model that treats the earth as a single point and averages outgoing energy * this can be expanded vertically (radiative-convective models), or horizontally * finally, (coupled) atmosphere–ocean–sea ice global climate models discretise and solve the full equations for mass and energy transfer and radiant exchange.Climateprediction.net
Modelling the climate.
Retrieved on 2008-05-02.


See also

* Climate inertia * Climate Prediction Center * Climatic map * Climograph * Ecosystem * Effect of Sun angle on climate * Greenhouse effect * List of climate scientists * List of weather records * Microclimate * National Climatic Data Center * Outline of meteorology * Solar cycle * Tectonic–climatic interaction * Tropical marine climate * Weather and climate


References


Further reading


The Study of Climate on Alien Worlds; Characterizing atmospheres beyond our Solar System is now within our reach
Kevin Heng July–August 2012 American Scientist
Reumert, Johannes: "Vahls climatic divisions. An explanation"
(''Danish Journal of Geography, Geografisk Tidsskrift'', Band 48; 1946)


External links


NOAA Climate Services Portal

NOAA State of the Climate

NASA's Climate change and global warming portal



Climate Prediction Project

ESPERE Climate Encyclopaedia


– Arctic
A current view of the Bering Sea Ecosystem and Climate



MIL-HDBK-310, Global Climate Data
U.S. Department of Defense – Aid to derive natural environmental design criteria
IPCC Data Distribution Centre
– Climate data and guidance on use.
HistoricalClimatology.com
– Past, present and future climates – 2013.
Globalclimatemonitor
– Contains climatic information from 1901.
ClimateCharts
– Webapplication to generate climate charts for recent and historical data.
International Disaster Database

Paris Climate Conference
{{Authority control Climate, Meteorological concepts Climatology, *