Variations in CO₂, temperature and dust from the Vostok ice core over the last 450,000 years

Climate change is any long-term significant change in the “average weather” that a given region experiences. Average weather may include average temperature, precipitation and wind patterns. It involves changes in the variability or average state of the atmosphere over durations ranging from decades to millions of years. A tone may be sustained for varying lengths of time. duration is a property of tone that becomes one of the bases rhythem or an amount of Time or a particular time These changes can be caused by dynamic process on Earth, external forces including variations in sunlight intensity, and more recently by human activities.

In recent usage, especially in the context of environmental policy, the term "climate change" often refers to changes in modern climate (see global warming). Environmental policy is any (course of action deliberately taken (or not taken to manage human activities with a view to prevent reduce or mitigate harmful effects on nature and natural Climate encompasses the temperatures humidity rainfall atmospheric particle count and numerous other meteorogical factors in a given region over long periods of Global warming is the increase in the average measured temperature of the For information on temperature measurements over various periods, and the data sources available, see temperature record. For extreme records instead of records as a set of data see Temperature extremes The temperature record shows the fluctuations of the For attribution of climate change over the past century, see attribution of recent climate change. See also Global warming, Climate change, Climate change denial Attribution of recent climate change is the effort to scientifically ascertain

Climate change factors

Climate changes reflect variations within the Earth's atmosphere, processes in other parts of the Earth such as oceans and ice caps, and the effects of human activity. The cryosphere, derived from the Greek word kryo for " Cold " or "too cold" is the term which collectively describes the portions of The external factors that can shape climate are often called climate forcings and include such processes as variations in solar radiation, the Earth's orbit, and greenhouse gas concentrations. In Climate science radiative forcing is (loosely defined as the change in net Irradiance at the Tropopause. In Physics, an orbit is the gravitationally curved path of one object around a point or another body for example the gravitational orbit of a planet around a star Greenhouse gases are gaseous constituents of the atmosphere bothnatural and anthropogenic that absorb and emit radiation at specific wavelengths within the spectrum of thermal infrared

Variations within the Earth's climate

Weather is the day-to-day state of the atmosphere, and is a chaotic non-linear dynamical system. Chaos (derived from the Ancient Greek, Chaos) typically refers to Unpredictability, and is the antithesis of Cosmos. The dynamical system concept is a mathematical Formalization for any fixed "rule" which describes the Time dependence of a point's position On the other hand, climate — the average state of weather — is fairly stable and predictable. Climate includes the average temperature, amount of precipitation, days of sunlight, and other variables that might be measured at any given site. However, there are also changes within the Earth's environment that can affect the climate.

Glaciation

Percentage of advancing glaciers in the Alps in the last 80 years

Glaciers are recognized as being among the most sensitive indicators of climate change, advancing substantially during climate cooling (e. "Glacial" and "Glaciation" redirect here For the geological periods see Glacial period. g. , the Little Ice Age) and retreating during climate warming on moderate time scales. The Little Ice Age (LIA was a period of cooling occurring after a warmer era known as the Medieval Warm Period or Medieval Climate Optimum Glaciers grow and collapse, both contributing to natural variability and greatly amplifying externally forced changes. For the last century, however, glaciers have been unable to regenerate enough ice during the winters to make up for the ice lost during the summer months (see glacier retreat). A century (from the Latin centum, meaning one hundred is One hundred consecutive Years Centuries are numbered ordinally (e Ice is a Solid phase, usually crystalline, of a Non-metalic substance that is liquid or gas at Room temperature, such as Ammonia whitechuck glacier 2006jpg|right|thumb|320px|The same view as seen in 2006 where this branch of glacier retreated 1

The most significant climate processes of the last several million years are the glacial and interglacial cycles of the present ice age. An interglacial is a geological interval of warmer global average temperature that separates Glacial periods within an Ice age. An ice age is a period of long-term reduction in the Temperature of the Earth 's surface and atmosphere resulting in an expansion of continental Ice sheets Though shaped by orbital variations, the internal responses involving continental ice sheets and 130 m sea-level change certainly played a key role in deciding what climate response would be observed in most regions. Milankovitch cycles are the collective effect of changes in the Earth 's movements upon its climate named after Serbian civil engineer and Mathematician Other changes, including Heinrich events, Dansgaard–Oeschger events and the Younger Dryas show the potential for glacial variations to influence climate even in the absence of specific orbital changes. Heinrich events, first described by marine geologist Hartmut Heinrich occurred during the last glacial period or "ice age" Dansgaard - Oeschger events are rapid climate fluctuations occurring every ≈1470 (± 532 years throughout the Last glacial period. The Younger Dryas Stadial, named after the alpine / tundra wildflower Dryas octopetala, and also referred to as the Big Freeze, was a brief (approximately

Ocean variability

A schematic of modern thermohaline circulation

On the scale of decades, climate changes can also result from interaction of the atmosphere and oceans. The term thermohaline circulation (THC refers to the part of the large-scale ocean circulation that is thought to be driven by global density gradients created by surface heat and Many climate fluctuations — including not only the El Niño Southern oscillation (the best known) but also the Pacific decadal oscillation, the North Atlantic oscillation, and the Arctic oscillation — owe their existence at least in part to different ways that heat can be stored in the oceans and move between different reservoirs. El Niño-Southern Oscillation ( ENSO; commonly referred to as simply El Niño) is a global coupled ocean-atmosphere phenomenon The Pacific Decadal Oscillation (PDO is a pattern of Pacific Climate variability that shifts phases on at least inter-decadal time scale usually about 20 to 30 years The North Atlantic oscillation (NAO is a climatic phenomenon in the North Atlantic Ocean of fluctuations in the difference of Sea-level pressure between The Arctic oscillation ( AO) is the dominant pattern of non-seasonal Sea-level pressure (SLP variations north of 20N and it is characterized by SLP anomalies of one On longer time scales ocean processes such as thermohaline circulation play a key role in redistributing heat, and can dramatically affect climate. The term thermohaline circulation (THC refers to the part of the large-scale ocean circulation that is thought to be driven by global density gradients created by surface heat and

The memory of climate

More generally, most forms of internal variability in the climate system can be recognized as a form of hysteresis, meaning that the current state of climate reflects not only the inputs, but also the history of how it got there. A system with hysteresis can be summarised as a system that may be in any number of states independent of the inputs to the system For example, a decade of dry conditions may cause lakes to shrink, plains to dry up and deserts to expand. In turn, these conditions may lead to less rainfall in the following years. In short, climate change can be a self-perpetuating process because different aspects of the environment respond at different rates and in different ways to the fluctuations that inevitably occur.

Non-climate factors driving climate change

Effects of CO2 on climate change

Main article: Greenhouse gas

Carbon dioxide variations during the last 500 million years

Current studies indicate that radiative forcing by greenhouse gases is the primary cause of global warming. Greenhouse gases are gaseous constituents of the atmosphere bothnatural and anthropogenic that absorb and emit radiation at specific wavelengths within the spectrum of thermal infrared See also Global warming, Climate change, Climate change denial Attribution of recent climate change is the effort to scientifically ascertain In Climate science radiative forcing is (loosely defined as the change in net Irradiance at the Tropopause. Greenhouse gases are gaseous constituents of the atmosphere bothnatural and anthropogenic that absorb and emit radiation at specific wavelengths within the spectrum of thermal infrared Greenhouse gases are also important in understanding Earth's climate history. According to these studies, the greenhouse effect, which is the warming produced as greenhouse gases trap heat, plays a key role in regulating Earth's temperature. The Greenhouse effect refers to the change in the Thermal equilibrium temperature of a planet or moon by the presence of an Atmosphere containing gas that absorbs

Over the last 600 million years, carbon dioxide concentrations have varied from perhaps >5000 ppm to less than 200 ppm, due primarily to the effect of geological processes and biological innovations. Carbon dioxide ( Chemical formula:) is a Chemical compound composed of two Oxygen Atoms covalently bonded to a single "Parts-per" notation is used especially in Science and Engineering, to denote Ratios (relative proportions in measured quantities particularly It has been argued by Veizer et al. , 1999, that variations in greenhouse gas concentrations over tens of millions of years have not been well correlated to climate change, with plate tectonics perhaps playing a more dominant role. More recently Royer et al. ^[1] have used the CO₂-climate correlation to derive a value for the climate sensitivity. In Intergovernmental Panel on Climate Change (IPCC reports equilibrium climate sensitivity refers to the equilibrium change in global mean surface temperature following There are several examples of rapid changes in the concentrations of greenhouse gases in the Earth's atmosphere that do appear to correlate to strong warming, including the Paleocene–Eocene thermal maximum, the Permian–Triassic extinction event, and the end of the Varangian snowball earth event. Temperature and layers The temperature of the Earth's atmosphere varies with altitude the mathematical relationship between temperature and altitude varies among five The Paleocene /Eocene boundary, was marked by the most rapid and significant climatic disturbance of the Cenozoic Era. The Permian–Triassic (P–Tr extinction event, informally known as the Great Dying, was an Extinction event that occurred, and 70 percent of terrestrial The Snowball Earth Hypothesis as it was originally proposed]] Evidence The Snowball Earth hypothesis was originally devised to explain the apparent presence of

During the modern era, the naturally rising carbon dioxide levels are implicated as the primary cause of global warming since 1950. Carbon dioxide ( Chemical formula:) is a Chemical compound composed of two Oxygen Atoms covalently bonded to a single See also Global warming, Climate change, Climate change denial Attribution of recent climate change is the effort to scientifically ascertain Global warming is the increase in the average measured temperature of the According to the Intergovernmental Panel on Climate Change (IPCC), 2007, the atmospheric concentration of CO₂ in 2005 was 379 ppm³ compared to the pre-industrial levels of 280 ppm³. Thermodynamics and Le Chatelier's principle explain the characteristics of the dynamic equilibrium of a gas in solution such as the vast amount of CO₂ held in solution in the world's oceans moving into and returning from the atmosphere. In Physics, thermodynamics (from the Greek θερμη therme meaning " Heat " and δυναμις dynamis meaning " In Chemistry, Le Chatelier's Principle, also called the Le Chatelier-Braun principle, can be used to predict the effect of a change in conditions on a Chemical These principles can be observed as bubbles which rise in a pot of water heated on a stove, or in a glass of cold beer allowed to sit at room temperature; gases dissolved in liquids are released under certain circumstances.

Plate tectonics

On the longest time scales, plate tectonics will reposition continents, shape oceans, build and tear down mountains and generally serve to define the stage upon which climate exists. Plate tectonics (from Greek τέκτων tektōn "builder" or "mason" describes the large scale motions of Earth 's Lithosphere A continent is one of several large Landmasses on Earth. They are generally identified by Convention rather than any strict criteria with seven regions An ocean (from Greek, ''Okeanos'' (Oceanus) is a major body of saline water, and a principal component of the Hydrosphere. A mountain is a Landform that extends above the surrounding Terrain in a limited area with a peak More recently, plate motions have been implicated in the intensification of the present ice age when, approximately 3 million years ago, the North and South American plates collided to form the Isthmus of Panama and shut off direct mixing between the Atlantic and Pacific Oceans. An ice age is a period of long-term reduction in the Temperature of the Earth 's surface and atmosphere resulting in an expansion of continental Ice sheets The Isthmus of Panama, also historically known as the Isthmus of Darien, is the narrow strip of land that lies between the Caribbean Sea and the Pacific The Pacific Ocean is the largest of the Earth 's Oceanic divisions

Solar variation

Main article: Solar variation

Variations in solar activity during the last several centuries based on observations of sunspots and beryllium isotopes. Solar variations are changes in the amount of Solar radiation emitted by the Sun. A sunspot is a region on the Sun 's surface ( Photosphere) that is marked by intense magnetic activity which inhibits Convection, forming Beryllium (bəˈrɪliəm is a Chemical element with the symbol Be and Atomic number 4

The sun is the ultimate source of essentially all heat in the climate system. The Sun (Sol is the Star at the center of the Solar System. The energy output of the sun, which is converted to heat at the Earth's surface, is an integral part of shaping the Earth's climate. On the longest time scales, the sun itself is getting brighter with higher energy output; as it continues its main sequence, this slow change or evolution affects the Earth's atmosphere. The main sequence is the name for a continuous and distinctive band of stars that appear on a plot of stellar color versus brightness It is thought that, early in Earth's history, the sun was too cold to support liquid water at the Earth's surface, leading to what is known as the Faint young sun paradox. The history of Earth covers approximately 46 billion years (4567000000 years from Earth ’s formation out of the Solar nebula to the present The faint young Sun paradox or the faint young Sun problem describes the apparent contradiction between observations of liquid Water early in the Earth's history .

On more modern time scales, there are also a variety of forms of solar variation, including the 11-year solar cycle and longer-term modulations. Solar variations are changes in the amount of Solar radiation emitted by the Sun. The solar cycle, or the solar magnetic activity cycle, is the main source of periodic variation of all solar phenomena driving variations in Space weather. However, the 11-year sunspot cycle does not manifest itself clearly in the climatological data. Solar intensity variations are considered to have been influential in triggering the Little Ice Age, and for some of the warming observed from 1900 to 1950. The Little Ice Age (LIA was a period of cooling occurring after a warmer era known as the Medieval Warm Period or Medieval Climate Optimum The cyclical nature of the sun's energy output is not yet fully understood; it differs from the very slow change that is happening within the sun as it ages and evolves. .

Orbital variations

In their effect on climate, orbital variations are in some sense an extension of solar variability, because slight variations in the Earth's orbit lead to changes in the distribution and abundance of sunlight reaching the Earth's surface. In Physics, an orbit is the gravitationally curved path of one object around a point or another body for example the gravitational orbit of a planet around a star Such orbital variations, known as Milankovitch cycles, are a highly predictable consequence of basic physics due to the mutual interactions of the Earth, its moon, and the other planets. Milankovitch cycles are the collective effect of changes in the Earth 's movements upon its climate named after Serbian civil engineer and Mathematician These variations are considered the driving factors underlying the glacial and interglacial cycles of the present ice age. Subtler variations are also present, such as the repeated advance and retreat of the Sahara desert in response to orbital precession. The Sahara (الصحراء الكبرى aṣ-ṣaḥrā´ al-kubra, "The Great Desert" is the world's largest hot Desert and the world's second largest Precession refers to a change in the direction of the axis of a rotating object

Volcanism

A single eruption of the kind that occurs several times per century can affect climate, causing cooling for a period of a few years. Plate tectonics and hotspots Divergent plate boundaries At the For example, the eruption of Mount Pinatubo in 1991 affected climate substantially. Mount Pinatubo is an active Stratovolcano located on the island of Luzon Huge eruptions, known as large igneous provinces, occur only a few times every hundred million years, but can reshape climate for millions of years and cause mass extinctions. Large Igneous provinces (LIPS were originally defined by Coffin and Eldholm (1992 as areas of Earth's surface that contain very large volumes of magmatic rocks (typically An extinction event (also known as mass extinction; extinction-level event, ELE is a sharp decrease in the number of Species in a relatively short period Initially, scientists thought that the dust emitted into the atmosphere from large volcanic eruptions was responsible for the cooling by partially blocking the transmission of solar radiation to the Earth's surface. However, measurements indicate that most of the dust thrown in the atmosphere returns to the Earth's surface within six months.

Volcanoes are also part of the extended carbon cycle. The carbon cycle is the biogeochemical cycle by which carbon is exchanged among the Biosphere, Pedosphere, Geosphere, Hydrosphere, and Over very long (geological) time periods, they release carbon dioxide from the earth's interior, counteracting the uptake by sedimentary rocks and other geological carbon dioxide sinks. However, this contribution is insignificant compared to the current anthropogenic emissions. The US Geological Survey estimates that human activities generate more than 130 times the amount of carbon dioxide emitted by volcanoes. The United States Geological Survey ( USGS) is a scientific agency of the United States government. ^[2]

Attribution of recent climate change

Human influences on climate change

Anthropogenic factors are human activities that change the environment and influence climate. See also Global warming, Climate change, Climate change denial Attribution of recent climate change is the effort to scientifically ascertain In some cases the chain of causality is direct and unambiguous (e. g. , by the effects of irrigation on temperature and humidity), while in others it is less clear. Various hypotheses for human-induced climate change have been debated for many years.

The biggest factor of present concern is the increase in CO₂ levels due to emissions from fossil fuel combustion, followed by aerosols (particulate matter in the atmosphere), which exert a cooling effect, and cement manufacture. Fossil fuels or mineral fuels are fossil source Fuels that is Hydrocarbons found within the top layer of the Earth’s crust. Particulates, alternatively referred to as particulate matter (PM or fine particles, are tiny particles of solid or liquid suspended in a gas In the most general sense of the word a cement is a binder a substance which sets and hardens independently and can bind other materials together Other factors, including land use, ozone depletion, animal agriculture^[3] and deforestation, also affect climate. Ozone depletion describes two distinct but related observations a slow steady decline of about 4 percent per decade in the total amount of Ozone in Earth's

Fossil fuels

Carbon dioxide variations over the last 400,000 years, showing a rise since the industrial revolution.

Beginning with the industrial revolution in the 1850s and accelerating ever since, the human consumption of fossil fuels has elevated CO₂ levels from a concentration of ~280 ppm to more than 380 ppm today. The Industrial Revolution was a period in the late 18th and early 19th centuries when major changes in agriculture manufacturing and transportation had a profound effect on the These increases are projected to reach more than 560 ppm before the end of the 21st century. It is known that carbon dioxide levels are substantially higher now than at any time in the last 750,000 years. ^[4] Along with rising methane levels, these changes are anticipated to cause an increase of 1. Methane is a Chemical compound with the molecular formula. It is the simplest Alkane, and the principal component of Natural gas. 4–5. 6 °C between 1990 and 2100 (see global warming). The Celsius Temperature scale was previously known as the centigrade scale. Global warming is the increase in the average measured temperature of the

Aerosols

Anthropogenic aerosols, particularly sulphate aerosols from fossil fuel combustion, exert a cooling influence^[5]. This, together with natural variability, is believed to account for the relative "plateau" in the graph of 20th-century temperatures in the middle of the century.

Cement manufacture

Cement manufacturing is the third largest cause of man-made carbon dioxide emissions. In the most general sense of the word a cement is a binder a substance which sets and hardens independently and can bind other materials together Carbon dioxide is produced when calcium carbonate (CaCO₃) is heated to produce the cement ingredient calcium oxide (CaO, also called quicklime). Calcium carbonate is a Chemical compound with the Chemical formula Ca[[Carbon C]] O 3 Calcium oxide ( CaO) commonly known as burnt lime, lime or quicklime, is a widely used Chemical compound. While fossil fuel combustion and deforestation each produce significantly more carbon dioxide (CO₂), cement-making is responsible for approximately 2. 5% of total worldwide emissions from industrial sources (energy plus manufacturing sectors). ^[6]

Land use

Prior to widespread fossil fuel use, humanity's largest effect on local climate is likely to have resulted from land use. Land use' is also often used to refer to the distinct land use types in Zoning. Irrigation, deforestation, and agriculture fundamentally change the environment. Irrigation is an artificial application of water to the soil usually for assisting in growing crops Deforestation is the conversion of Forested areas to non-forest land for use such as Arable land, Pasture, urban use logged area or wasteland Agriculture refers to the production of goods through the growing of plants and fungi and the raising of domesticated Animals The study of agriculture For example, they change the amount of water going into and out of a given location. They also may change the local albedo by influencing the ground cover and altering the amount of sunlight that is absorbed. The albedo of an object is the extent to which it diffusely reflects light from the sun For example, there is evidence to suggest that the climate of Greece and other Mediterranean countries was permanently changed by widespread deforestation between 700 BC and 1 AD (the wood being used for shipbuilding, construction and fuel), with the result that the modern climate in the region is significantly hotter and drier, and the species of trees that were used for shipbuilding in the ancient world can no longer be found in the area. See also Shipbuilding (song. Shipbuilding is the construction of Ships It normally takes place in a specialized facility known as a In the fields of Architecture and Civil engineering, construction is a process that consists of the Building or assembling of Infrastructure

A controversial hypothesis by William Ruddiman called the early anthropocene hypothesis^[7] suggests that the rise of agriculture and the accompanying deforestation led to the increases in carbon dioxide and methane during the period 5000–8000 years ago. William F Ruddiman is a palaeoclimatologist and Professor Emeritus at the University of Virginia. The early anthropocene hypothesis (sometimes called Early Anthropogenic is a theory proposed by William Ruddiman. These increases, which reversed previous declines, may have been responsible for delaying the onset of the next glacial period, according to Ruddimann's overdue-glaciation hypothesis. The early anthropocene hypothesis (sometimes called Early Anthropogenic is a theory proposed by William Ruddiman.

In modern times, a 2007 Jet Propulsion Laboratory study ^[8] found that the average temperature of California has risen about 2 degrees over the past 50 years, with a much higher increase in urban areas. California ( is a US state on the West Coast of the United States, along the Pacific Ocean. The change was attributed mostly to extensive human development of the landscape.

Livestock

According to a 2006 United Nations report, Livestock's Long Shadow, livestock is responsible for 18% of the world’s greenhouse gas emissions as measured in CO₂ equivalents. Livestock's Long Shadow - Environmental Issues and Options is a United Nations report released by the Food and Agriculture Organisation of the United Nations This however includes land usage change, meaning deforestation in order to create grazing land. In the Amazon Rainforest, 70% of deforestation is to make way for grazing land, so this is the major factor in the 2006 UN FAO report, which was the first agricultural report to include land usage change into the radiative forcing of livestock. The Amazon Rainforest (Brazilian Portuguese: Floresta Amazônica or Amazônia; Spanish: Selva Amazónica or Amazonía In addition to CO₂ emissions, livestock produces 65% of human-induced nitrous oxide (which has 296 times the global warming potential of CO₂) and 37% of human-induced methane (which has 23 times the global warming potential of CO₂). Nitrous oxide, commonly known as " laughing gas," is a Chemical compound with the Chemical formula N 2 O. Global warming potential (GWP is a measure of how much a given mass of Greenhouse gas is estimated to contribute to Global warming. ^[3]

Interplay of factors

If a certain forcing (for example, solar variation) acts to change the climate, then there may be mechanisms that act to amplify or reduce the effects. These are called positive and negative feedbacks. Positive feedback, sometimes referred to as "cumulative causation" is a Feedback loop system in which the system responds to perturbation in the same direction Negative Feedback feeds part of a System 's output inverted into the system's input generally with the result that fluctuations are attenuated As far as is known, the climate system is generally stable with respect to these feedbacks: positive feedbacks do not "run away". Feedback runaway is a situation in a Feedback system where (usually positive) feedback causes an undesirable situation to become worse Part of the reason for this is the existence of a powerful negative feedback between temperature and emitted radiation: radiation increases as the fourth power of absolute temperature. In Arithmetic and Algebra, the fourth power of a number n is the result of multiplying n by itself four times Thermodynamic temperature is the absolute measure of Temperature and is one of the principal parameters of Thermodynamics.

However, a number of important positive feedbacks do exist. The glacial and interglacial cycles of the present ice age provide an important example. It is believed that orbital variations provide the timing for the growth and retreat of ice sheets. However, the ice sheets themselves reflect sunlight back into space and hence promote cooling and their own growth, known as the ice-albedo feedback. Further, falling sea levels and expanding ice decrease plant growth and indirectly lead to declines in carbon dioxide and methane. This leads to further cooling. Conversely, rising temperatures caused, for example, by anthropogenic emissions of greenhouse gases could lead to decreased snow and ice cover, revealing darker ground underneath, and consequently result in more absorption of sunlight. ^[9]

Water vapor, methane, and carbon dioxide can also act as significant positive feedbacks, their levels rising in response to a warming trend, thereby accelerating that trend. Water vapor acts strictly as a feedback (excepting small amounts in the stratosphere), unlike the other major greenhouse gases, which can also act as forcings. The stratosphere is the second major layer of Earth's atmosphere, just above the Troposphere, and below the Mesosphere.

More complex feedbacks include heat movement from the equatorial regions to the northern latitudes and involve the possibility of altered water currents with in the oceans or air currents with in the atmosphere. A significant concern is that melting glacial ice from Greenland may interfere and change the thermohaline circulation of water in the North Atlantic, affecting the Gulf Stream which brings warmer water to replace sinking colder water; which would change the distribution of heat to Europe and the east coast of the United States. Greenland (Kalaallit Nunaat meaning "Land of the Greenlanders" Grønland is a self-governing Danish Province located between the The Gulf Stream, together with its northern extension towards Europe the North Atlantic Drift, is a powerful warm and swift Atlantic Ocean current that The United States of America —commonly referred to as the

Other potential feedbacks are not well understood and may either inhibit or promote warming. For example, it is unclear whether rising temperatures promote or inhibit vegetative growth, which could in turn draw down either more or less carbon dioxide. Similarly, increasing temperatures may lead to either more or less cloud cover. Cloud cover (also known as cloudiness, cloudage or cloud amount) refers to the fraction of the Sky obscured by Clouds when observed ^[10] Since on balance cloud cover has a strong cooling effect, any change to the abundance of clouds also affects climate. ^[11]

Monitoring the current status of climate

Testing for spatial dependence between independently measured values in an ordered set is based on applying Fisher’s F-test to the variance of a set and the first variance term of the ordered set. In Mathematical statistics, spatial dependence is a measure for the degree of associative dependence between independently measured values in a temporally or An F-test is any Statistical test in which the test statistic has an F-distribution if the Null hypothesis is true Charting statistically significant variance terms gives a sampling variogram that shows where spatial dependence in our sample space of time dissipates into randomness. In mathematical Statistics, a sampling variogram is a graph that shows where a significant degree of causality (in this context Spatial dependence in sample spaces The lag of a sampling variogram is a statistically robust measure for a change in a climate statistic.

Scientists use "Indicator time series" that represent the many aspects of climate and ecosystem status. In Statistics, Signal processing, and many other fields a time series is a sequence of Data points measured typically at successive times spaced at (often The time history provides a historical context. Current status of the climate is also monitored with climate indices. ^{[12][13][14][15]}

Evidence for climatic change

Evidence for climatic change is taken from a variety of sources that can be used to reconstruct past climates. Most of the evidence is indirect—climatic changes are inferred from changes in indicators that reflect climate, such as vegetation, dendrochronology, ice cores^[16], sea level change, and glacial retreat. Vegetation is a general term for the plant life of a region it refers to the Ground cover provided by plants Dendrochronology (from Greek grc δένδρον dendron, "tree" grc χρόνος khronos, "time" and grc -λογία An ice core is a Core sample from the accumulation of snow and ice over many years that have re-crystallized and have trapped air bubbles from previous time periods Sea-level rise is an increase in Sea level. Multiple complex factors may influence this change

Pollen analysis

Palynology is the science that studies contemporary and fossil palynomorphs, including pollen. Palynology is the science that studies contemporary and fossil Palynomorphs including Pollen, Spores, Dinoflagellate Cysts Acritarchs Palynomorph is the geological term used to describe a particle of a size between five and 500 micrometres found in rock deposits ( Sedimentary rocks and composed of Pollen is a fine to coarse powder consisting of microgametophytes ( pollen grains) which produce the male Gametes (sperm cells of Palynology is used to infer the geographical distribution of plant species, which vary under different climate conditions. Different groups of plants have pollen with distinctive shapes and surface textures, and since the outer surface of pollen is composed of a very resilient material, they resist decay. Pollen is a fine to coarse powder consisting of microgametophytes ( pollen grains) which produce the male Gametes (sperm cells of Changes in the type of pollen found in different sedimentation levels in lakes, bogs or river deltas indicate changes in plant communities; which are dependent on climate conditions^[17][18].

Beetles

Remains of beetles are common in freshwater and land sediments. Beetles are the group of Insects with the largest number of known Species. Different species of beetles tend to be found under different climatic conditions. Knowledge of the present climatic range of the different species, and of the age of the sediments in which remains are found, allows past climatic conditions to be inferred. ^[19]

Glacial geology

Advancing glaciers leave behind moraines and other features that often have datable material in them, recording the time when a glacier advanced and deposited a feature. Moraine refers to any glacially formed accumulation of unconsolidated glacial debris (soil and rock which can occur in currently glaciated and formerly glaciated regions such as those Similarly, by tephrochronological techniques, the lack of glacier cover can be identified by the presence of datable soil or volcanic tephra horizons. Tephrochronology is a geochronological technique that utilises discrete layers of Tephra &mdashvolcanic ash from a single eruption&mdashto create a chronological Tephra is air-fall material produced by a volcanic eruption regardless of composition or fragment size Glaciers are considered one of the most sensitive climate indicators by the IPCC, and their recent observed variations provide a global signal of climate change. See Retreat of glaciers since 1850. whitechuck glacier 2006jpg|right|thumb|320px|The same view as seen in 2006 where this branch of glacier retreated 1

Examples of climate change

Climate change has continued throughout the entire history of Earth. The field of paleoclimatology has provided information of climate change in the ancient past, supplementing modern observations of climate. Paleoclimatology (also Palaeoclimatology) is the study of Climate change taken on the scale of the entire History of Earth.

1. Climate of the deep past
   • Faint young sun paradox
   • Snowball earth
   • Oxygen Catastrophe
2. Climate of the last 500 million years
   • Phanerozoic overview
   • Paleocene–Eocene Thermal Maximum
   • Cretaceous Thermal Maximum
   • Permo–Carboniferous Glaciation
   • Ice ages
3. Climate of recent glaciations
   • Dansgaard–Oeschger event
   • Younger Dryas
   • Ice age temperatures
4. Recent climate
   • Holocene Climatic Optimum
   • Medieval Warm Period
   • Little Ice Age
   • Year Without a Summer
   • Temperature record of the past 1000 years
   • Global warming
   • Hardiness Zone Migration

Climate change and biodiversity

The life cycles of many wild plants and animals are closely linked to the passing of the seasons; climatic changes can lead to interdependent pairs of species (e. The faint young Sun paradox or the faint young Sun problem describes the apparent contradiction between observations of liquid Water early in the Earth's history The Snowball Earth Hypothesis as it was originally proposed]] Evidence The Snowball Earth hypothesis was originally devised to explain the apparent presence of The Oxygen Catastrophe was a massive environmental change believed to have happened during the Siderian period at the beginning of the Paleoproterozoic The Paleocene /Eocene boundary, was marked by the most rapid and significant climatic disturbance of the Cenozoic Era. The Permo-Carboniferous refers to the time period including the latter parts of the Carboniferous and early part of the Permian period An ice age is a period of long-term reduction in the Temperature of the Earth 's surface and atmosphere resulting in an expansion of continental Ice sheets Dansgaard - Oeschger events are rapid climate fluctuations occurring every ≈1470 (± 532 years throughout the Last glacial period. The Younger Dryas Stadial, named after the alpine / tundra wildflower Dryas octopetala, and also referred to as the Big Freeze, was a brief (approximately The Holocene Climate Optimum was a warm period during roughly the interval 9000 to 5000 years B The Medieval Warm Period (MWP or Medieval Climate Optimum was a time of unusually Warm Climate in the North Atlantic region lasting from about The Little Ice Age (LIA was a period of cooling occurring after a warmer era known as the Medieval Warm Period or Medieval Climate Optimum The Year Without a Summer, also known as the Poverty Year, The Year There Was No Summer or Eighteen hundred and froze to death The temperature record of the past 1000 years describes the reconstruction of temperature for the last 1000 years on the Northern Hemisphere. Global warming is the increase in the average measured temperature of the Hardiness Zone Migration refers to the geographical shifts observed in agricultural Hardiness zones as a result of Climate change. Mutualism is a Biological interaction between individuals of two different Species, where both individuals derive a fitness benefit for example increased g. a wild flower and its pollinating insect) losing synchronization, if, for example, one has a cycle dependent on day length and the other on temperature or precipitation. Day length, or length of day, or length of daytime, refers to the temporal length of a day or 24 hours during which there is daylight In principle, at least, this could lead to extinctions or changes in the distribution and abundance of species. One phenomenon is the movement of species northwards in Europe. A recent study by Butterfly Conservation in the UK^[20], has shown that relatively common species with a southerly distribution have moved north, whilst scarce upland species have become rarer and lost territory towards the south. Butterfly Conservation is an insect conservation organization in the United Kingdom. This picture has been mirrored across several invertebrate groups. Drier summers could lead to more periods of drought^[21], potentially affecting many species of animal and plant. For example, in the UK during the drought year of 2006 significant numbers of trees died or showed dieback on light sandy soils. In Australia, since the early 90s, tens of thousands of flying foxes (Pteropus) have died as a direct result of extreme heat^[22]. Bats of the genus Pteropus, belonging to the Megachiroptera sub-order are the largest Bats in the world Wetter, milder winters might affect temperate mammals or insects by preventing them hibernating or entering torpor during periods when food is scarce. For the ability of certain operating systems see Hibernate (OS feature Hibernation is a state of inactivity and metabolic depression Torpor is a (usually short-term state of decreased physiological activity in an animal usually characterized by a reduced body temperature and rate of metabolism One predicted change is the ascendancy of 'weedy' or opportunistic species at the expense of scarcer species with narrower or more specialized ecological requirements. One example could be the expanses of bluebell seen in many woodlands in the UK. These have an early growing and flowering season before competing weeds can develop and the tree canopy closes. The canopy is one of the uppermost levels of a Forest, below the emergent layer, formed by the Tree crowns Canopy trees refers to the trees Milder winters can allow weeds to overwinter as adult plants or germinate sooner, whilst trees leaf earlier, reducing the length of the window for bluebells to complete their life cycle. Organisations such as Wildlife Trust, World Wide Fund for Nature, Birdlife International and the Audubon Society are actively monitoring and research the effects of climate change on biodiversity and advance policies in areas such as landscape scale conservation to promote adaptation to climate change^[23]. BirdLife International (formerly known as the International Council for Bird Preservation, not to be confused with Birds International) is the international conservation The National Audubon Society is an American non-profit Environmental organization dedicated to conservancy Landscape scale conservation is a concept that has arisen primarily in the UK since the mid-1990s in response to both the challenges of Climate change and a perceived An adaptation is a characteristic of an Organism that has been favored by Natural selection and

See also

• Glossary of climate change
• List of climate change topics

Notes

• Emanuel, K. See also Climate change This article serves as a glossary of climate change terms See also Climate change This is a list of climate change topics. A. (2005) Increasing destructiveness of tropical cyclones over the past 30 years. , Nature, 436; 686-688 ftp://texmex.mit.edu/pub/emanuel/PAPERS/NATURE03906.pdfPDF
• IPCC. (2007) Climate change 2007: the physical science basis (summary for policy makers), IPCC.
• Miller, C. and Edwards, P. N. (ed. )(2001) Changing the Atmosphere: Expert Knowledge and Environmental Governance, MIT Press
• Ruddiman, W. F. (2003) The anthropogenic greenhouse era began thousands of years ago, Climate Change 61 (3): 261-293
• Ruddiman, W. F. (2005) Plows, Plagues and Petroleum: How Humans Took Control of Climate, Princeton University Press
• Ruddiman, W. F. , Vavrus, S. J. and Kutzbach, J. E. (2005) A test of the overdue-glaciation hypothesis, Quaternary Science Review, 24:11
• Schmidt, G. A. , Shindel, D. T. and Harder, S. (2004) A note of the relationship between ice core methane concentrations and insolation GRL v31 L23206

References