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Saturday, August 16, 2025

Exile

From Wikipedia, the free encyclopedia
https://en.wikipedia.org/wiki/Exile
Napoleon's Exile on Saint Helena by Franz Josef Sandman (1820)
The First Night in Exile – This painting comes from a series illustrating the Ramayana, a Hindu epic poem. It depicts prince Rama, who is wrongly exiled from his father's kingdom, accompanied only by his wife and brother.
Dante in Exile by Domenico Petarlini

Exile or banishment is primarily penal expulsion from one's native country, and secondarily expatriation or prolonged absence from one's homeland under either the compulsion of circumstance or the rigors of some high purpose. Usually persons and peoples suffer exile, but sometimes social entities like institutions (e.g. the papacy or a government) are forced from their homeland.

In Roman law, exsilium denoted both voluntary exile and banishment as a capital punishment alternative to death. Deportation was forced exile, and entailed the lifelong loss of citizenship and property. Relegation was a milder form of deportation, which preserved the subject's citizenship and property.

The term diaspora describes group exile, both voluntary and forced. "Government in exile" describes a government of a country that has relocated and argues its legitimacy from outside that country. Voluntary exile is often depicted as a form of protest by the person who claims it, to avoid persecution and prosecution (such as tax or criminal allegations), an act of shame or repentance, or isolating oneself to be able to devote time to a particular pursuit.

Article 9 of the Universal Declaration of Human Rights states that "No one shall be subjected to arbitrary arrest, detention or exile."

Internal exile

Internal exile is a form of banishment within the boundaries of one's homeland, but far away from home. An example is the system of Katorga in Russia.

For individuals

History

Banishment was used as a punishment in ancient societies such as Babylon, Greece and Rome. It is stipulated as the punishment for incest with one's daughter in the Code of Hammurabi, for manslaughter in Mosaic law, for murder in Athens according to Draco's homicide law, and for rape according to the ancient Indian text Manusmriti. A special form of banishment known as ostracism was practiced in Athens, in which citizens could vote for the expulsion of any citizen for ten years. Ostracism did not entail the loss of property or citizenship, and the ostracized person could return after ten years without disgrace or further penalty. Banishment was the punishment for a variety of offenses in Ancient Rome. In Roman law, exsilium denoted both voluntary exile and banishment as a capital punishment alternative to death. When allowed as an alternative to death, it was accompanied by an administrative decree called interdictio aquae et ignis ("interdiction of water and fire"), which declared the offender an outlaw, allowing any person who encountered him or her within the borders of the country to kill him or her. Deportation was forced exile, and entailed the lifelong loss of citizenship and property. Relegation was a milder form of deportation, which preserved the subject's citizenship and property. The Tang Code of 7th-century China lists a number of crimes punishable by banishment.

Exile was also imposed as a punishment in many societies in medieval Europe. Germanic peoples such as the Franks and Danes are known to have used it. In England, it can be traced back to the 12th century. At that time, a criminal could be allowed to claim sanctuary in a church; if they confessed to their crimes within forty days and took an oath to leave the country and not return without royal permission, they would be allowed to safely go into exile. This practice was abolished by King James I in 1623. Banishment was also a common punishment in the Netherlands: from 1650 to 1750, at least 97 percent of non-capital sentences passed in Amsterdam included some form of banishment. In 1597, the English parliament empowered magistrates to deport "rogues and vagabonds 'beyond the seas'", and in 1615 James I permitted the pardoning of felons on condition of banishment to the Americas. However, it was only after the passing of the Transportation Act of 1718 that banishment to British colonies overseas, termed "transportation", began to be applied systematically as a punishment for serious crimes. Hundreds of convicts were transported annually to the colonies and sold as servants. About 50,000 people were subjected to the punishment throughout the 18th century, including more than two-thirds of all felons convicted at London's main criminal court, Old Bailey, were transported. The practice of transportation in Britain continued well into the 19th century. France also employed banishment to colonies as a punishment, but on a smaller scale than Britain; it was in use to a limited extent until the mid-20th century. The Russian Empire and Qing China used exile as a means to populate frontier territories. Prison colonies became obsolete as the amount of habitable unsettled territory in the world decreased, and prisons became the normal method for dealing with convicts.

Banishment was frequently used as a punishment in the Thirteen Colonies, but it fell into disfavor under the United States. There is no federal law in the United States controlling banishment as a punishment. In the case Cooper v. Telfair (1800), the US Supreme Court established that legislatures have the right to confiscate the property of and banish individuals who take up arms against the United States. At least one legal scholar has argued that this Supreme Court ruling "offered a definitive ruling on the legality of banishment." However, another scholar has argued that this reasoning cannot be easily used in the case of ordinary offenses, "where the security of the country is not at stake." Some US states allow intrastate banishment, although the practice is rare and its legality and constitutionality in many US jurisdictions has been described as "still an open question" by one scholar. Interstate banishment (i.e., expulsion from one US state to another) has been allowed in the United States only in isolated instances.

International law and contemporary use

Denaturalization, or depriving a person of their citizenship, can be viewed as a modern form of banishment. Denaturalization does not necessarily result in an individual losing the right of legal residence in the country that revokes their citizenship, but it often does. Modern international law severely limits the circumstances under which a person can be deprived of their citizenship. Countries which permit the deprivation of citizenship after a criminal conviction for a serious offense include the Netherlands, Belgium, and France. Most states only allow the deprivation of citizenship if it will not cause the person to become stateless.

Exiled heads of state

In some cases the deposed head of state is allowed to go into exile following a coup or other change of government, allowing a more peaceful transition to take place or to escape justice.

A wealthy citizen who moves to a jurisdiction with lower taxes is termed a tax exile. Creative people such as authors and musicians who achieve sudden wealth sometimes choose this. Examples include the British-Canadian writer Arthur Hailey, who moved to the Bahamas to avoid taxes following the runaway success of his novels Hotel and Airport, and the English rock band the Rolling Stones who, in the spring of 1971, owed more in taxes than they could pay and left Britain before the government could seize their assets. Members of the band all moved to France for a period of time where they recorded music for the album that came to be called Exile on Main Street, the Main Street of the title referring to the French Riviera. In 2012, Eduardo Saverin, one of the founders of Facebook, made headlines by renouncing his U.S. citizenship before his company's IPO. The dual Brazilian/U.S. citizen's decision to move to Singapore and renounce his citizenship spurred a bill in the U.S. Senate, the Ex-PATRIOT Act, which would have forced such wealthy tax exiles to pay a special tax in order to re-enter the United States.

In some cases a person voluntarily lives in exile to avoid legal issues, such as litigation or criminal prosecution. An example of this is Asil Nadir, who fled to the Turkish Republic of Northern Cyprus for 17 years rather than face prosecution in connection with the failed £1.7 bn company Polly Peck in the United Kingdom.

Avoiding violence or persecution, or in the aftermath of war

Examples include:

Euphemism for convict

Exile, government man and assigned servant were all euphemisms used in the 19th century for convicts under sentence who had been transported from Britain to Australia.

For groups, nations, and governments

Nation in exile

When a large group, or occasionally a whole people or nation is exiled, it can be said that this nation is in exile, or "diaspora". Nations that have been in exile for substantial periods include the Israelites by the Assyrian king Sargon II in 720 BCE, the Judeans who were deported by Babylonian king Nebuchadnezzar II in 586 BC, and the Jews following the destruction of the second Temple in Jerusalem in AD 70. Jewish prayers include a yearning to return to Jerusalem and the Land of Israel, such as "Next Year in Jerusalem".

After the Partitions of Poland in the late 18th century, and following the uprisings (like Kościuszko Uprising, November Uprising and January Uprising) against the partitioning powers (Russia, Prussia and Austria), many Poles have chosen – or been forced – to go into exile, forming large diasporas (known as Polonia), especially in France and the United States. The entire population of Crimean Tatars (numbering 200,000 in all) that remained in their homeland of Crimea was exiled on 18 May 1944 to Central Asia as a form of ethnic cleansing and collective punishment on false accusations.

Since the Cuban Revolution, over a million Cubans have left Cuba. Most of these self-identified as exiles as their motivation for leaving the island is political in nature. At the time of the Cuban Revolution, Cuba only had a population of 6.5 million, and was not a country that had a history of significant emigration, it being the sixth largest recipient of immigrants in the world as of 1958. Most of the exiles' children also consider themselves to be Cuban exiles. Under Cuban law, children of Cubans born abroad are considered Cuban citizens. An extension of colonial practices, Latin America saw widespread exile, of a political variety, during the 19th and 20th century. Exiled political groups often develop complex media strategies, including diaspora engagement and investigative reporting, to maintain visibility, mobilise support, and address challenges of operating outside their home country.

Government in exile

During a foreign occupation or after a coup d'état, a government in exile of a such afflicted country may be established abroad. One of the most well-known instances of this is the Polish government-in-exile, a government in exile that commanded Polish armed forces operating outside Poland, and the African-based Free French Forces government of Charles de Gaulle during the German Occupation of Poland and France in WWII. Other post-war examples include the client All Palestine Government established by the Egyptian Kingdom, and the Central Tibetan Administration, commonly known as the Tibetan government-in-exile, and headed by the 14th Dalai Lama.

For inanimate objects

Ivan the Terrible once exiled to Siberia an inanimate object: a bell. "When the inhabitants of the town of Uglich rang their bell to rally a demonstration against Ivan the Terrible, the cruel Czar executed two hundred (nobles), and exiled the Uglich bell to Siberia, where it remained for two hundred years."

Drama

Jason and Medea, by John William Waterhouse, 1907

Exile is an early motif in ancient Greek tragedy. In the ancient Greek world, this was seen as a fate worse than death. The motif reaches its peak on the play Medea, written by Euripides in the fifth century BC, and rooted in the very old oral traditions of Greek mythology. Euripides' Medea has remained the most frequently performed Greek tragedy through the 20th century.

Art

Exiled Klaus Mann as Staff Sergeant of the 5th US Army, Italy 1944
Cover of Anna Seghers' Das siebte Kreuz

After Medea was abandoned by Jason and had become a murderess out of revenge, she fled to Athens and married king Aigeus there, and became the stepmother of the hero Theseus. Due to a conflict with him, she must leave the Polis and go away into exile. John William Waterhouse (1849–1917), the English Pre-Raphaelite painter's famous picture Jason and Medea shows a key moment before, when Medea tries to poison Theseus.

Literature

In ancient Rome, the Roman Senate had the power to declare the exile to individuals, families or even entire regions. One of the Roman victims was the poet Ovid, who lived during the reign of Augustus. He was forced to leave Rome and move away to the city of Tomis on the Black Sea, now Constanța. There he wrote his famous work Tristia (Sorrows) about his bitter feelings in exile. Another, at least in a temporary exile, was Dante.

The German-language writer Franz Kafka described the exile of Karl Rossmann in the posthumously published novel Amerika.

During the period of National Socialism in the first few years after 1933, many Jews, as well as a significant number of German artists and intellectuals fled into exile; for instance, the authors Klaus Mann and Anna Seghers. So Germany's own exile literature emerged and received worldwide credit. Klaus Mann finished his novel Der Vulkan (The Volcano: A Novel Among Emigrants) in 1939 describing the German exile scene, "to bring the rich, scattered and murky experience of exile into epic form", as he wrote in his literary balance sheet. At the same place and in the same year, Anna Seghers published her famous novel Das siebte Kreuz (The Seventh Cross, published in the United States in 1942).

Important exile literature in recent years include that of the Caribbean, many of whose artists emigrated to Europe or the United States for political or economic reasons. These writers include Nobel Prize winners V. S. Naipaul and Derek Walcott as well as the novelists Edwidge Danticat and Sam Selvon.

Save the Arctic

From Wikipedia, the free encyclopedia
A symbolic wet frozen polar bear with live belt, in front of Shell Centre, London, during the campaign in September 2015.

Save the Arctic is a Greenpeace campaign to protect the Arctic, principally by preventing oil drilling and unsustainable industrial fishing in the area completely, surrounded by an Arctic-Environmental economics-Zone. The campaign, begun in 2012, calls for a sanctuary in the uninhabited high seas area around the North Pole, similar to the Protocol on Environmental Protection to the Antarctic Treaty. The campaign aims to begin this process by prompting a United Nations resolution on protection for the Arctic. Due to Russian invasion in Ukraine, world's 13% oil reserves could be a melting point in the Arctic.

Background

The Arctic may contain around 20% of the world's remaining undiscovered oil and gas resources. As most easily extractable fossil fuel reserves have been exploited, and the Arctic ice pack shrinks, governments and oil companies have begun to look for new resources in the Arctic. Given these possible threats, in 2008 the European Parliament proposed opening negotiations on a treaty to protect the Arctic.

Support

Greenpeace began the campaign aiming to take a million signatures supporting the campaign to place on the sea bed at the North Pole in April 2013. At the beginning of 2013, the petition registered over 2.5 million signatures. The petition will be accompanied on the sea bed by a flag designed by young people, in partnership with the Girl Guides and Vivienne WestwoodPaul McCartney, Robert Redford, Alejandro Sanz and Richard Branson are amongst those who support this campaign.

The World Wide Fund for Nature is running a related campaign to protect Arctic polar bear habitat, in partnership with Coca-Cola.

Campaign

Oil companies exploring the Arctic, include RosneftRoyal Dutch Shell, Gazprom, and ExxonMobil.

Royal Dutch Shell

Greenpeace and Avaaz have focused their campaigning at the beginning of 2013 on Royal Dutch Shell, including with the use of a parody website.

In 2010, in the immediate aftermath of the BP Deepwater Horizon oil spill, Greenpeace activists painted "No Arctic Drilling" with spilled BP oil on the side of a ship that Shell planned to use for oil exploration in the Arctic. At the protest, Phil Radford of Greenpeace called for "President Obama [to] ban all offshore oil drilling and call for an end to the use of oil in our cars by 2030."

In July 2014, Greenpeace launched a global boycott campaign to persuade Lego to cease producing toys carrying Shell's logo in response to the oil company's plans to drill for oil in the Arctic. Lego's partnership with Shell dates back to the 1960s, although a fictional oil company called Octan featured as the corporation headed by the villain President Business in The Lego Movie. Lego has used the Octan name since 1992 for its fictitious oil company, branding many filling stations, trucks and race cars.

Gazprom

Greenpeace Arctic Sunrise ship case

After an incident in the Kara Sea with the Russian authorities in August 2013 during a "Save-the-Arctic-banner-action", the Greenpeace-ship Arctic Sunrise again was stopped in the Pechora Sea: On Wednesday 18 September, two Greenpeace activists were arrested, protesting against Arctic oil drilling on the Gazprom platform Prirazlomnaya (de) within the exclusive economic zone. Greenpeace International told on their campaign-website, the activists "were held overnight without charges or legal representation aboard a Russian Coast Guard vessel." On September 19, the Russian Coast Guard "illegally boarded the Greenpeace-ship, while in international waters. 11 warning shots have been fired at Arctic-Sunrise, the activists threatened with knives and guns. 30 activists were arrested, 27 "are being held by the Russian Coast Guard against their will".

Phil Radford, executive director of Greenpeace USA, stated that the reaction of the Russian Coast Guard "was the stiffest response that Greenpeace has encountered from a government since the bombing of the Rainbow Warrior in 1985."

To free their activists and end Arctic drilling, the campaigners claimed to sign a petition to the Russian Ambassadors all over the world, and to send a protest-note to Authorities.

In continuity of the successful campaign to reach the Antarctic-Environmental Protocol, in 2012 and 2013 protests with "Save the Arctic" banners were started. To stop oil- and gas-drilling, industrial fishing and military operations in the Arctic region completely, a "global sanctuary in the high arctic" was demanded from the World leaders at the UN General Assembly: "We want them to pass a UN resolution expressing international concern for the Arctic." A resolution to protect the very vulnerable wildlife and ecosystem. 30 Arctic Sunrise activists were arrested in the Pechora Sea, 19 September 2013, witnessing oil-drilling and protesting at the Gazprom platform Prirazlomnaya by the Russian Coast Guard. Greenpeace members were originally charged with Piracy, then later downgraded to hooliganism, before being dropped altogether following the passage of an amnesty law by the Russian government. Today the Gazprom platform Prirazlomnaya is the only platform in the world which continues drilling, oil extraction, and storage operations. Though the project has been heavily criticized by environmental groups there have never happened serious emergencies. The platform is compliant with the most stringent safety requirements. There are walls of caisson between the well and the sea. Spill of oil and petroleum products from the well into the sea is excluded.

Criticism

The campaign has been criticised for not accounting for the legal differences in ownership between Antarctica and the Arctic.

General circulation model

 


From Wikipedia, the free encyclopedia
Climate models are systems of differential equations based on the basic laws of physics, fluid motion, and chemistry. To "run" a model, scientists divide the planet into a 3-dimensional grid, apply the basic equations, and evaluate the results. Atmospheric models calculate winds, heat transfer, radiation, relative humidity, and surface hydrology within each grid and evaluate interactions with neighboring points.

A general circulation model (GCM) is a type of climate model. It employs a mathematical model of the general circulation of a planetary atmosphere or ocean. It uses the Navier–Stokes equations on a rotating sphere with thermodynamic terms for various energy sources (radiation, latent heat). These equations are the basis for computer programs used to simulate the Earth's atmosphere or oceans. Atmospheric and oceanic GCMs (AGCM and OGCM) are key components along with sea ice and land-surface components.

GCMs and global climate models are used for weather forecasting, understanding the climate, and forecasting climate change.

Atmospheric GCMs (AGCMs) model the atmosphere and impose sea surface temperatures as boundary conditions. Coupled atmosphere-ocean GCMs (AOGCMs, e.g. HadCM3, EdGCM, GFDL CM2.X, ARPEGE-Climat) combine the two models. The first general circulation climate model that combined both oceanic and atmospheric processes was developed in the late 1960s at the NOAA Geophysical Fluid Dynamics Laboratory AOGCMs represent the pinnacle of complexity in climate models and internalise as many processes as possible. However, they are still under development and uncertainties remain. They may be coupled to models of other processes, such as the carbon cycle, so as to better model feedback effects. Such integrated multi-system models are sometimes referred to as either "earth system models" or "global climate models."

Versions designed for decade to century time scale climate applications were created by Syukuro Manabe and Kirk Bryan at the Geophysical Fluid Dynamics Laboratory (GFDL) in Princeton, New Jersey. These models are based on the integration of a variety of fluid dynamical, chemical and sometimes biological equations.

Terminology

The acronym GCM originally stood for General Circulation Model. Recently, a second meaning came into use, namely Global Climate Model. While these do not refer to the same thing, General Circulation Models are typically the tools used for modeling climate, and hence the two terms are sometimes used interchangeably. However, the term "global climate model" is ambiguous and may refer to an integrated framework that incorporates multiple components including a general circulation model, or may refer to the general class of climate models that use a variety of means to represent the climate mathematically.

Atmospheric and oceanic models

Atmospheric (AGCMs) and oceanic GCMs (OGCMs) can be coupled to form an atmosphere-ocean coupled general circulation model (CGCM or AOGCM). With the addition of submodels such as a sea ice model or a model for evapotranspiration over land, AOGCMs become the basis for a full climate model.

Structure

General Circulation Models (GCMs) discretise the equations for fluid motion and energy transfer and integrate these over time. Unlike simpler models, GCMs divide the atmosphere and/or oceans into grids of discrete "cells", which represent computational units. Unlike simpler models which make mixing assumptions, processes internal to a cell—such as convection—that occur on scales too small to be resolved directly are parameterised at the cell level, while other functions govern the interface between cells.

Three-dimensional (more properly four-dimensional) GCMs apply discrete equations for fluid motion and integrate these forward in time. They contain parameterisations for processes such as convection that occur on scales too small to be resolved directly.

A simple general circulation model (SGCM) consists of a dynamic core that relates properties such as temperature to others such as pressure and velocity. Examples are programs that solve the primitive equations, given energy input and energy dissipation in the form of scale-dependent friction, so that atmospheric waves with the highest wavenumbers are most attenuated. Such models may be used to study atmospheric processes, but are not suitable for climate projections.

Atmospheric GCMs (AGCMs) model the atmosphere (and typically contain a land-surface model as well) using imposed sea surface temperatures (SSTs). They may include atmospheric chemistry.

AGCMs consist of a dynamical core that integrates the equations of fluid motion, typically for:

  • surface pressure
  • horizontal components of velocity in layers
  • temperature and water vapor in layers
  • radiation, split into solar/short wave and terrestrial/infrared/long wave
  • parameters for:

A GCM contains prognostic equations that are a function of time (typically winds, temperature, moisture, and surface pressure) together with diagnostic equations that are evaluated from them for a specific time period. As an example, pressure at any height can be diagnosed by applying the hydrostatic equation to the predicted surface pressure and the predicted values of temperature between the surface and the height of interest. Pressure is used to compute the pressure gradient force in the time-dependent equation for the winds.

OGCMs model the ocean (with fluxes from the atmosphere imposed) and may contain a sea ice model. For example, the standard resolution of HadOM3 is 1.25 degrees in latitude and longitude, with 20 vertical levels, leading to approximately 1,500,000 variables.

AOGCMs (e.g. HadCM3, GFDL CM2.X) combine the two submodels. They remove the need to specify fluxes across the interface of the ocean surface. These models are the basis for model predictions of future climate, such as are discussed by the IPCC. AOGCMs internalise as many processes as possible. They have been used to provide predictions at a regional scale. While the simpler models are generally susceptible to analysis and their results are easier to understand, AOGCMs may be nearly as hard to analyse as the climate itself.

Grid

The fluid equations for AGCMs are made discrete using either the finite difference method or the spectral method. For finite differences, a grid is imposed on the atmosphere. The simplest grid uses constant angular grid spacing (i.e., a latitude/longitude grid). However, non-rectangular grids (e.g., icosahedral) and grids of variable resolution are more often used. The LMDz model can be arranged to give high resolution over any given section of the planet. HadGEM1 (and other ocean models) use an ocean grid with higher resolution in the tropics to help resolve processes believed to be important for the El Niño Southern Oscillation (ENSO). Spectral models generally use a Gaussian grid, because of the mathematics of transformation between spectral and grid-point space. Typical AGCM resolutions are between 1 and 5 degrees in latitude or longitude: HadCM3, for example, uses 3.75 in longitude and 2.5 degrees in latitude, giving a grid of 96 by 73 points (96 x 72 for some variables); and has 19 vertical levels. This results in approximately 500,000 "basic" variables, since each grid point has four variables (u,v, T, Q), though a full count would give more (clouds; soil levels). HadGEM1 uses a grid of 1.875 degrees in longitude and 1.25 in latitude in the atmosphere; HiGEM, a high-resolution variant, uses 1.25 x 0.83 degrees respectively. These resolutions are lower than is typically used for weather forecasting. Ocean resolutions tend to be higher, for example, HadCM3 has 6 ocean grid points per atmospheric grid point in the horizontal.

For a standard finite difference model, uniform gridlines converge towards the poles. This would lead to computational instabilities (see CFL condition) and so the model variables must be filtered along lines of latitude close to the poles. Ocean models suffer from this problem too, unless a rotated grid is used in which the North Pole is shifted onto a nearby landmass. Spectral models do not suffer from this problem. Some experiments use geodesic grids and icosahedral grids, which (being more uniform) do not have pole-problems. Another approach to solving the grid spacing problem is to deform a Cartesian cube such that it covers the surface of a sphere.

Flux buffering

Some early versions of AOGCMs required an ad hoc process of "flux correction" to achieve a stable climate. This resulted from separately prepared ocean and atmospheric models that each used an implicit flux from the other component different than that component could produce. Such a model failed to match observations. However, if the fluxes were 'corrected', the factors that led to these unrealistic fluxes might be unrecognised, which could affect model sensitivity. As a result, the vast majority of models used in the current round of IPCC reports do not use them. The model improvements that now make flux corrections unnecessary include improved ocean physics, improved resolution in both atmosphere and ocean, and more physically consistent coupling between the atmosphere and ocean submodels. Improved models now maintain stable, multi-century simulations of surface climate that are considered to be of sufficient quality to allow their use for climate projections.

Convection

Moist convection releases latent heat and is important to the Earth's energy budget. Convection occurs on too small a scale to be resolved by climate models, and hence it must be handled via parameters. This has been done since the 1950s. Akio Arakawa did much of the early work, and variants of his scheme are still used, although a variety of different schemes are now in use. Clouds are also typically handled with a parameter, for a similar lack of scale. Limited understanding of clouds has limited the success of this strategy, but not due to some inherent shortcomings of the method.

Software

Most models include software to diagnose a wide range of variables for comparison with observations or study of atmospheric processes. An example is the 2-metre temperature, which is the standard height for near-surface observations of air temperature. This temperature is not directly predicted from the model but is deduced from surface and lowest-model-layer temperatures. Other software is used for creating plots and animations.

Projections

Coupled AOGCMs use transient climate simulations to project/predict climate changes under various scenarios. These can be idealised scenarios (most commonly, CO2 emissions increasing at 1%/yr) or based on recent history (usually the "IS92a" or more recently the SRES scenarios). Which scenarios are most realistic remains uncertain.

The 2001 IPCC Third Assessment Report Figure 9.3 shows the global mean response of 19 different coupled models to an idealised experiment in which emissions increased at 1% per year. Figure 9.5 shows the response of a smaller number of models to more recent trends. For the 7 climate models shown there, the temperature change to 2100 varies from 2 to 4.5 °C with a median of about 3 °C.

Future scenarios do not include unknown events – for example, volcanic eruptions or changes in solar forcing. These effects are believed to be small in comparison to greenhouse gas (GHG) forcing in the long term, but large volcanic eruptions, for example, can exert a substantial temporary cooling effect.

Human GHG emissions are a model input, although it is possible to include an economic/technological submodel to provide these as well. Atmospheric GHG levels are usually supplied as an input, though it is possible to include a carbon cycle model that reflects vegetation and oceanic processes to calculate such levels.

Emissions scenarios

In the 21st century, changes in global mean temperature are projected to vary across the world
Projected change in annual mean surface air temperature from the late 20th century to the middle 21st century, based on SRES emissions scenario A1B (credit: NOAA Geophysical Fluid Dynamics Laboratory)

For the six SRES marker scenarios, IPCC (2007:7–8) gave a "best estimate" of global mean temperature increase (2090–2099 relative to the period 1980–1999) of 1.8 °C to 4.0 °C. Over the same time period, the "likely" range (greater than 66% probability, based on expert judgement) for these scenarios was for a global mean temperature increase of 1.1 to 6.4 °C.

In 2008 a study made climate projections using several emission scenarios. In a scenario where global emissions start to decrease by 2010 and then decline at a sustained rate of 3% per year, the likely global average temperature increase was predicted to be 1.7 °C above pre-industrial levels by 2050, rising to around 2 °C by 2100. In a projection designed to simulate a future where no efforts are made to reduce global emissions, the likely rise in global average temperature was predicted to be 5.5 °C by 2100. A rise as high as 7 °C was thought possible, although less likely.

Another no-reduction scenario resulted in a median warming over land (2090–99 relative to the period 1980–99) of 5.1 °C. Under the same emissions scenario but with a different model, the predicted median warming was 4.1 °C.

Model accuracy

SST errors in HadCM3
North American precipitation from various models
Temperature predictions from some climate models assuming the SRES A2 emissions scenario

AOGCMs internalise as many processes as are sufficiently understood. However, they are still under development and significant uncertainties remain. They may be coupled to models of other processes in Earth system models, such as the carbon cycle, so as to better model feedback. Most recent simulations show "plausible" agreement with the measured temperature anomalies over the past 150 years, when driven by observed changes in greenhouse gases and aerosols. Agreement improves by including both natural and anthropogenic forcings.

Imperfect models may nevertheless produce useful results. GCMs are capable of reproducing the general features of the observed global temperature over the past century.

A debate over how to reconcile climate model predictions that upper air (tropospheric) warming should be greater than observed surface warming, some of which appeared to show otherwise, was resolved in favour of the models, following data revisions.

Cloud effects are a significant area of uncertainty in climate models. Clouds have competing effects on climate. They cool the surface by reflecting sunlight into space; they warm it by increasing the amount of infrared radiation transmitted from the atmosphere to the surface. In the 2001 IPCC report possible changes in cloud cover were highlighted as a major uncertainty in predicting climate.

Climate researchers around the world use climate models to understand the climate system. Thousands of papers have been published about model-based studies. Part of this research is to improve the models.

In 2000, a comparison between measurements and dozens of GCM simulations of ENSO-driven tropical precipitation, water vapor, temperature, and outgoing longwave radiation found similarity between measurements and simulation of most factors. However, the simulated change in precipitation was about one-fourth less than what was observed. Errors in simulated precipitation imply errors in other processes, such as errors in the evaporation rate that provides moisture to create precipitation. The other possibility is that the satellite-based measurements are in error. Either indicates progress is required in order to monitor and predict such changes.

The precise magnitude of future changes in climate is still uncertain; for the end of the 21st century (2071 to 2100), for SRES scenario A2, the change of global average SAT change from AOGCMs compared with 1961 to 1990 is +3.0 °C (5.4 °F) and the range is +1.3 to +4.5 °C (+2.3 to 8.1 °F).

The IPCC's Fifth Assessment Report asserted "very high confidence that models reproduce the general features of the global-scale annual mean surface temperature increase over the historical period". However, the report also observed that the rate of warming over the period 1998–2012 was lower than that predicted by 111 out of 114 Coupled Model Intercomparison Project climate models.

Relation to weather forecasting

The global climate models used for climate projections are similar in structure to (and often share computer code with) numerical models for weather prediction, but are nonetheless logically distinct.

Most weather forecasting is done on the basis of interpreting numerical model results. Since forecasts are typically a few days or a week and sea surface temperatures change relatively slowly, such models do not usually contain an ocean model but rely on imposed SSTs. They also require accurate initial conditions to begin the forecast – typically these are taken from the output of a previous forecast, blended with observations. Weather predictions are required at higher temporal resolutions than climate projections, often sub-hourly compared to monthly or yearly averages for climate. However, because weather forecasts only cover around 10 days the models can also be run at higher vertical and horizontal resolutions than climate mode. Currently the ECMWF runs at 9 km (5.6 mi) resolution as opposed to the 100-to-200 km (62-to-124 mi) scale used by typical climate model runs. Often local models are run using global model results for boundary conditions, to achieve higher local resolution: for example, the Met Office runs a mesoscale model with an 11 km (6.8 mi) resolution covering the UK, and various agencies in the US employ models such as the NGM and NAM models. Like most global numerical weather prediction models such as the GFS, global climate models are often spectral models instead of grid models. Spectral models are often used for global models because some computations in modeling can be performed faster, thus reducing run times.

Computations

Climate models use quantitative methods to simulate the interactions of the atmosphere, oceans, land surface and ice.

All climate models take account of incoming energy as short wave electromagnetic radiation, chiefly visible and short-wave (near) infrared, as well as outgoing energy as long wave (far) infrared electromagnetic radiation from the earth. Any imbalance results in a change in temperature.

The most talked-about models of recent years relate temperature to emissions of greenhouse gases. These models project an upward trend in the surface temperature record, as well as a more rapid increase in temperature at higher altitudes.

Three (or more properly, four since time is also considered) dimensional GCM's discretise the equations for fluid motion and energy transfer and integrate these over time. They also contain parametrisations for processes such as convection that occur on scales too small to be resolved directly.

Atmospheric GCMs (AGCMs) model the atmosphere and impose sea surface temperatures as boundary conditions. Coupled atmosphere-ocean GCMs (AOGCMs, e.g. HadCM3, EdGCM, GFDL CM2.X, ARPEGE-Climat) combine the two models.

Models range in complexity:

  • A simple radiant heat transfer model 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.
  • Box models treat flows across and within ocean basins.

Other submodels can be interlinked, such as land use, allowing researchers to predict the interaction between climate and ecosystems.

Comparison with other climate models

Earth-system models of intermediate complexity (EMICs)

The Climber-3 model uses a 2.5-dimensional statistical-dynamical model with 7.5° × 22.5° resolution and time step of 1/2 a day. An oceanic submodel is MOM-3 (Modular Ocean Model) with a 3.75° × 3.75° grid and 24 vertical levels.

Radiative-convective models (RCM)

One-dimensional, radiative-convective models were used to verify basic climate assumptions in the 1980s and 1990s.

Earth system models

GCMs can form part of Earth system models, e.g. by coupling ice sheet models for the dynamics of the Greenland and Antarctic ice sheets, and one or more chemical transport models (CTMs) for species important to climate. Thus a carbon chemistry transport model may allow a GCM to better predict anthropogenic changes in carbon dioxide concentrations. In addition, this approach allows accounting for inter-system feedback: e.g. chemistry-climate models allow the effects of climate change on the ozone hole to be studied.

History

In 1956, Norman Phillips developed a mathematical model that could realistically depict monthly and seasonal patterns in the troposphere. It became the first successful climate model. Following Phillips's work, several groups began working to create GCMs. The first to combine both oceanic and atmospheric processes was developed in the late 1960s at the NOAA Geophysical Fluid Dynamics Laboratory. By the early 1980s, the United States' National Center for Atmospheric Research had developed the Community Atmosphere Model; this model has been continuously refined. In 1996, efforts began to model soil and vegetation types. Later the Hadley Centre for Climate Prediction and Research's HadCM3 model coupled ocean-atmosphere elements. The role of gravity waves was added in the mid-1980s. Gravity waves are required to simulate regional and global scale circulations accurately.

Health effects of sunlight exposure

From Wikipedia, the free encyclopedia
Sunbaker, by Max Dupain

Exposure of skin to ultraviolet radiation from sunlight presents both positive and negative health effects. On the positive side, UV exposure enables the synthesis of vitamin D3, which is essential for bone health[1] and potentially plays a role in inhibiting certain cancers. While vitamin D can also be obtained through dietary supplements, UV exposure offers benefits such as enhanced subdermal nitric oxide production and improved endorphin levels, which are not achievable through supplementation alone. Additionally, exposure to visible light supports melatonin synthesis, maintains circadian rhythms, and reduces the risk of seasonal affective disorder.

However, UV radiation is also a mutagen and carcinogen for the skin, posing significant risks. Acute exposure can lead to painful sunburns and increase the likelihood of developing serious skin conditions later in life. Prolonged exposure is associated with the development of skin cancers, photoaging or premature skin aging, immune suppression, and eye diseases like cataracts.

Given these dual effects, public health organizations emphasize the importance of striking a balance between the benefits and risks of UV exposure. They recommend avoiding sunburn at all costs and advocate for moderation in sun exposure to minimize the risks associated with UV radiation while still reaping its health benefits. That being said, experts encourage avoiding sun exposure between the hours of 10 a.m. to 4 p.m. since this can reduce skin cancer, skin damage, and premature aging.

Vitamin D3 production

Radiograph of a child with rickets, usually caused by insufficient vitamin D

UVB radiation with a wavelength of 290–315 nanometers penetrates uncovered skin and converts cutaneous 7-dehydrocholesterol to previtamin D3, which in turn becomes vitamin D3. UVB radiation does not penetrate glass, so exposure to sunshine indoors through a window does not produce vitamin D. Time of day, time of year, geographic latitude, ground altitude, cloud cover, smog, skin melanin content, and sunscreen are among the factors that greatly affect UV intensity and vitamin D synthesis, making it difficult to provide general guidelines. It has been suggested by some researchers, for example, that adequate amounts of vitamin D can be produced with moderate sun exposure to the face, arms and legs, averaging 5–30 minutes twice per week without sunscreen. (The darker the complexion, or the weaker the sunlight, the more minutes of exposure are needed, approximating 25% of the time for minimal sunburn. Vitamin D overdose is impossible from UV exposure; the skin reaches an equilibrium where the vitamin degrades as fast as it is created.) Individuals with limited sun exposure need to include good sources of vitamin D in their diet or take a supplement.

The only way to quantify adequate levels of vitamin D is with a serum 25(OH)D3 (calcifediol) test. In the United States, serum 25(OH)D3 was below the recommended level for more than a third of white men in a 2005 study, with serum levels even lower in women and in most minorities. This indicates that vitamin D deficiency may be a common problem in the US. Australia and New Zealand have had similar findings, which indicate insufficient protection against rickets for children and osteoporosis for adults.

Over the past several years, levels of ultraviolet radiation have been tracked at over 30 sites across North America as part of the United States Department of Agriculture's UVB Monitoring and Research Program at Colorado State University. The first map at right shows levels of UVB radiation in June 2008, expressed in Vitamin D Equivalents.

UV map (Vitamin D Equivalents)

Using satellite data, measurements from the European Space Agency produce similar maps expressed in units of the widely followed UV Index, for locations around the world. Effects of UV-radiation at high latitudes, where snow stays on the ground into early summer and the sun then remains at a low position even at its zenith, have been reviewed by Meyer-Rochow.

UV map (UV Index)

Exposure to ultraviolet radiation from the sun is a source of vitamin D. One minimal erythemal dose of sunlight UV radiation provides the equivalent of about 20,000 IU of vitamin D2, taken as an oral supplement. If an adult's arms and legs are exposed to a half minimal erythemal UV radiation, it is the same as taking 3,000 IU of vitamin D3 through an oral supplement. This exposure of 10–15 minutes, on a frequency of two to three times per week, will cause the adult's skin to produce enough vitamin D. It is not necessary to expose the face to the UV, as facial skin provides little vitamin D3. Individuals whose metabolism makes taking oral vitamin D ineffective are able, through exposure to an ultraviolet lamp that emits UV-B radiation, to achieve a 25 (OH) D blood level.

Three benefits of UV exposure are production of vitamin D, improvement in mood, and increased energy.

UVB induces production of vitamin D in the skin at rates of up to 1,000 IUs per minute. This vitamin helps to regulate calcium metabolism (vital for the nervous system and bone health), immunity, cell proliferation, insulin secretion, and blood pressure. In low and middle income countries, foods fortified with vitamin D are "practically nonexistent." Most people in the world depend on the sun to get vitamin D, and elderly populations in low UVB countries experience higher rates of cancer.

There are not many foods that naturally have vitamin D. Examples are cod liver oil and oily fish. If people cannot get sunlight, then they will need 1,000 IU of vitamin D per day to stay healthy. A person would have to eat oily fish three or four times per week in order to get enough vitamin D from that food source alone.

People with higher levels of vitamin D tend to have lower rates of diabetes, heart disease, and stroke and tend to have lower blood pressure. However, it has been found that vitamin D supplementation does not improve cardiovascular health or metabolism, so the link with vitamin D must be in part indirect. People who get more sun are generally healthier, and also have higher vitamin D levels. It has been found that ultraviolet radiation (even UVA) produces nitric oxide (NO) in the skin, and nitric oxide can lower blood pressure. High blood pressure increases the risk of stroke and heart disease. Although long-term exposure to ultraviolet contributes to non-melanoma skin cancers that are rarely fatal, it has been found in a Danish study that those who get these cancers were less likely to die during the study, and were much less likely to have a heart attack, than those who did not have these cancers.

People in certain situations, such as people with intellectual disabilities and neurodevelopmental disorders who stay inside most of the time have low vitamin D levels. Getting enough vitamin D can help stave off "autoimmune diseases, cardiovascular disease, many types of cancer, dementia, types 1 and 2 diabetes mellitus, and respiratory tract infections."

Fetuses and children who do not get enough vitamin D can result in "growth retardation and skeletal deformities."

Multiple sclerosis risk

Multiple sclerosis (MS) is least prevalent in the sunniest regions. Exposure to the ultraviolet-B radiation of sunlight appears to be most important and this may operate via vitamin D synthesis.

Effects on skin

Melanoma on human skin
Sunburn peeling

Ultraviolet (UV) irradiation present in sunlight is an environmental human carcinogen. The toxic effects of UV from natural sunlight and therapeutic artificial lamps are a major concern for human health. Skin surface lipids, including unsaturated lipids such as squalene, sebaleic acid, linoleic acid, and cholesterol can be a subject of oxidation by singlet oxygen and ozone as well as free radicals. Ultraviolet radiation activates lipoxygenase and cyclooxygenase, inducing specific enzymatic oxidation of lipids. Free radical mediated lipid peroxidation gives multiple oxidation products which may induce various skin diseases

UVB damages mRNA This triggers a fast pathway that leads to inflamination of the skin and sunburn. mRNA damage initially triggers a response in ribosomes though a protein known as ZAK-alpha in a ribotoxic stress response. This response acts as a cell surveillance system. Following this detection of RNA damage leads to inflammatory signaling and recruitment of immune cells. This, not DNA damage (which is slower to detect) results in UVB skin inflammation and acute sunburn.

The major acute effects of UV irradiation on normal human skin comprise sunburn inflammation erythema, tanning, and local or systemic immunosuppression. The most deadly form, malignant melanoma, is mostly caused by indirect DNA damage from UVA radiation. This can be seen from the absence of a direct UV signature mutation in 92% of all melanoma. UVC is the highest-energy, most-dangerous type of ultraviolet radiation, and causes adverse effects that can variously be mutagenic or carcinogenic.

Despite the importance of the sun to vitamin D synthesis, it is prudent to limit the exposure of skin to UV radiation from sunlight and from tanning beds. According to the National Toxicology Program Report on Carcinogens from the US Department of Health and Human Services, broad-spectrum UV radiation is a carcinogen whose DNA damage is thought to contribute to most of the estimated 1.5 million skin cancers and the 8,000 deaths due to metastatic melanoma that occur annually in the United States. The use of sunbeds is reported by the World Health Organization to be responsible for over 450,000 cases of non-melanoma skin cancer and over 10,000 cases of melanoma every year in the U.S., Europe, as well as Australia. Lifetime cumulative UV exposure to skin is also responsible for significant age-associated dryness, wrinkling, elastin and collagen damage, freckling, IGH, age spots and other cosmetic changes. The American Academy of Dermatology advises that photoprotective measures be taken, including the use of sunscreen, whenever one is exposed to the sun. Short-term over-exposure causes the pain and itching of sunburn, which in extreme cases can produce more-severe effects like blistering.

Several countries (such as Australia) provide public forecasts of UV irradiation in the form of the UV Index. The index can be used as a guide to the public of dangers from over-exposure to sunlight, especially around noon, when direct sunlight is at its most intense.

Effects on eyes

Prolonged optical exposure to sunlight, especially intense ultraviolet light, may be linked to cortical cataracts, and high levels of visible light is maybe linked to macular degeneration.

However, significant daily exposure to bright light may be necessary for children to avoid myopia (nearsightedness).

Short-term over-exposure can cause snow blindness, which is analogous to sunburn of the cornea, or can cause solar retinopathy, which is long-lasting retinal damage and vision impairment from sungazing.

Frequent exposure to the sun can cause yellow non-cancerous bumps on the middle part of the sclera of the eye, called pingueculae. It is most common in younger people, mainly those who spend a lot of their time outdoors and do not protect their eyes from UV rays. To decrease the risk of developing pingueculae, it may be wise to wear sunglasses when outdoors, even on overcast days.

Circadian rhythm

Light to the eyes, primarily blue-wavelength light, is important for the entrainment and maintenance of robust circadian rhythms. Exposure to sunlight in the morning is particularly effective; it leads to earlier melatonin onset in the evening and makes it easier to fall asleep. Natural daylight exposure, particularly at high intensities, has been shown to have numerous beneficial effects on sleep patterns. It can advance sleep timing (leading to earlier bedtimes), affect sleep duration, and improve overall sleep quality. Bright morning light has been shown to be effective against insomnia, premenstrual syndrome and seasonal affective disorder (SAD).

Folate degradation

Blood levels of folate, a nutrient vital for fetal development, can be degraded by UV radiation, raising concerns about sun exposure for pregnant women. Lifespan and fertility can be adversely affected for individuals born during peaks of the 11-year solar cycle, possibly because of UV-related folate deficiency during gestation.

Blood pressure

A seasonal variation in blood pressure has been noted for decades. Research indicates that skin exposure to sunlight results in a modest reduction in systolic blood pressure. The effect is independent of vitamin D status, instead being mediated by nitric oxide release from skin upon exposure to UV light. The effect is greater in fair-skinned individuals.

Cognitive functioning and mood

UV exposure plays a role in motor learning and object recognition memory. Moderate UV exposure enhances cognitive functioning through a specialized glutamate (GLU) biosynthetic pathway in the brain. The process begins when UV exposure triggers an increase in blood levels of urocanic acid (UCA), which possesses the unique ability to cross the blood-brain barrier. Upon entering the brain, UCA initiates a cascade of biochemical reactions that promote glutamate biosynthesis, particularly in critical regions such as the motor cortex and hippocampus. This increased glutamate production leads to notable cognitive enhancements, including improved motor learning capabilities, enhanced object recognition memory, and strengthened synaptic plasticity.

Ultraviolet (UV) light has been shown to influence various neurological functions, including mood, addiction, cognition, and memory. This impact likely occurs through UV-induced changes in brain chemistry, potentially altering neurotransmitter systems and neuroplasticity. UV exposure might, for example, affect serotonin levels, which play a significant role in mood regulation and cognitive functions. This hormonal effect can helps stabilize circadian rhythms. This stabilizing effect is particularly important for individuals with mental disorders, who often experience circadian desynchronization and sleep problems. As a result, light therapy has emerged as an increasingly popular treatment option for various mood and psychiatric disorders.

Safe level of sun exposure

According to a 2007 study submitted by the University of Ottawa to the US Department of Health and Human Services, there is not enough information to determine a safe level of sun exposure that imposes minimal risk of skin cancer. In addition, there is not yet conclusive evidence on which components of ultraviolet radiation (UVA, UVB, UVC) are actually carcinogenic. UVC is almost completely absorbed by the atmosphere and does not reach the surface in any appreciable quantity. As a result, only the broad-spectrum combination (UVA, UVB, UVC) known as "ultraviolet radiation" is listed as a carcinogen; the components are only "likely to become" known carcinogens. Solar radiation (sunlight) and sunlamps are listed as carcinogens because they contain ultraviolet radiation.

Lifetime sun exposure

Map of human skin color distribution for native populations, by R. Biassutti in Von Luschan's chromatic scale for classifying skin color. It was reported that for areas with no data Biasutti simply filled in the map by extrapolation from findings obtained in other areas.

In 2007, there were no recommendations on a safe level of total lifetime sun exposure. According to epidemiologist Robyn Lucas at Australian National University, analysis of lifespan versus disease shows that far more lives worldwide could be lost to diseases caused by lack of sunlight than to those caused by too much, and it is inappropriate to recommend total avoidance of sunlight.

Over thousands of years, in many climate zones, genetic selection has helped indigenous human populations adapt toward skin pigmentation levels that provide a healthy level of UV exposure. This largely explains the tendency toward darker-skinned populations in the sunniest tropical environments, and lighter skin tones in less-sunny regions and for those who most need vitamin D for rapid bone growth, specifically children and reproductive-age women. The map to the right illustrates the geographic distribution of skin color for native populations prior to 1940, based on von Luschan's chromatic scale. These long-term adaptations for optimal health can be confounded by patterns of food, clothing and shelter, especially at a time when large populations have migrated far from the climates for which their skin was genetically adapted.

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