Greenhouse effect

The greenhouse effect is a natural process of warming of the atmosphere which intervenes in the radiative Bilan of the Earth. It is due to the Gaz with greenhouse effect (GES) contained in the atmosphere, namely mainly the vapor of Eau (which contributes more to the greenhouse effect), the Carbon dioxide CO2 and the Méthane CH4.

This effect was named thus by analogy with the practice in culture and garden-center to build Serre S, closed spaces whose one or more faces are transparent, letting pass the radiation of the captive Sun and retaining it inside. It is the trapping of the Infrarouge S which involves an increase in the temperature.

Operating process

When the Rayonnement Solaire reaches the Terrestrial atmosphere, a part (approximately 28,3  %) is directly considered (returned towards space), by the Air, the Nuage S white and the clear surface of the Ground (in particular areas white and frozen like the Arctique and the the Antarctic), it is the Albédo. The incidental rays which were not considered towards space are absorbed by the atmosphere (20,7%) and/or terrestrial surface (51  %).

This part of the Rayonnement absorptive by the Earth brings to him Chaleur (energy), which it restores in its turn, the night in particular and in winter, in direction of the atmosphere in the form of infra-red raies, it is the radiation of the black Corps. This radiation is then absorbed partly by gases with greenhouse effect. Then in the third time, this Chaleur is re-emitted in all the directions, in particular towards the Earth.

It is this Rayonnement which turns over towards the Earth which creates the greenhouse effect, it is at the origin of an additional contribution of Chaleur on the terrestrial surface. Without this phenomenon, the average temperature on Earth would fall initially with -18  °C. Then, the Ice extending on the sphere, the terrestrial albedo would increase and the temperature would be probably stabilized with -100°C.

One can regard the atmosphere as a tank of energy. If the greenhouse effect is more effective to retain (makes of it slow down the loss of energy) energy, this tank fills - and the energy stored by terrestrial surface increases.

On average, the energy come from space and received by the Earth and the energy of the Earth emitted towards space are almost equal. If it were not the case, the temperature of surface of the Earth would evolve towards increasingly colder or increasingly hotter. Indeed, if the average exchanges of energy with space are not balanced, there will be a storage or a destocking of energy by the Earth. This imbalance then causes a change of temperature of the atmosphere (see Climate warming).

The greenhouse effect owes its name with the analogy between the terrestrial atmosphere and a greenhouse intended to shelter Plante S. the glazed walls of the greenhouse let enter the visible Rayonnement (which transports the major part of energy Solaire) but reflect (does not let escape) of the infra-red radiations, causes important thermal losses of any body (law of the black Corps). Glass of the greenhouse thus plays a part similar to that of the atmosphere, which contains gases with greenhouse effect.

Gases with greenhouse effect

The Gaz with greenhouse effect are gas components of the atmosphere which contribute to the greenhouse effect. The principal gases with greenhouse effect are the Steam, the Carbon dioxide (CO2), the Méthane (CH4), the nitrous oxide (or Protoxyde of nitrogen, of N2O formula) and the Ozone (O3). The industrial gases with greenhouse effect include the heavy halocarbones (chlorinated Fluorocarbones including CFC, the molecules of HCFC-22 like the Fréon and the Perfluorométhane) and the Hexafluorure of sulfur (SF6).

Approximate contributions to the greenhouse effect of principal gases:

These gases have as a common characteristic to absorb part of the Infra-rouge emitted by the surface of the Earth.

The human activity

The majority of gases with greenhouse effect (GES) are of origin Naturelle. But some of them are only due to the human activity or see their concentration in the atmosphere increasing because of this activity. It is the case in particular of the Ozone (O3), of the Carbon dioxide (CO2) and of the Méthane (CH4).
La proof that the increase in atmospheric CO2 is of human origin makes by isotopic analysis .

Ozone is provided in great quantity by the human industrial activity, whereas CFC still largely used destroy them, the Ozone, with the result that one can note a double Phénomène:

  • an accumulation of ozone in the Troposphere above the industrial areas,
  • a destruction of ozone in the Stratosphere above the poles.

The combustion of the carbon S fossils like the coal, the Lignite, the Oil or the Natural gas (Methane) rejects of CO2 in great quantity in the atmosphere. So that only half is recycled by the Nature, and than other half remains in the atmosphere, which increases the greenhouse effect. One of the branches of industry which emits the most gas with greenhouse effect is the energy: on this subject, to see the article energy and greenhouse effect.

The human activities thus release an abundance of GES: the scientists who study the climate think that the increase in the contents of native gas Anthropique is at the origin of a Climate warming. These gases with greenhouse effect thus function as a cover which maintains a hot Température on the surface of our Ground and thus prevent it from cooling.

In France, according to the Group Factor 4, the emissions of Gaz to greenhouse effect come from the Transport S for 26%, followed Industrie (22%), Agriculture (19%), buildings and dwellings (19%), production and transformation of the energy (13%), and treatment of the Déchet S (3%). Since 1990, the emissions increased of more than 20% for transport and the buildings. On the other hand, they decreased by 22% in the Industrie, of 10% in the agricultural sector, 9% in the energy sector and of 8% for the waste processing. (See the draft report 2006 of the Group Factor 4).

Consequences for the environment

The greenhouse effect is not in oneself harmful with the ecosystem s  ; without him, the terrestrial temperature would border the -18  °C. However an excess of GES exceeding the capacity of the ecosystems to trap them and absorb them is a danger to the majority of the species known as advanced .

A total warming would cause initially a mechanical increase in the volume of Sea water by Dilatation and the cast iron of the polar icecaps, which would absorb the low grounds (the coral islands as the islands Maldives are the threatened first), putting in many danger Espèce S of which perhaps, by acidification of the oceans, the Phytoplancton which produces 80  % of the Dioxygène that we breathe and who absorbs the essence of the Carbon dioxide) dissolved in the sea water (CO2 is 60 times more present in the sea than in the air (1,8  % instead of 0,03  %) for a volume coarsely estimated at 1.370 million km ³. Other consequences are awaited, of which an increase in the Pluviométrie, and the modification of the current sailors, which would modify also the mean level of the seas with potentially disastrous consequences. Consequences more or less difficult to envisage are likely to cause true a Climate change. An effect “  swell of neige  ” car maintained could be started by the cast iron of permafrost with evaporation of hydrates of methane, being added to that which could also be released at sea, like by the increase in forest fires and of floods resulting in the immersed organic matter methanisation, which are factor of warming as much.

The scientists envisage an increase in 1,5  °C with 6  °C for the century to come while supposing that the increase in the rejections of GES continues at the 20 last years rate/rhythm (one did not observe a total deceleration of the emissions, even since Kyoto). A complete stop and immediate of the carbon rejections would however not prevent the average temperature of planet from continuing to increase during several tens to hundreds of years, because certain GES only disappear from the atmosphere very slowly.

Consequences for the human ones

The Climate change can only disturb the human activities, more or less directly. For example, after being itself felt sorry for to be increasingly hot in 2006, the Inuit of the Far North Québécois, obtained a reduction of the tariffs of electricity. In June, the Temperature having reached 31 °C during nearly one week, Larry Watt, well-named the mayor of Kuujjuak, the capital of the Nunavik, order of ten Climatiseur S for the municipal council placed.

The Climate warming seems a reality in the north of the parallel 55e: even if the opinions differ from one specialist to another, the models provide that the Température should increase there by four to seven degrees from here the 22e century and that the level of the Mer S of the polar areas should increase by a half Mètre. From here only 15 years, certain passages of the Arctic Ocean could be navigable four or five months per annum instead of two currently.

History of the concept of greenhouse effect

In the Years 1780, Horace-Bénédict de Saussure measurement heating effects of the Solar Radiation using transparent boxes which it lays out in the valley and at the top of a mountain.

In 1824, Joseph Fourier publishes general Remarques on the temperatures of the terrestrial sphere and by planetary spaces in which it refines the analysis of the Expérience S of Horace-Bénédict de Saussure by concluding “the Température of the ground is increased by the interposition of the atmosphere, because the Chaleur Solaire finds less obstacles to penetrate the Air, being to the state of Lumière, that it does not find any to pass by again in the Air when it is converted into obscure heat”.

The Steam and the Carbon dioxide are identified like the principal persons in charge of this greenhouse effect by John Tyndall in 1861. It suggests whereas a modification of the composition of the atmosphere can have an influence on the evolution of the Climat.

In 1896 Svante August Arrhenius estimates that a doubling of the quantity of Carbon dioxide should increase 4° the average temperature. He hopes thus that the exploitation of the coal will make it possible to push back the next glacial era. The American geologist Thomas Chamberlin will arrive independently at the same conclusions.

The greenhouse effect is at the origin of alarms of the Rapport Brundtland (1972). In France, Jean-Marc Jancovici and Hervé Le Treut popularized the Risque S related to the greenhouse effect since the Années 1980.

Discusses scientific on the origin and the consequences of the greenhouse effect

The studies concerning the Climate warming and its consequences among were provided scientific history interdisciplinary. However, the potential political pressures and consequences for the lobby industrial related to the exploitation of the fossil energies, that the adoption of quotas of carbonic emissions would threaten dangerously, supported the emergence and the development of a scientific counter-current calling into question the Interprétation of the Donnée S.

The type of scientific counter-evaluations brought against the alarmist theories of the origin Anthropique of the Climate warming is subject to deposit, in particular because of the financing of these counter-evaluations by industrial lobbies S, chapeautés by Don Pearlman ( cf . Carbon Club) at the time of the agreements signed in Kyoto.

In the documentary video The Greening off the Planet Earth (diffused in 1988), the Western Fuels Association provides that the doubling of the carbon emissions, such as it is in hand, would allow the increase in cultivable surfaces on planet. The Western Fuels Association also financed the launching of the World Climate Review , whose contents can with difficulty claim to hold independence that claims scientific objectivity.

Certain scientists, while recognizing the changes induced by the rise of water and the need to take measures, reject the current catastrophism. For example in the case of the Maldives, which are coral islands, the Hypothèse according to which the corals would be completely able to raise the islands more quickly than the rise of water is sometimes advanced. Espèce S would then be led to regress or to disappear, while others would appear and develop according to the principles of the Natural selection. The Histoire of the Earth watch indeed that there already was in the past of the periods when it made much hotter and other periods when the weather was much colder, and which each time the Nature found the appropriate responses. Others answer these same arguments that these transformations lasted of the Millénaire S, whereas the Climate change considered would occur on one century or two, which could be too fast so that the Nature can adapt.

The role of the Contrail S or trailed condensation of the Avion S.A. is the subject of a report/ratio (in English) of IPCC but must still be cleared up and controlled, in particular in its bonds with the hole in the Couche of ozone which could induce important feedbacks likely to accelerate the total warming (via the reduction in the capacity natural of the ecosystems to absorb and store carbon).

Greenhouse effect on Venus

The greenhouse effect, as natural process, is also observed on Venus where, with an atmosphere made up with carbon dioxide 96% (CO2), the temperature reaches more 400  °C.

See too

External bonds

  • European emissions compared to the objective of Kyoto
  • interdepartmental Mission with the greenhouse effect
  • Network Action Climate France
  • National observatory on the Effects of Climate warming
  • Realclimate Blog of comment of the recent scientific results animated by scientists.
  • chart on the greenhouse effect
  • How a private individual can fight against the greenhouse effect

Simple: Greenhouse effect Zh-min-nan: Un-sek hāu-èng

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