Greenhouse gas

Greenhouse gases are gaseous radiation- influencing substances in the air that contribute to the greenhouse effect and may be natural or anthropogenic origin can. They absorb some of the infrared radiation emitted by the soil that would otherwise escape into space. According to their temperature emit thermal radiation (infrared radiation), which directed toward the earth fraction additionally heated as atmospheric counter-radiation the Earth's surface to sunlight. The natural greenhouse gases raise the average temperature at the Earth's surface to about 33 ° C to 15 ° C. Without this natural greenhouse effect, the lower atmosphere would have, which would make life on Earth almost impossible by a global average only -18 ° C.

The disturbance of the natural balance of the atmosphere by interfering with the natural environment and by anthropogenic emissions of greenhouse gases enhance the natural greenhouse effect and causes global warming, which in turn is associated with numerous consequences.

The increase, that is, in the atmosphere increasing content of certain greenhouse gases is largely attributed to human activities.

In November 2008, the UN Climate Change Secretariat announced that greenhouse gas emissions have risen by 2.3 % in acquired 40 industrial countries between 2000 and 2006, and urged an urgent need for action on the policy.

• 2.1 Water vapor
• 2.2 ozone
• 2.3 Cloud
• 2.4 Aerosols and soot

• 5.1 Germany
• 5.2 Worldwide

Greenhouse gases under the Kyoto Protocol

By far the most greenhouse gases per capita are ejected in the industrialized nations. The comparison must be taken into account that in countries with colder climate caused by the heating of more greenhouse gases than in countries with a warmer climate. In order to slow climate change, at least, so it must be done for reducing the emission of greenhouse gases, especially in the first world much more.

In the Kyoto Protocol, a legally binding international agreement to reduce the anthropogenic emissions of key greenhouse gases (direct greenhouse gas ) was decided. Other greenhouse gases, the so-called indirect greenhouse gases, such as carbon monoxide ( CO), nitrogen oxides ( NOx) or volatile non-methane hydrocarbons, so-called NMVOCs are regulated by the Montreal Protocol because they contribute to ozone depletion.

The U.S. refuses to date a signing of the Kyoto Protocol. In California, it was decided on 30 August 2006 to bring CO2 emissions back to 2020 levels by 1990.

In the Kyoto Protocol have been included as these in the atmosphere have high global warming potential due to their high retention in addition to the above-mentioned greenhouse gases Fluorinated greenhouse gases ( F- gases).

The regulated by the Kyoto Protocol gases are: carbon dioxide (CO2 serves as a reference value ), methane ( CH4), nitrous oxide (laughing gas, N2O), hydrofluorocarbons and sulfur hexafluoride ( SF6). Since 2012, nitrogen trifluoride ( NF3 ) is regulated as an additional greenhouse gas.

Carbon dioxide

Carbon dioxide ( CO2) is present in an amount of about 0.039 % ( 400 ppm, Booth 2013) in the atmosphere and accounts for 9-26 % of the natural greenhouse effect.

The geogenic, ie natural CO2 production is approximately 550 Gt per year. This is offset by the carbon cycle, an almost equally high natural consumption, especially by photosynthesis, but also by binding in calcifying organisms.

Carbon dioxide is produced, inter alia, by the combustion of fossil fuels ( by traffic, heating, electricity, industry). His average atmospheric residence time is about 120 years. The global anthropogenic CO2 emissions in 2006 amounted to about 32 gigatonnes (Gt ) and accounts for about 60 % of human-induced enhanced greenhouse effect from.

The emissions from human activity have caused an increase the concentration of CO2 in the atmosphere since the industrial revolution of 280 ppm by almost 40% to 390 ppm ( 2011). Thus, the current concentration is higher than in the last 800,000 years, and probably higher than in the last 20 million years.

A number of course taking place processes contribute to the decrease in the atmospheric concentration of carbon dioxide; the anthropogenic increase in the concentration can only be compensated for periods of hundreds and tens of thousands. These processes can be running since the mid-19th century rise in CO2 concentration is only damp, but not compensate. The degree of binding of additional carbon dioxide evolved is a factor of uncertainty in the parameterization of climate models.

The increased uptake by terrestrial and marine plants is the fastest-acting mechanism that dampens the rise in atmospheric gas concentration and directly affects. Thus, it was twice as much carbon dioxide absorbed in 2010 by the biosphere as in 1960, while the emission rate but quadrupled.

The second fastest mechanism is the dissolution of the gas in seawater, a process which acts over a period of centuries, as the oceans take a long time to blend together. Although the solution of a portion of the additional carbon dioxide in the ocean absorbs the greenhouse effect, but through the formation of carbonic acid to lower pH of the water ( ocean acidification ). It follows the reaction of acidic sea water with the lime of the ocean sediments. Carbon dioxide is thus withdrawn from circulation over a period of thousands of years. The slowest -acting response is the weathering of rocks, a process that extends over hundreds of thousands of years. Climate simulations suggest that the heated by an increased concentration of carbon dioxide earth will cool down only by about one degree per 12,000 years because of the long time constant of the latter processes.

Methane

Methane ( CH4) comes only in trace amounts in the atmosphere (<2 ppm). Anthropogenic Methane is about one half in the agriculture, forestry and other uses of land and biomaterial in animal production, wastewater treatment plants and landfills. The other half will be free by the industry due to leaks in production, transportation and processing of natural gas and especially by the incomplete combustion during flaring of technically recoverable gas. Methane is also from many non-flowing bodies of water (eg rice fields ) are released. Organic matter is the fact of microorganisms (eg Archaeabakterien ) anaerobically digested gases (mainly methane ) is decomposed. An indirect effect is the release of the further thawing of permafrost. Another such source is in large quantities and in the continental margins undersea superposing methane hydrate, a solid which decomposes on heating into methane and water.

Methane contributes due to its high efficiency (25 times as effective as CO2 ), with approximately 20 % to the anthropogenic greenhouse effect. The residence time in the atmosphere is much shorter than for CO2 with 9 to 15 years. From the world's anthropogenic methane emitted amount ( about 5.9 Gt of CO2 equivalent ) originate about 37 % directly or indirectly from livestock farming. Of these supplies most from fermentation processes in the stomach of ruminants.

The global average methane content of the atmosphere has increased to 1,750 ppb in 1999 since pre-industrial times (1750 ) of around 600 ppb. In the period from 1999 to 2006, the methane content of the atmosphere has remained largely constant, but increases significantly since 2007 to over 1800 ppb. There is so much more methane in the atmosphere than ever during the last 650,000 years. During this time, the methane content ranged 320-790 ppb, was detected from ice cores as the basis.

Nitrous oxide ( laughing gas)

Nitrous oxide ( N2O) is a greenhouse gas whose greenhouse effects is 298 times as large as that of CO2. Man-made emissions come mainly from agriculture ( livestock, fertilizers and cultivation of legumes, biomass), medical technology and less from fossil-fueled power plants and traffic. The main source of N2O are microbial degradation processes of nitrogen compounds in the soil. These take place both under natural conditions and by Nitrogen from agriculture, industry and transport. Nitrous oxide formation is a relatively unexplored frontier still insufficient. However, it is known that especially with heavy, over-fertilized and moist soils particularly much N2O escapes into the air. Also, the precipitation of ammonium - nitrogen from the air, resulting from manure evaporations, may contribute to the formation of nitrous oxide.

With a mean atmospheric residence time of 114 years and a relatively high global warming potential, there is a climate- relevant gas. The reduction of N2O is essentially performed by reaction with sunlight in the stratosphere. The volume fraction increased from pre-industrial 270 ppbv around 20 % to 322-323 ppbv (2010). His contribution to the anthropogenic greenhouse effect is about 5-6% today.

N2O also plays a role in processes in the ozone layer, which in turn contribute to the greenhouse effect: for example, catalyzed by halogen radicals cleavage of ozone in the lower stratosphere leads to a series of chemical processes in which methane, hydrogen and volatile organic substances are oxidized. N2O is particularly important in cold and darkness able to form with the radicals so-called reservoir species, which the radicals are temporarily ineffective for ozone depletion (see ozone hole ).

Fluorocarbons

While the classic greenhouse gas usually formed as unwanted by-products are produced specifically for the most part and used as a propellant, cold or fire extinguishing agent fluorocarbons and chlorofluorocarbons (CFCs ). To reduce these substances, therefore, especially the development of substitutes is required in addition to technical measures. Today they are used in a similar manner as before since 1995 only limited usable chlorofluorocarbon substances that are not only responsible for the destruction of the ozone layer, but also have a strong impact on climate. Fluorocarbons currently contribute about 10 % to global warming. Some of which are up to 14,800 times more potent than carbon dioxide, air. With a further increase could boost the greenhouse effect in addition massively.

The fluorocarbons between the partially halogenated fluorocarbons ( HFCs) and the fully halogenated fluorocarbons ( HFCs) are distinguished. Are HFCs completely fluorinated (ie no more hydrogen atoms), called this also perfluorinated fluorocarbons (PFC ).

Tetrafluoromethane (CF4 ) in the atmosphere is partially of natural origin. Larger emissions come from the production of primary aluminum. Ethane and propane derivatives ( C2, C3) of the fluorinated hydrocarbons are used as the refrigerant. Some higher molecular weight fluorinated hydrocarbons (C6 - C8 ) can be used as a cleaner. In addition, PFCs are used in the plastics and polymer industry on a large scale as starting materials for the production of fluorinated plastics, oils, greases and other chemicals ( the production is often done via a CFC- precursor) used in the electronics and screen industry as an etching gas and v. a. m.

In the European F- Gas Regulation ( published June 14, 2006) and the transposition into national law by the chemicals Climate Protection Ordinance ( ChemKlimaschutzV ) measures to reduce emissions from refrigeration systems have been made. This is in contrast to the CFC- Halon Prohibition Ordinance is not a prohibition on use, but by higher requirement to the execution and maintenance of refrigeration systems to be reduced released through leaks quantities. In the period from 2008 to 2012, they are to be reduced by 8 % over the 1990 level. In addition, the use of fluorinated greenhouse gases for certain activities on certain dates ( July 4, 2006, July 4, 2007 July 4, 2008 and 4 July 2009) is no longer permitted.

The content of fluorocarbons in the atmosphere is constant since 1999 or even partially takes off again.

Sulfur hexafluoride and nitrogen trifluoride

According to studies by the Intergovernmental Panel on Climate Change (IPCC), sulfur hexafluoride SF6 is the most potent known greenhouse gas. The mean residence time of SF6 in the atmosphere is 3200 years. Its global warming potential is 22,800 times as high as that of carbon dioxide ( CO2). Due to the very low concentration of SF6 in the atmosphere ( approximately 0.005 ppb by volume, which corresponds to 0.12 ppmv CO2 equivalent; CO2 390 ppm), however, is its impact on global warming low.

Sulfur hexafluoride, SF6 is used as an insulating gas or quenching gas in high voltage switchgear and used as an etching gas in semiconductor industry. Until about 2000, it was also used as a filler gas for car tires and as a filler gas in soundproof insulating glass panes; the use of sulfur hexafluoride as tire filling has been banned since July 4, 2007. An important role has the gas in the production of magnesium. It prevents the hot molten metal comes into contact with the air. Due to the process escape in this application larger quantities into the atmosphere, therefore alternative shielding gases are investigated.

In addition, there are other powerful greenhouse gases, such as nitrogen trifluoride, whose greenhouse effect is 17,200 times greater than that of CO2. In 2008, the Earth's atmosphere contained 5400 tons of nitrogen trifluoride.

Further contributing to the greenhouse effect substances

Water vapor

Water vapor is the main greenhouse gas. His contribution to the natural greenhouse effect is estimated to be about 60%. He comes predominantly from the water cycle ( ocean - evaporation - precipitation - storage in the soil ) plus a small percentage from the volcanism.

Man indirectly increases the water vapor content in the atmosphere, because the air temperature rise and thus the evaporation rate due to global warming. It is the most important global warming reinforcing feedback factor.

In the stratosphere, water vapor occurs only in traces; he comes z.T. from air traffic and from the decay of methane to CO2 and H2O, and contributes to the greenhouse effect.

Ozone

Ozone is also a climate- relevant gas, which is, however, not directly, but only indirectly influenced by man.

The ozone layer is located in the stratosphere above the tropopause, ie in a layer in which occurs no more water. The stratosphere has by the ozone absorbs the UV radiation from the sun, an inverse temperature profile, ie the air warms up here with increasing height. This distinguishes them from the enclosing them air layers. The strongest is the heating in the ozone layer, where the temperature rises from -60 ° C up to just below 0 ° C to. If this ozone layer damaged, gets more energetic ultraviolet radiation to the surface.

The highest density of ozone is in good 20-30 km altitude, the highest volume fraction of about 40 km altitude. Would you everything ozone, which is located in the atmosphere, extract and compress to normal pressure, would the a 3 mm thick layer on the surface. For comparison, the column of air with the other gases (mainly nitrogen and oxygen) would be the power of 8 km.

The stratospheric ozone layer is not to be confused with the ground-level ozone. This is formed from different precursors (nitrogen oxides, hydrocarbons, carbon monoxide ) under sunlight (summer smog). It is harmful in higher concentrations.

Clouds

Clouds, so condensed water vapor are, strictly speaking, not a greenhouse gas. However, they also absorb infrared radiation and thereby enhance the greenhouse effect. At the same time clouds also reflect part of the incident solar energy and thus also have a cooling effect. Which effect is predominant, depends on factors such as the level, time of day / sun altitude, density, or geographical position of the clouds. The extent to which global warming the total cooling in the current climate effect of clouds attenuates or amplifies is the least secure feedback effect of the current global warming.

Aerosols and particulates

Aerosols are solid or liquid particles in the air and reach by human activity into the atmosphere. These include particles from diesel exhaust and combustion of wood and coal. They are not counted as greenhouse gases, but also have impact on global warming. Aerosols act directly by absorption and reflection of solar radiation and indirectly by contributing as condensation nuclei for cloud formation and cloud properties change, which in turn affect the climate ( see above). Overall, the human entry of aerosols in recent years has probably acted cooling and so subdued global warming.

Depending on the type aerosols have different effects. Sulfate aerosols affect overall cooling effect. Soot particles, however, absorb thermal radiation and lead to bright surfaces like snow in a lowering of the albedo and thus to a warming and melting polar ice accelerated. Recent studies suggest that more carbon is emitted soot particles and a much larger warming effect than previously thought. The reduction of Rußeintrags is an important and effective climate protection measure to delay the global warming in the short term (atmospheric aerosol concentrations change relatively quickly with changes in emissions, unlike changes in greenhouse gas concentrations that exist long after a reduction in emissions remain ).

The artificial introduction of aerosols into the stratosphere to reflect solar radiation, thereby cooling the earth is sometimes put forward as a proposal to intervene in the course of geoengineering in the air and fight global warming.

Effect of greenhouse gases

The short-wave solar radiation is absorbed at the surface to a large extent, modified heat, and then discharged in the form of thermal radiation. Greenhouse gases can absorb the heat radiation to varying degrees and thus dissipate the heat into the atmosphere due to their chemical nature. The global warming potential of a gas depends crucially on the extent to which its dipole moment can be changed by molecular vibrations. The diatomic gases oxygen and nitrogen do not change their dipole moment by molecular vibrations, and are therefore transparent to infrared radiation. Large molecules, such as, inter alia, Contrast, CFCs have very many vibrational levels and thus many times the global warming potential of CO2, for example.

The effectiveness of a greenhouse gas, so how much can contribute to the release of a gas to the greenhouse effect depends primarily on three factors: the per unit gas release rate ( emission rate ), the spectroscopic properties of the gas, ie how strongly it absorbs the heat radiation in certain wavelength ranges, and its residence time in the atmosphere. The atmospheric dwell time is the time remaining, a substance in the atmosphere, on average, before being removed by chemical or other processes again from it. The longer the residence time of a greenhouse gas, the higher the theoretical effect.

A measure of the greenhouse effect of gas per kilogram of emission quantity is the global warming potential (GWP ) in CO2 equivalents, in which the absorption properties and the residence time are taken into account. The relative global warming potential is normalized to carbon dioxide size at which the effect of a greenhouse gas with an equivalent amount of carbon dioxide is compared. For example, methane has a relative global warming potential of 25, i.e., 1 kg of methane has the same global warming effect as 25 kg of carbon dioxide.

The relative global warming potential is based on a time horizon of 100 years, as a rule, that is, it is the considered over a period of 100 years after the emission averaged warming effect. Relating it to a different time horizon is changing, according to the atmospheric residence time, also the relative global warming potential. Includes a one greenhouse or more chlorine or fluorine atoms, then its relative global warming potential increased due to the high chemical stability significantly compared to greenhouse gases without halogen atom (s).

Satellite-based measurements

Since January 2009, the concentration of the main greenhouse gases is also monitored from space. The satellite Ibuki ( breath) provides current data on the distribution and concentration of carbon dioxide and methane across the globe. The climatology is thereby becoming better data base for the calculation of global warming. Ibuki orbit at 666 km altitude 14 times daily in 100 minutes and returns every three days back to the same places. This can measure the gas concentrations of 56,000 points at a height of up to three kilometers above the earth's surface, the orbiter.

Development of emissions

Germany

According to calculations by the Federal Environment Agency, emissions of greenhouse gases developed favorably in Germany.

• Carbon dioxide: The emissions decreased in 2011 compared to 2010 by 2.4 percent. The cause of the reduced need for heating energy by the milder weather is called, while the higher prices led to lower purchases and use of stocks, so that the power consumption of refineries declined. The lower proportion of nuclear energy led only to slight increase in CO2 emissions. It was exported less power and generates more renewable energy sources. The emissions from energy and industrial facilities of the European emissions trading decreased 2-6 percent. However, cyclical process-related emissions increased.
• Methane: The emissions in 2011 decreased compared to 2010 by 3.5 percent. Here, as the cause of the decline in the landfill of waste (organic ingredients are a major source of methane emission), the decline in subsidized coal quantity and smaller herds called.
• Nitrous oxide: emissions increased by 2.3 percent between 2010 and 2011. This is attributed to the increased sales of nitrogenous fertilizer and konjunkturiell increased chemical production. In addition, the use of catalyst reduced in heavy traffic, the oxides of nitrogen, but increased the emission of nitrous oxide.
• "F- gases ": Here the emissions went down by 0.4 percent. Here, the time effect was offset by the cessation of production of R22 by the rise of refrigerants and sulfur hexafluoride from installed products such as soundproof windows.

Total greenhouse gas emissions fell in Germany in 2011 over the previous year 2010 at 2.9 percent, which corresponds to 27 million tonnes of carbon dioxide equivalents. The emissions could thus be reduced compared to 1990 by almost 27 percent, so that Germany has its climate protection target more than fulfilled. With the Kyoto Protocol, Germany had committed itself by 2012 to reduce its greenhouse gas emissions in the average of the years 2008, 21 percent below the 1990 level.

Worldwide

Global perspective, greenhouse gas emissions are rising more than was even estimated in the worst-case scenarios published in 2007, the last progress report of the IPCC. Alone between 2009 and 2010, the increase in carbon emissions stood at 6%.