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82-604: The Chicago Climate Exchange (CCX) was a voluntary, legally binding greenhouse gas reduction and trading system for emission sources and offset projects in North America and Brazil. CCX employed independent verification, included six greenhouse gases, and traded greenhouse gas emission allowances from 2003 to 2010. The companies joining the exchange committed to reducing their aggregate emissions by 6% by 2010. CCX had an aggregate baseline of 680 million metric tons of CO 2 equivalent . CCX ceased trading carbon credits at
164-560: A carbon credit (termed a CFI or Carbon Financial Instrument) was reached in November 2010 when the carbon credit price per metric ton of CO 2 was between 5 and 10 US cents, down from its highest value of 750 US cents in May 2008. Trading reached zero monthly volume in February 2010 and remained at zero for the next nine months when the decision to close the exchange was announced. The trading system had
246-411: A given year to that year's total emissions. The annual airborne fraction for CO 2 had been stable at 0.45 for the past six decades even as the emissions have been increasing. This means that the other 0.55 of emitted CO 2 is absorbed by the land and atmosphere carbon sinks within the first year of an emission. In the high-emission scenarios, the effectiveness of carbon sinks will be lower, increasing
328-400: A greenhouse gas would absorb over a given time frame after it has been added to the atmosphere (or emitted to the atmosphere). The GWP makes different greenhouse gases comparable with regard to their "effectiveness in causing radiative forcing ". It is expressed as a multiple of the radiation that would be absorbed by the same mass of added carbon dioxide (CO 2 ), which is taken as
410-473: A high rate of thermal radiation being emitted to space. This is because the atmosphere is generally much colder than the surface, and the rate at which longwave radiation is emitted scales as the fourth power of temperature. Thus, the higher the altitude at which longwave radiation is emitted, the lower its intensity. The atmosphere is relatively transparent to solar radiation, but it is nearly opaque to longwave radiation. The atmosphere typically absorbs most of
492-520: A higher rate than it leaves, corresponding to planetary warming. The energy imbalance has been increasing. It can take decades to centuries for oceans to warm and planetary temperature to shift sufficiently to compensate for an energy imbalance. Thermal radiation is emitted by nearly all matter, in proportion to the fourth power of its absolute temperature. In particular, the emitted energy flux, M {\displaystyle M} (measured in W/m )
574-424: A lower flux of long-wave radiation penetrating to higher altitudes. Clouds are effective at absorbing and scattering longwave radiation, and therefore reduce the amount of outgoing longwave radiation. Clouds have both cooling and warming effects. They have a cooling effect insofar as they reflect sunlight (as measured by cloud albedo ), and a warming effect, insofar as they absorb longwave radiation. For low clouds,
656-539: A molecule of X remains in the box. τ {\displaystyle \tau } can also be defined as the ratio of the mass m {\displaystyle m} (in kg) of X in the box to its removal rate, which is the sum of the flow of X out of the box ( F out {\displaystyle F_{\text{out}}} ), chemical loss of X ( L {\displaystyle L} ), and deposition of X ( D {\displaystyle D} ) (all in kg/s): If input of this gas into
738-414: A much shorter atmospheric lifetime than carbon dioxide, its GWP is much less over longer time periods, with a GWP-100 of 27.9 and a GWP-500 of 7.95. The contribution of each gas to the enhanced greenhouse effect is determined by the characteristics of that gas, its abundance, and any indirect effects it may cause. For example, the direct radiative effect of a mass of methane is about 84 times stronger than
820-421: A negligible ability to absorb or emit longwave thermal radiation. Consequently, the ability of air to absorb and emit longwave radiation is determined by the concentration of trace gases like water vapor and carbon dioxide. According to Kirchhoff's law of thermal radiation , the emissivity of matter is always equal to its absorptivity, at a given wavelength. At some wavelengths, greenhouse gases absorb 100% of
902-445: A process known as water vapor feedback. It occurs because Clausius–Clapeyron relation establishes that more water vapor will be present per unit volume at elevated temperatures. Thus, local atmospheric concentration of water vapor varies from less than 0.01% in extremely cold regions and up to 3% by mass in saturated air at about 32 °C. Global warming potential (GWP) is an index to measure how much infrared thermal radiation
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#1732851159514984-500: A reference gas. Therefore, the GWP has a value of 1 for CO 2 . For other gases it depends on how strongly the gas absorbs infrared thermal radiation, how quickly the gas leaves the atmosphere, and the time frame being considered. For example, methane has a GWP over 20 years (GWP-20) of 81.2 meaning that, for example, a leak of a tonne of methane is equivalent to emitting 81.2 tonnes of carbon dioxide measured over 20 years. As methane has
1066-408: A single number. Scientists instead say that while the first 10% of carbon dioxide's airborne fraction (not counting the ~50% absorbed by land and ocean sinks within the emission's first year) is removed "quickly", the vast majority of the airborne fraction – 80% – lasts for "centuries to millennia". The remaining 10% stays for tens of thousands of years. In some models, this longest-lasting fraction
1148-451: A smaller energy imbalance (EEI). Similarly, if energy arrives at a lower rate than it leaves (i.e., ASR < OLR, so than EEI is negative), the amount of energy in Earth's climate decreases, and temperatures tend to decrease overall. As temperatures decrease, OLR decreases, making the imbalance closer to zero. In this fashion, a planet naturally constantly adjusts its temperature so as to keep
1230-405: A system but does not leave must be retained within the system. So, the amount of energy retained on Earth (in Earth's climate system) is governed by an equation: Energy arrives in the form of absorbed solar radiation (ASR). Energy leaves as outgoing longwave radiation (OLR). Thus, the rate of change in the energy in Earth's climate system is given by Earth's energy imbalance (EEI): When energy
1312-481: A variety of Atmospheric Chemistry Observational Databases . The table below shows the most influential long-lived, well-mixed greenhouse gases, along with their tropospheric concentrations and direct radiative forcings , as identified by the Intergovernmental Panel on Climate Change (IPCC). Abundances of these trace gases are regularly measured by atmospheric scientists from samples collected throughout
1394-508: Is a CO 2 molecule. The first 30 ppm increase in CO 2 concentrations took place in about 200 years, from the start of the Industrial Revolution to 1958; however the next 90 ppm increase took place within 56 years, from 1958 to 2014. Similarly, the average annual increase in the 1960s was only 37% of what it was in 2000 through 2007. Many observations are available online in
1476-483: Is a level which the Intergovernmental Panel on Climate Change (IPCC) says is "dangerous". Greenhouse gases are infrared active, meaning that they absorb and emit infrared radiation in the same long wavelength range as what is emitted by the Earth's surface, clouds and atmosphere. 99% of the Earth's dry atmosphere (excluding water vapor ) is made up of nitrogen ( N 2 ) (78%) and oxygen ( O 2 ) (21%). Because their molecules contain two atoms of
1558-434: Is also cooling the upper atmosphere, as it is much thinner than the lower layers, and any heat re-emitted from greenhouse gases is more likely to travel further to space than to interact with the fewer gas molecules in the upper layers. The upper atmosphere is also shrinking as the result. Anthropogenic changes to the natural greenhouse effect are sometimes referred to as the enhanced greenhouse effect . This table shows
1640-561: Is also referred to as terrestrial radiation . This radiation is in the infrared portion of the spectrum, but is distinct from the shortwave (SW) near-infrared radiation found in sunlight. Outgoing longwave radiation ( OLR ) is the longwave radiation emitted to space from the top of Earth's atmosphere. It may also be referred to as emitted terrestrial radiation . Outgoing longwave radiation plays an important role in planetary cooling. Longwave radiation generally spans wavelengths ranging from 3–100 micrometres (μm). A cutoff of 4 μm
1722-489: Is an asymmetry in electric charge distribution which allows molecular vibrations to interact with electromagnetic radiation. This makes them infrared active, and so their presence causes greenhouse effect . Earth absorbs some of the radiant energy received from the sun, reflects some of it as light and reflects or radiates the rest back to space as heat . A planet's surface temperature depends on this balance between incoming and outgoing energy. When Earth's energy balance
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#17328511595141804-508: Is arriving at a higher rate than it leaves (i.e., ASR > OLR, so that EEI is positive), the amount of energy in Earth's climate increases. Temperature is a measure of the amount of thermal energy in matter. So, under these circumstances, temperatures tend to increase overall (though temperatures might decrease in some places as the distribution of energy changes). As temperatures increase, the amount of thermal radiation emitted also increases, leading to more outgoing longwave radiation (OLR), and
1886-503: Is as large as 30%. Estimates in 2023 found that the current carbon dioxide concentration in the atmosphere may be the highest it has been in the last 14 million years. However the IPCC Sixth Assessment Report estimated similar levels 3 to 3.3 million years ago in the mid-Pliocene warm period . This period can be a proxy for likely climate outcomes with current levels of CO 2 . Greenhouse gas monitoring involves
1968-428: Is dominated by longwave radiation during the night and in the polar regions. While there is no absorbed solar radiation during the night, terrestrial radiation continues to be emitted, primarily as a result of solar energy absorbed during the day. The reduction of the outgoing longwave radiation (OLR), relative to longwave radiation emitted by the surface, is at the heart of the greenhouse effect . More specifically,
2050-447: Is emitted compared to what a perfect blackbody would emit. The emissivity of Earth's surface has been measured to be in the range 0.65 to 0.99 (based on observations in the 8-13 micron wavelength range) with the lowest values being for barren desert regions. The emissivity is mostly above 0.9, and the global average surface emissivity is estimated to be around 0.95. The most common gases in air (i.e., nitrogen, oxygen, and argon) have
2132-480: Is given by the Stefan–Boltzmann law for non- blackbody matter: where T {\displaystyle T} is the absolute temperature , σ {\displaystyle \sigma } is the Stefan–Boltzmann constant , and ϵ {\displaystyle \epsilon } is the emissivity . The emissivity is a value between zero and one which indicates how much less radiation
2214-503: Is in the stratosphere), increased greenhouse gas concentration can still lead to significant reductions in OLR at other wavelengths where absorption is weaker. When OLR decreases, this leads to an energy imbalance, with energy received being greater than energy lost, causing a warming effect. Therefore, an increase in the concentrations of greenhouse gases causes energy to accumulate in Earth's climate system, contributing to global warming . If
2296-403: Is mostly due to the rapid growth and cumulative magnitude of the disturbances to Earth's carbon cycle by the geologic extraction and burning of fossil carbon. As of year 2014, fossil CO 2 emitted as a theoretical 10 to 100 GtC pulse on top of the existing atmospheric concentration was expected to be 50% removed by land vegetation and ocean sinks in less than about a century, as based on
2378-415: Is obtained by dividing the total energy flow over the surface of the globe (measured in watts) by the surface area of the Earth, 5.1 × 10 m (5.1 × 10 km ; 2.0 × 10 sq mi). Emitting outgoing longwave radiation is the only way Earth loses energy to space, i.e., the only way the planet cools itself. Radiative heating from absorbed sunlight, and radiative cooling to space via OLR power
2460-507: Is shifted, its surface becomes warmer or cooler, leading to a variety of changes in global climate. Radiative forcing is a metric calculated in watts per square meter, which characterizes the impact of an external change in a factor that influences climate. It is calculated as the difference in top-of-atmosphere (TOA) energy balance immediately caused by such an external change. A positive forcing, such as from increased concentrations of greenhouse gases, means more energy arriving than leaving at
2542-407: Is sometimes used to differentiate sunlight from longwave radiation. Less than 1% of sunlight has wavelengths greater than 4 μm. Over 99% of outgoing longwave radiation has wavelengths between 4 μm and 100 μm. The flux of energy transported by outgoing longwave radiation is typically measured in units of watts per metre squared (W⋅m ). In the case of global energy flux, the W/m value
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2624-482: Is the level the United Nations' Intergovernmental Panel on Climate Change (IPCC) says is "dangerous". Most greenhouse gases have both natural and human-caused sources. An exception are purely human-produced synthetic halocarbons which have no natural sources. During the pre-industrial Holocene , concentrations of existing gases were roughly constant, because the large natural sources and sinks roughly balanced. In
2706-499: Is the most important greenhouse gas overall, being responsible for 41–67% of the greenhouse effect, but its global concentrations are not directly affected by human activity. While local water vapor concentrations can be affected by developments such as irrigation , it has little impact on the global scale due to its short residence time of about nine days. Indirectly, an increase in global temperatures cause will also increase water vapor concentrations and thus their warming effect, in
2788-712: Is warmed by sunlight, causing its surface to radiate heat , which is then mostly absorbed by greenhouse gases. Without greenhouse gases in the atmosphere, the average temperature of Earth's surface would be about −18 °C (0 °F), rather than the present average of 15 °C (59 °F). The five most abundant greenhouse gases in Earth's atmosphere, listed in decreasing order of average global mole fraction , are: water vapor , carbon dioxide , methane , nitrous oxide , ozone . Other greenhouse gases of concern include chlorofluorocarbons (CFCs and HCFCs ), hydrofluorocarbons (HFCs), perfluorocarbons , SF 6 , and NF 3 . Water vapor causes about half of
2870-465: The Iowa Farm Bureau to the government-run passenger rail corporation, Amtrak . Greenhouse gas Greenhouse gases ( GHGs ) are the gases in the atmosphere that raise the surface temperature of planets such as the Earth. What distinguishes them from other gases is that they absorb the wavelengths of radiation that a planet emits , resulting in the greenhouse effect . The Earth
2952-526: The greenhouse effect is heavily driven by water vapor , human emissions of water vapor are not a significant contributor to warming. The annual "Emissions Gap Report" by UNEP stated in 2022 that it was necessary to almost halve emissions. "To get on track for limiting global warming to 1.5°C, global annual GHG emissions must be reduced by 45 per cent compared with emissions projections under policies currently in place in just eight years, and they must continue to decline rapidly after 2030, to avoid exhausting
3034-472: The heat engine that drives atmospheric dynamics . The balance between OLR (energy lost) and incoming solar shortwave radiation (energy gained) determines whether the Earth is experiencing global heating or cooling (see Earth's energy budget ). Outgoing longwave radiation (OLR) constitutes a critical component of Earth's energy budget . The principle of conservation of energy says that energy cannot appear or disappear. Thus, any energy that enters
3116-508: The U.S. carbon markets. The market value of the carbon credits had crashed, it was said, because legislation to mandate participation could not pass due to Republican opposition, while others pointed to "a flood of credits from offset project generators." In November 2010, the Climate Exchange stated that it would cease trading carbon credits at the end of 2010, although carbon exchanges will still be facilitated. The effective final value of
3198-422: The absorptivity of the gas is high and the gas is present in a high enough concentration, the absorption at certain wavelengths becomes saturated. This means there is enough gas present to completely absorb the radiated energy at that wavelength before the upper atmosphere is reached. It is sometimes incorrectly argued that this means an increase in the concentration of this gas will have no additional effect on
3280-424: The atmosphere does not absorb longwave radiation (except for the ozone band between 9.6 and 9.8 μm). Greenhouse gases in the atmosphere are responsible for a majority of the absorption of longwave radiation in the atmosphere. The most important of these gases are water vapor , carbon dioxide , methane , and ozone . The absorption of longwave radiation by gases depends on the specific absorption bands of
3362-469: The atmosphere into bodies of water (ocean, lakes, etc.), as well as dissolving in precipitation as raindrops fall through the atmosphere. When dissolved in water, carbon dioxide reacts with water molecules and forms carbonic acid , which contributes to ocean acidity . It can then be absorbed by rocks through weathering . It also can acidify other surfaces it touches or be washed into the ocean. The vast majority of carbon dioxide emissions by humans come from
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3444-440: The atmosphere result in greater absorption because of the cumulative absorption by many layers of gas. Lastly, the temperature and altitude of the absorbing gas also affect its absorption of longwave radiation. OLR is affected by Earth's surface skin temperature (i.e, the temperature of the top layer of the surface), skin surface emissivity, atmospheric temperature, water vapor profile, and cloud cover. The net all-wave radiation
3526-427: The atmosphere, terrestrial ecosystems , the ocean, and sediments . These flows have been fairly balanced over the past 1 million years, although greenhouse gas levels have varied widely in the more distant past . Carbon dioxide levels are now higher than they have been for 3 million years. If current emission rates continue then global warming will surpass 2.0 °C (3.6 °F) sometime between 2040 and 2070. This
3608-459: The atmospheric fraction of CO 2 even though the raw amount of emissions absorbed will be higher than in the present. Major greenhouse gases are well mixed and take many years to leave the atmosphere. The atmospheric lifetime of a greenhouse gas refers to the time required to restore equilibrium following a sudden increase or decrease in its concentration in the atmosphere. Individual atoms or molecules may be lost or deposited to sinks such as
3690-423: The balance between sources (emissions of the gas from human activities and natural systems) and sinks (the removal of the gas from the atmosphere by conversion to a different chemical compound or absorption by bodies of water). The proportion of an emission remaining in the atmosphere after a specified time is the " airborne fraction " (AF). The annual airborne fraction is the ratio of the atmospheric increase in
3772-502: The box ceased, then after time τ {\displaystyle \tau } , its concentration would decrease by about 63%. Changes to any of these variables can alter the atmospheric lifetime of a greenhouse gas. For instance, methane's atmospheric lifetime is estimated to have been lower in the 19th century than now, but to have been higher in the second half of the 20th century than after 2000. Carbon dioxide has an even more variable lifetime, which cannot be specified down to
3854-401: The burning of fossil fuels , with remaining contributions from agriculture and industry . Methane emissions originate from agriculture, fossil fuel production, waste, and other sources. The carbon cycle takes thousands of years to fully absorb CO 2 from the atmosphere, while methane lasts in the atmosphere for an average of only 12 years. Natural flows of carbon happen between
3936-405: The burning of fossil fuels . Additional contributions come from cement manufacturing, fertilizer production, and changes in land use like deforestation . Methane emissions originate from agriculture , fossil fuel production, waste, and other sources. If current emission rates continue then temperature rises will surpass 2.0 °C (3.6 °F) sometime between 2040 and 2070, which
4018-615: The commencement of trading in the European Union through the ETS system . The Valley Wood Carbon Sequestration Project, the first such project to be verified through the Chicago Climate Exchange, was the recipient of offset funding generated through a unique partnership, developed in 2008 by Verus Carbon Neutral, that brought together 17 merchants of Atlanta's Virginia-Highland shopping and dining neighborhood retail district to establish
4100-416: The concentration of a greenhouse gas (such as carbon dioxide (CO 2 ), methane (CH 4 ), nitrous oxide (N 2 O), and water vapor (H 2 O) and is increased, this has a number of effects. At a given wavelength The size of the reduction in OLR will vary by wavelength. Even if OLR does not decrease at certain wavelengths (e.g., because 100% of surface emissions are absorbed and the emission altitude
4182-399: The development of clouds. Observing this radiative flux from a surface also provides a practical way of assessing surface temperatures on both local and global scales. This energy distribution is what drives atmospheric thermodynamics . Outgoing long-wave radiation (OLR) has been monitored and reported since 1970 by a progression of satellite missions and instruments. Longwave radiation at
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#17328511595144264-454: The direct measurement of atmospheric concentrations and direct and indirect measurement of greenhouse gas emissions . Indirect methods calculate emissions of greenhouse gases based on related metrics such as fossil fuel extraction. There are several different methods of measuring carbon dioxide concentrations in the atmosphere, including infrared analyzing and manometry . Methane and nitrous oxide are measured by other instruments, such as
4346-764: The end of 2010 due to inactivity in the U.S. carbon markets, although carbon exchanges were intended to still be facilitated. Until 2010 CCX was operated by the public company Climate Exchange PLC, which also owned the European Climate Exchange . Richard Sandor , creator of the Sustainable Performance Group, founded the exchange and has been a spokesman for it. The exchange traded in emissions of six gases: carbon dioxide , methane , nitrous oxide , sulfur hexafluoride , perfluorocarbons and hydrofluorocarbons . CCX started trading in October 2003, prior to
4428-506: The energy imbalance small. If there is more solar radiation absorbed than OLR emitted, the planet will heat up. If there is more OLR than absorbed solar radiation the planet will cool. In both cases, the temperature change works to shift the energy imbalance towards zero. When the energy imbalance is zero, a planet is said to be in radiative equilibrium . Planets natural tend to a state of approximate radiative equilibrium. In recent decades, energy has been measured to be arriving on Earth at
4510-590: The first Carbon Neutral Zone in the United States. IntercontinentalExchange ( NYSE : ICE ), a leading operator of regulated global futures exchanges, clearing houses and over-the-counter (OTC) markets, agreed to acquire Climate Exchange plc in January 2009, the acquisition was completed in July 2010 and was followed by an announcement that half of the company's Chicago-based workforce would be laid off due to inactivity in
4592-484: The following three parts. The exchange had more than 400 members ranging from corporations like Ford , DuPont , and Motorola , to state and municipalities such as Oakland and Chicago, to educational institutions such as University of California, San Diego, Tufts University , Michigan State University and University of Minnesota , to farmers and their organizations, such as the National Farmers Union and
4674-427: The gases in the atmosphere. The specific absorption bands are determined by their molecular structure and energy levels. Each type of greenhouse gas has a unique group of absorption bands that correspond to particular wavelengths of radiation that the gas can absorb. The OLR balance is affected by clouds, dust, and aerosols in the atmosphere. Clouds tend to block penetration of upwelling longwave radiation, causing
4756-403: The greenhouse effect may be defined quantitatively as the amount of longwave radiation emitted by the surface that does not reach space. On Earth as of 2015, about 398 W/m of longwave radiation was emitted by the surface, while OLR, the amount reaching space, was 239 W/m . Thus, the greenhouse effect was 398−239 = 159 W/m , or 159/398 = 40% of surface emissions, not reaching space. When
4838-446: The greenhouse effect, acting in response to other gases as a climate change feedback . Human activities since the beginning of the Industrial Revolution (around 1750) have increased carbon dioxide by over 50% , and methane levels by 150%. Carbon dioxide emissions are causing about three-quarters of global warming , while methane emissions cause most of the rest. The vast majority of carbon dioxide emissions by humans come from
4920-461: The increased concentration leads to the atmosphere emitting longwave radiation to space from a higher altitude. If the air at that higher altitude is colder (as is true throughout the troposphere), then thermal emissions to space will be reduced, decreasing OLR. False conclusions about the implications of absorption being "saturated" are examples of the surface budget fallacy , i.e., erroneous reasoning that results from focusing on energy exchange at
5002-506: The industrial era, human activities have added greenhouse gases to the atmosphere, mainly through the burning of fossil fuels and clearing of forests. The major anthropogenic (human origin) sources of greenhouse gases are carbon dioxide (CO 2 ), nitrous oxide ( N 2 O ), methane and three groups of fluorinated gases ( sulfur hexafluoride ( SF 6 ), hydrofluorocarbons (HFCs) and perfluorocarbons (PFCs, sulphur hexafluoride (SF 6 ), and nitrogen trifluoride (NF 3 )). Though
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#17328511595145084-455: The limited remaining atmospheric carbon budget ." The report commented that the world should focus on broad-based economy-wide transformations and not incremental change. Several technologies remove greenhouse gas emissions from the atmosphere. Most widely analyzed are those that remove carbon dioxide from the atmosphere, either to geologic formations such as bio-energy with carbon capture and storage and carbon dioxide air capture , or to
5166-415: The longwave radiation emitted by the surface. Absorption of longwave radiation prevents that radiation from reaching space. At wavelengths where the atmosphere absorbs surface radiation, some portion of the radiation that was absorbed is replaced by a lesser amount of thermal radiation emitted by the atmosphere at a higher altitude. When absorbed, the energy transmitted by this radiation is transferred to
5248-407: The longwave radiation emitted by the surface. So, at those wavelengths, the emissivity of the atmosphere is 1 and the atmosphere emits thermal radiation much like an ideal blackbody would. However, this applies only at wavelengths where the atmosphere fully absorbs longwave radiation. Although greenhouse gases in air have a high emissivity at some wavelengths, this does not necessarily correspond to
5330-828: The most important contributions to the overall greenhouse effect, without which the average temperature of Earth's surface would be about −18 °C (0 °F), instead of around 15 °C (59 °F). This table also specifies tropospheric ozone , because this gas has a cooling effect in the stratosphere , but a warming influence comparable to nitrous oxide and CFCs in the troposphere . K&T (1997) used 353 ppm CO 2 and calculated 125 W/m total clear-sky greenhouse effect; relied on single atmospheric profile and cloud model. "With Clouds" percentages are from Schmidt (2010) interpretation of K&T (1997). Schmidt (2010) used 1980 climatology with 339 ppm CO 2 and 155 W/m total greenhouse effect; accounted for temporal and 3-D spatial distribution of absorbers. Water vapor
5412-431: The planet's energy budget. This argument neglects the fact that outgoing longwave radiation is determined not only by the amount of surface radiation that is absorbed , but also by the altitude (and temperature) at which longwave radiation is emitted to space. Even if 100% of surface emissions are absorbed at a given wavelength, the OLR at that wavelength can still be reduced by increased greenhouse gas concentration, since
5494-505: The projections of coupled models referenced in the AR5 assessment. A substantial fraction (20–35%) was also projected to remain in the atmosphere for centuries to millennia, where fractional persistence increases with pulse size. Values are relative to year 1750. AR6 reports the effective radiative forcing which includes effects of rapid adjustments in the atmosphere and at the surface. Atmospheric concentrations are determined by
5576-763: The range-resolved infrared differential absorption lidar (DIAL). Greenhouse gases are measured from space such as by the Orbiting Carbon Observatory and through networks of ground stations such as the Integrated Carbon Observation System . The Annual Greenhouse Gas Index (AGGI) is defined by atmospheric scientists at NOAA as the ratio of total direct radiative forcing due to long-lived and well-mixed greenhouse gases for any year for which adequate global measurements exist, to that present in year 1990. These radiative forcing levels are relative to those present in year 1750 (i.e. prior to
5658-472: The reflection of solar radiation is the larger effect; so, these clouds cool the Earth. In contrast, for high thin clouds in cold air, the absorption of longwave radiation is the more significant effect; so these clouds warm the planet. The interaction between emitted longwave radiation and the atmosphere is complicated due to the factors that affect absorption. The path of the radiation in the atmosphere also determines radiative absorption: longer paths through
5740-605: The same element , they have no asymmetry in the distribution of their electrical charges , and so are almost totally unaffected by infrared thermal radiation, with only an extremely minor effect from collision-induced absorption . A further 0.9% of the atmosphere is made up by argon (Ar), which is monatomic , and so completely transparent to thermal radiation. On the other hand, carbon dioxide (0.04%), methane , nitrous oxide and even less abundant trace gases account for less than 0.1% of Earth's atmosphere, but because their molecules contain atoms of different elements, there
5822-470: The same mass of carbon dioxide over a 20-year time frame. Since the 1980s, greenhouse gas forcing contributions (relative to year 1750) are also estimated with high accuracy using IPCC-recommended expressions derived from radiative transfer models . The concentration of a greenhouse gas is typically measured in parts per million (ppm) or parts per billion (ppb) by volume. A CO 2 concentration of 420 ppm means that 420 out of every million air molecules
5904-469: The soil as in the case with biochar . Many long-term climate scenario models require large-scale human-made negative emissions to avoid serious climate change. Negative emissions approaches are also being studied for atmospheric methane, called atmospheric methane removal . Outgoing longwave radiation In climate science , longwave radiation ( LWR ) is electromagnetic thermal radiation emitted by Earth's surface, atmosphere, and clouds. It
5986-404: The soil, the oceans and other waters, or vegetation and other biological systems, reducing the excess to background concentrations. The average time taken to achieve this is the mean lifetime . This can be represented through the following formula, where the lifetime τ {\displaystyle \tau } of an atmospheric species X in a one- box model is the average time that
6068-510: The start of the industrial era ). 1990 is chosen because it is the baseline year for the Kyoto Protocol , and is the publication year of the first IPCC Scientific Assessment of Climate Change . As such, NOAA states that the AGGI "measures the commitment that (global) society has already made to living in a changing climate. It is based on the highest quality atmospheric observations from sites around
6150-431: The substance that absorbed it. However, overall, greenhouse gases in the troposphere emit more thermal radiation than they absorb, so longwave radiative heat transfer has a net cooling effect on air. Assuming no cloud cover, most of the surface emissions that reach space do so through the atmospheric window . The atmospheric window is a region of the electromagnetic wavelength spectrum between 8 and 11 μm where
6232-804: The surface (both outward and inward) is mainly measured by pyrgeometers . A most notable ground-based network for monitoring surface long-wave radiation is the Baseline Surface Radiation Network (BSRN) , which provides crucial well-calibrated measurements for studying global dimming and brightening. Data on surface longwave radiation and OLR is available from a number of sources including: Many applications call for calculation of long-wave radiation quantities. Local radiative cooling by outgoing longwave radiation, suppression of radiative cooling (by downwelling longwave radiation cancelling out energy transfer by upwelling longwave radiation), and radiative heating through incoming solar radiation drive
6314-400: The surface, instead of focusing on the top-of-atmosphere (TOA) energy balance. Measurements of outgoing longwave radiation at the top of the atmosphere and of longwave radiation back towards the surface are important to understand how much energy is retained in Earth's climate system: for example, how thermal radiation cools and warms the surface, and how this energy is distributed to affect
6396-418: The table. and Annex III of the 2021 IPCC WG1 Report (years) GWP over time up to year 2022 Year 1750 Year 1998 Year 2005 Year 2011 Year 2019 Mole fractions : μmol/mol = ppm = parts per million (10 ); nmol/mol = ppb = parts per billion (10 ); pmol/mol = ppt = parts per trillion (10 ). The IPCC states that "no single atmospheric lifetime can be given" for CO 2 . This
6478-446: The temperature and dynamics of different parts of the atmosphere. By using the radiance measured from a particular direction by an instrument, atmospheric properties (like temperature or humidity ) can be inversely inferred . Calculations of these quantities solve the radiative transfer equations that describe radiation in the atmosphere. Usually the solution is done numerically by atmospheric radiative transfer codes adapted to
6560-424: The top-of-atmosphere, which causes additional warming, while negative forcing, like from sulfates forming in the atmosphere from sulfur dioxide , leads to cooling. Within the lower atmosphere, greenhouse gases exchange thermal radiation with the surface and limit radiative heat flow away from it, which reduces the overall rate of upward radiative heat transfer. The increased concentration of greenhouse gases
6642-602: The world. It excludes water vapor because changes in its concentrations are calculated as a climate change feedback indirectly caused by changes in other greenhouse gases, as well as ozone, whose concentrations are only modified indirectly by various refrigerants that cause ozone depletion . Some short-lived gases (e.g. carbon monoxide , NOx ) and aerosols (e.g. mineral dust or black carbon ) are also excluded because of limited role and strong variation, along with minor refrigerants and other halogenated gases, which have been mass-produced in smaller quantities than those in
6724-408: The world. Its uncertainty is very low." The natural flows of carbon between the atmosphere, ocean, terrestrial ecosystems , and sediments are fairly balanced; so carbon levels would be roughly stable without human influence. Carbon dioxide is removed from the atmosphere primarily through photosynthesis and enters the terrestrial and oceanic biospheres. Carbon dioxide also dissolves directly from
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