Greenhouse gas

These figures rely on national CO2 data that do not include aviation. CO2) remaining in the atmosphere after a specified time.

Such considerations include clouds themselves, air and water vapor density interactions when they are the same or different temperatures, the absorption and release of kinetic energy as water evaporates and condenses to and from vapor, and behaviors related to vapor partial pressure. It is the net concentration changes of the various greenhouse gases by all sources and sinks that determines atmospheric lifetime, not just the removal processes. The global warming potential (GWP) depends on both the efficiency of the molecule as a greenhouse gas and its atmospheric lifetime.

Although molecules containing two atoms of different elements such as carbon monoxide (CO) or hydrogen chloride (HCl) absorb IR, these molecules are short-lived in the atmosphere owing to their reactivity and solubility. According to a preliminary estimate by the Netherlands Environmental Assessment Agency, the largest national producer of CO2 emissions since 2006 has been China with an estimated annual production of about 6200 megatonnes.

For example, on a molecule-for-molecule basis methane is about eight times stronger greenhouse gas than carbon dioxide It is not possible to state that a certain gas causes an exact percentage of the greenhouse effect. During the pre-industrial holocene, concentrations of existing gases were roughly constant.

In the industrial era, human activities have added greenhouse gases to the atmosphere, mainly through the burning of fossil fuels and clearing of forests. The 2007 assessment report compiled by the IPCC noted that changes in atmospheric concentrations of greenhouse gases and aerosols, land cover and solar radiation alter the energy balance of the climate system , and concluded that increases in anthropogenic greenhouse gas concentrations is very likely to have caused most of the increases in global average temperatures since the mid-20th century . Ice cores provide evidence for variation in greenhouse gas concentrations over the past 800,000 years. For example, the release of latent heat by rain in the ITCZ drives atmospheric circulation, clouds vary atmospheric albedo levels, and the oceans provide evaporative cooling that modulates the greenhouse effect down from estimated 67 °C surface temperature. Measurements from Antarctic ice cores show that before industrial emissions started atmospheric CO2 levels were about 280 parts per million by volume (ppmv), and stayed between 260 and 280 during the preceding ten thousand years.

However, this ignores the balancing fluxes of CO2 into the atmosphere from the other reservoirs. Because of the way air is trapped in ice (pores in the ice close off slowly to form bubbles deep within the firn) and the time period represented in each ice sample analyzed, these figures represent averages of atmospheric concentrations of up to a few centuries rather than annual or decadal levels. Since the beginning of the Industrial Revolution, the concentrations of most of the greenhouse gases have increased.

Because water vapor is a greenhouse gas and because warm air can hold more water vapor than cooler air, the primary positive feedback involves water vapor. Thus, if a gas has a high GWP on a short time scale (say 20 years) but has only a short lifetime, it will have a large GWP on a 20 year scale but a small one on a 100 year scale.

This process is the fundamental cause of the greenhouse effect. Human activities since the start of the industrial era around 1750 have increased the levels of greenhouse gases in the atmosphere. In order, Earth s most abundant greenhouse gases are: The contribution to the greenhouse effect by a gas is affected by both the characteristics of the gas and its abundance. This positive feedback does not result in runaway global warming because it is offset by other processes that induce negative feedbacks, which stabilizes average global temperatures.

Carbon monoxide has an atmospheric lifetime of only a few months and as a consequence is spatially more variable than longer-lived gases. Another potentially important indirect effect comes from methane, which in addition to its direct radiative impact also contributes to ozone formation. Before the ice core record, direct data does not exist.

The agency notes that its estimates do not include some CO2 sources of uncertain magnitude. China is followed by the United States with about 5,800 megatonnes.

Greenhouse gases are gases in an atmosphere that absorb and emit radiation within the thermal infrared range. When the warming trend results in effects that induce cooling, the process is referred to as a negative feedback ; this reduces the original warming.

Most widely analysed are those which remove carbon dioxide from the atmosphere, either to geologic formations such as bio-energy with carbon capture and storage Carbon monoxide has an indirect radiative effect by elevating concentrations of methane and tropospheric ozone through scavenging of atmospheric constituents (e.g., the hydroxyl radical, OH) that would otherwise destroy them. However, various proxies and modelling suggests large variations; 500 million years ago CO2 levels were likely 10 times higher than now. Since about 1750 human activity has increased the concentration of carbon dioxide and other greenhouse gases.

Measured atmospheric concentrations of carbon dioxide are currently 100 ppmv higher than pre-industrial levels. It is likely that anthropogenic warming, such as that due to elevated greenhouse gas levels, has had a discernible influence on many physical and biological systems. (2005) Albedo · Bond events · Cloud forcing · Glaciation · Global cooling · Ocean variability (AMO · ENSO · IOD · PDO) · Orbital variations · Orbital forcing · Radiative forcing · Solar variation · Volcanism .

Carbon monoxide is created when carbon-containing fuels are burned incompletely. The atmospheric lifetime of CO2 is often incorrectly stated to be only a few years because that is the average time for any CO2 molecule to stay in the atmosphere before being removed by mixing into the ocean, photosynthesis, or other processes.

Warming is projected to affect various issues such as freshwater resources, industry, food and health. The main sources of greenhouse gases due to human activity are: The seven sources of CO2 from fossil fuel combustion are (with percentage contributions for 2000–2004): The US Environmental Protection Agency (EPA) ranks the major greenhouse gas contributing end-user sectors in the following order: industrial, transportation, residential, commercial and agricultural. Note that ozone depletion has only a minor role in greenhouse warming though the two processes often are confused in the media. Water vapor accounts for the largest percentage of the greenhouse effect, between 36% and 66% for water vapor alone, and between 66% and 85% when factoring in clouds. The Clausius-Clapeyron relation establishes that air can hold more water vapor per unit volume when it warms.

However the per capita emission figures of China are still about one quarter of those of the US population. Relative to 2005, China s fossil CO2 emissions increased in 2006 by 8.7%, while in the USA, comparable CO2 emissions decreased in 2006 by 1.4%. Conversely, if a molecule has a longer atmospheric lifetime than CO2 its GWP will increase with the timescale considered. Examples of the atmospheric lifetime and GWP for several greenhouse gases include: Source: IPCC Fourth Assessment Report, Table 2.14. The use of CFC-12 (except some essential uses) has been phased out due to its ozone depleting properties. Airborne fraction (AF) is the proportion of a emission (e.g.

The average time taken to achieve this is the mean lifetime. This and other basic principles indicate that warming associated with increased concentrations of the other greenhouse gases also will increase the concentration of water vapor. When a warming trend results in effects that induce further warming, the process is referred to as a positive feedback ; this amplifies the original warming.

Through natural processes in the atmosphere, it is eventually oxidized to carbon dioxide. The primary negative feedback is the effect of temperature on emission of infrared radiation: as the temperature of a body increases, the emitted radiation increases with the fourth power of its absolute temperature. Other important considerations involve water vapor being the only greenhouse gas whose concentration is highly variable in space and time in the atmosphere and the only one that also exists in both liquid and solid phases, frequently changing to and from each of the three phases or existing in mixes.

This is because some of the gases absorb and emit radiation at the same frequencies as others, so that the total greenhouse effect is not simply the sum of the influence of each gas. It was recognized in the early 20th century that the greenhouse gases in the atmosphere caused the Earth s overall temperature to be higher than it would be without them. Aside from purely human-produced synthetic halocarbons, most greenhouse gases have both natural and human-caused sources.

Although contributing to many other physical and chemical reactions, the major atmospheric constituents, nitrogen (N2), oxygen (O2), and argon (Ar), are not greenhouse gases. Many observations are available online in a variety of Atmospheric Chemistry Observational Databases. (Source: IPCC radiative forcing report 1994 updated (to 1998) by IPCC TAR table 6.1 ). The sharp acceleration in CO2 emissions since 2000 to more than a 3% increase per year (more than 2 ppm per year) from 1.1% per year during the 1990s is attributable to the lapse of formerly declining trends in carbon intensity of both developing and developed nations.

For example, nitrogen trifluoride has a high global warming potential (GWP) but is only present in very small quantities. Scientists who have elaborated on Arrhenius s theory of global warming are concerned that increasing concentrations of greenhouse gases in the atmosphere are causing an unprecedented rise in global temperatures, with potentially harmful consequences for the environment and human health. GWP is measured relative to the same mass of CO2 and evaluated for a specific timescale.

Some greenhouse gases are not often listed. Major sources of an individual s greenhouse gas include home heating and cooling, electricity consumption, and transportation.

For example, the concentration of carbon dioxide has increased by about 36% to 380 ppmv, or 100 ppmv over modern pre-industrial levels. Canadell (2007) See bio-energy with carbon capture and storage, carbon dioxide air capture, geoengineering and greenhouse gas remediation There exists a number of technologies which produce negative emissions of greenhouse gases.

The higher ends of the ranges quoted are for each gas alone; the lower ends account for overlaps with the other gases. In addition to the main greenhouse gases listed above, other greenhouse gases include sulfur hexafluoride, hydrofluorocarbons and perfluorocarbons (see IPCC list of greenhouse gases). Individual atoms or molecules may be lost or deposited to sinks such as the soil, the oceans and other waters, or vegetation and other biological systems, reducing the excess to background concentrations.

Shindell et al. Both CO2 and CH4 vary between glacial and interglacial phases, and concentrations of these gases correlate strongly with temperature.

Although these tonnages are small compared to the CO2 in the Earth s atmosphere, they are significantly larger than pre-industrial levels. Pounds of Carbon dioxide emitted per million British thermal units of energy for various fuels: Greenhouse gases can be removed from the atmosphere by various processes: Aside from water vapor, which has a residence time of about nine days, major greenhouse gases are well-mixed, and take many years to leave the atmosphere. The atmospheric lifetime of a species therefore measures the time required to restore equilibrium following an increase in its concentration in the atmosphere. This is because molecules containing two atoms of the same element such as N2 and O2 and monatomic molecules such as Ar have no net change in their dipole moment when they vibrate and hence are almost totally unaffected by infrared light.

In the 1960s, the average annual increase was only 37% of what it was in 2000 through 2007. The other greenhouse gases produced from human activity show similar increases in both amount and rate of increase. As a consequence they do not contribute significantly to the greenhouse effect and are not often included when discussing greenhouse gases. Late 19th century scientists experimentally discovered that N2 and O2 did not absorb infrared radiation (called, at that time, dark radiation ) and that water as a vapour and in cloud form, CO2 and many other gases did absorb such radiation.

If one includes indirect emissions, related to the production of electricity, emissions from industry in Europe are roughly stabilized since 1994. Atmospheric levels of CO2 continue to rise, partly a sign of the industrial rise of Asian economies led by China. See also: Asian brown cloud The UK set itself a target of reducing carbon dioxide emissions by 20% from 1990 levels by 2010, but according to its own figures it will fall short of this target by almost 4%. The United States emitted 16.3% more greenhouse gas in 2005 than it did in 1990. Although over 3/4 of cumulative anthropogenic CO2 is still attributable to the developed world, China was responsible for most of global growth in emissions during this period.

Localised plummeting emissions associated with the collapse of the Soviet Union have been followed by slow emissions growth in this region due to more efficient energy use, made necessary by the increasing proportion of it that is exported. The direct emissions from industry have declined due to a constant improvement in energy efficiency, but also to a high penetration of electricity. The first 50 ppmv increase took place in about 200 years, from the start of the Industrial Revolution to around 1973; however the next 50 ppmv increase took place in about 33 years, from 1973 to 2006. Recent data also shows the concentration is increasing at a higher rate.

Corresponding conservation measures are improving home building insulation, installing geothermal heat pumps and compact fluorescent lamps, and choosing energy-efficient vehicles. Carbon dioxide, methane, nitrous oxide and three groups of fluorinated gases (sulfur hexafluoride, HFCs, and PFCs) are the major greenhouse gases and the subject of the Kyoto Protocol, which came into force in 2005. Although CFCs are greenhouse gases, they are regulated by the Montreal Protocol, which was motivated by CFCs contribution to ozone depletion rather than by their contribution to global warming.