Q:-What are the green house gases??
Answers
Answer:
greenhouse gas (sometimes abbreviated GHG) is a gas that absorbs and emits radiant energy within the thermal infrared range. Greenhouse gases cause the greenhouse effect[1] on planets. The primary greenhouse gases in Earth's atmosphere are water vapor (H2O), carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and ozone (O3). Without greenhouse gases, the average temperature of Earth's surface would be about −18 °C (0 °F),[2] rather than the present average of 15 °C (59 °F).[3][4][5] The atmospheres of Venus, Mars and Titan also contain greenhouse gases.
Human activities since the beginning of the Industrial Revolution (around 1750) have produced a 45% increase in the atmospheric concentration of carbon dioxide, from 280 ppm in 1750 to 415 ppm in 2019.[6] This increase has occurred despite the uptake of more than half of the emissions by various natural "sinks" involved in the carbon cycle.[7][8] The vast majority of anthropogenic carbon dioxide emissions come from combustion of fossil fuels, principally coal, oil, and natural gas, with additional contributions coming from deforestation, changes in land use, soil erosion and agriculture (including livestock).[9][10] The leading source of anthropogenic methane emissions is animal agriculture, followed by fugitive emissions from gas, oil, coal and other industry, solid waste, wastewater and rice production.[11]
At current emission rates, temperatures could increase by 2 °C, which the United Nations' Intergovernmental Panel on Climate Change (IPCC) designated as the upper limit to avoid "dangerous" levels, by 2036.[12]
Gases in Earth's atmosphere
The most common gases in Earth's atmosphere are nitrogen (78%), oxygen (21%), and argon (0.9%). The next most common gases are carbon dioxide (0.04%), nitrous oxide, methane, and ozone. They are trace gases that account for almost one tenth of 1% of Earth's atmosphere.
Greenhouse gases are those that absorb and emit infrared radiation in the wavelength range emitted by Earth.[1] In order, the most abundant[clarification needed] greenhouse gases in Earth's atmosphere are:[citation needed]
Water vapor (H
2O)
Carbon dioxide (CO
2)
Methane (CH
4)
Nitrous oxide (N
2O)
Ozone (O
3)
Chlorofluorocarbons (CFCs)
Hydrofluorocarbons (includes HCFCs and HFCs)
Atmospheric concentrations are determined by 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).[13] 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 a given year to that year's total emissions. As of 2006 the annual airborne fraction for CO
2 was about 0.45. The annual airborne fraction increased at a rate of 0.25 ± 0.21% per year over the period 1959–2006.[14]
Non-greenhouse gases
The major atmospheric constituents: nitrogen (N
2), oxygen (O
2), and argon (Ar) are not greenhouse gases because molecules containing two atoms of the same element such as N
2 and O
2 have no net change in the distribution of their electrical charges when they vibrate, and monatomic gases such as Ar do not have vibrational modes. Hence they are almost totally unaffected by infrared radiation. Some molecules containing just two atoms of different elements, such as carbon monoxide (CO) and hydrogen chloride (HCl), do absorb infrared radiation, but these molecules are short-lived in the atmosphere owing to their reactivity and solubility. Therefore, they do not contribute significantly to the greenhouse effect and often are omitted when discussing greenhouse gases.
Some gases have indirect radiative effects (whether or not they are greenhouse gases themselves). This happens in two main ways. One way is that when they break down in the atmosphere they produce another greenhouse gas. For example, methane and carbon monoxide (CO) are oxidized to give carbon dioxide (and methane oxidation also produces water vapor). Oxidation of CO to CO
2 directly produces an unambiguous increase in radiative forcing although the reason is subtle. The peak of the thermal IR emission from Earth's surface is very close to a strong vibrational absorption band of CO
2 (wavelength 15 microns, or wavenumber 667 cm−1). On the other hand, the single CO vibrational band only absorbs IR at much shorter wavelengths (4.7 microns, or 2145 cm−1), where the emission of radiant energy from Earth's surface is at least a factor of ten lower. Oxidation of methane to CO
2, which requires reactions with the OH radical, produces an instantaneous reduction in radiative absorption and emission since CO
2 is a weaker greenhouse gas than methane. However, the oxidations of CO and CH
4 are entwined since both consume OH radicals. In any case, the calculation of the total radiative effect includes both direct and indirect forcing.