Causes Of Greenhouse Effect And Global Warming Pdf
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Global Warming - Causes, Impacts and Remedies.
Global Warming 101
Global Warming - Causes, Impacts and Remedies. Radiative forcing values are estimated by a numerical process using radiative transfer schemes for terrestrial radiation and data from general circulation models. However, the estimation is complex and difficult to understand for non-specialists, including researchers in other fields.
Understanding the essence of the Earth system is important for correctly discussing global environmental issues. Accordingly, in this chapter, radiative forcing values are calculated from a simple, intuitive radiative transfer model using the absorption spectra of greenhouse gases and the Planck formula for terrestrial radiation.
The global atmospheric carbon dioxide CO 2 concentration has increased from about ppmv in pre-industrial times defined as to During the same period, the concentrations of methane CH 4 and nitrous oxide N 2 O have also increased from about 0. Concentrations in and , radiative forcing, and global warming potential for each greenhouse gas. However, increasing the concentration of greenhouse gases decreases the energy flux to outer space and changes the energy flux to the Earth into a surplus.
Radiative forcing is defined as the imbalance of the energy flux density caused by these perturbations. The Intergovernmental Panel on Climate Change IPCC has estimated the following radiative forcing values due to increased greenhouse gas concentrations in relative to their pre-industrial levels: CO 2 , 1.
The unit of radiative forcing is the same as that of energy flux density. While the magnitude of the positive radiative forcing of greenhouse gases is well understood, the effects of other atmospheric constituents such as aerosols are subject to considerable uncertainty. Radiative forcing to be compared with calculated value in this chapter is the direct contribution: CO 2 , 1. Global warming potential GWP is also used in comprehensive policies regarding the regulation of greenhouse gases.
GWP is a measure of how much a given mass of a greenhouse gas contributes to global warming and is usually defined as the radiative forcing resulting from an instantaneous release of 1 kg of the greenhouse gas into the atmosphere relative to that of CO 2. Radiative forcing is estimated by a numerical process using radiative transfer schemes for terrestrial radiation and data from models referred to as general circulation models.
Yet, understanding the essence of the Earth system is important for correctly discussing global environmental issues. It is therefore necessary to create models such that anyone who has acquired basic scientific knowledge can intuitively understand the Earth system as well as the essence of the calculations based on the models.
In this chapter, radiative forcing values are calculated from a simple radiative transfer model using the absorption spectra of greenhouse gases and the Planck formula for terrestrial radiation. Furthermore, the GWPs of specific greenhouse gases are derived. The mean vertical temperature of the atmosphere results from the balance between heating and cooling. At the surface, solar heating is balanced by convective transport of latent and sensible heat to the troposphere. In the troposphere, radiative cooling infrared emission by molecules is balanced by the release of latent heat via condensation and precipitation and by convective transport of sensible heat from the surface.
This radiative-convective interaction leads to a roughly constant lapse rate in the troposphere. Vertical concentration profiles of four principal greenhouse gases. Concentrations are shown in units of ppmv. The IPCC has defined radiative forcing as the change in net energy flux density at the tropopause.
Figure 1 shows the altitude dependence of the concentrations of the four principal greenhouse gases. Water vapor is the most abundant and important greenhouse gas in the atmosphere. Nevertheless, it is excluded as an objective of the radiative forcing estimation since humans cannot directly control it. However, because of its strong absorption band, water vapor should be considered when calculating the radiative forcing of the other greenhouse gases.
The first step in building the model is to divide the atmosphere into appropriate layers, where the pressure, temperature, and concentration of each greenhouse gas are homogeneous within each layer. Moreover, the temperature of the troposphere decreases with altitude at a roughly constant lapse rate. Therefore, up to an altitude of 11 km, the atmosphere is divided into layers, each with a thickness of m. The bottom layer tangent to the surface is referred to as the zeroth layer for descriptive purposes.
Some of the incident flux is absorbed by the molecules of greenhouse gases in the layer, and the remainder is transmitted. Subsequently, the molecules emit radiation flux both upward and downward.
Some of the combined upward flux transmitted flux and emitted upward flux is again absorbed in the first layer, and the layer emits radiation. The repetition of this simple radiative transfer process leads to the outgoing flux from the tropopause to outer space. In the next step, the flux density F i is similarly calculated for an atmosphere in which the concentration of a specific greenhouse gas i increases up to its level in , keeping everything else constant including the temperature.
In these processes, the effects of the near-infrared region of incident solar radiation are ignored. Also, the intensities of absorption and emission depend on only the respective number densities of the greenhouse gases in the layer.
Pressure and temperature affect these intensities through only a change in number density. Thus, for the same concentration of a given greenhouse gas, the ratio of the absorption or emission of an arbitrary layer to that of the zeroth layer is equal to the ratio of the respective number densities for that gas. When concentration is dependent on altitude, as in the case of water vapor, the number density ratio is multiplied by the factor of altitude dependence.
The relation between number density and altitude is discussed in the following section. Equation 4 can be easily integrated from a height of 0 to z to obtain:.
Again, using Eq. The subscript 0 denotes the value for the zeroth layer. The number density of a well-mixed greenhouse gas n z is related by the number density of the atmosphere:. For the three gases CO 2 , CH 4 , and N 2 O that have concentrations roughly independent of altitude, the ratio of number density is as follows:.
In the case of water vapor where the concentration changes with the altitude, Eq. To obtain the change of outgoing energy flux density at the tropopause, it is necessary to calculate the radiative transfer of terrestrial radiation.
The first term on the right-hand side of Eq. The second term is blackbody radiation based on the Kirchhoff law, which states that emittance and absorption have identical values. Scattering by molecules is ignored since the reference radiation is located in the infrared region. Therefore, the net change in flux density is expressed as a function of altitude as follows:. Taking into account the absorption by the four kinds of molecules, the actual change of the flux density passing through the layer is.
The absorption spectra of greenhouse gases are discussed in the following section. They are summed up for the reference range of wavelengths to give the total flux density. Of course, the total absorption through any layers must not be greater than one. The calculations of radiative forcing require the absorption spectra of the four greenhouse gases for the zeroth layer in Absorption spectra of atmospheric greenhouse gases in for thickness of m obtained from the SpectralCalc website: a water vapor, ppmv; b CO2, ppmv; c CH4, 0.
The concentration of water vapor is assumed to be the same as the present value. Absorption is the intensity ratio of absorbed radiation to total radiation incident on the zeroth layer. Figure 2 shows the absorption spectra of the zeroth layer for , as calculated using the SpectralCalc database. For selected gases, the SpectralCalc website provides transmittance spectra at an arbitrary pressure, temperature, and thickness of a gas layer; the concentration of the gas in the layer; and the range of wavelengths.
The concentrations are ppmv for water vapor, ppmv for CO 2 , 0. The pre-industrial concentration of water vapor is assumed to be the same as the present value. The unit spectral interval is set to 1 nm. The numerical values used for the calculations are as follows:. Figure 3 shows the calculated outgoing spectra in the pre-industrial era at altitudes of 3 km, 6 km, 9 km, and 11 km the tropopause. The former is due to water vapor and the latter is due to CO 2.
In both these ranges, the absorption is nearly one. However, the outgoing flux in these ranges is not zero because of emission from the greenhouse gases. Moreover, the intensity of the flux decreases with altitude.
The red area under the spectrum at 11 km, The growth rates of greenhouse gas concentrations from the pre-industrial era to are given as follows: CO 2 , 1. For simplicity, we assume that the absorption spectrum in may be approximated by multiplying the spectrum in by the growth rate. The absorption values never exceed one.
Outgoing terrestrial radiation spectrum at 3 km blue , 6 km green , 9 km yellow , and 11 km tropopause; red in , as calculated using the spectra shown in Figure 2. A similar calculation in which the absorption spectrum of only ppmv CO 2 is replaced with that of Therefore, the radiative forcing of CO 2 for the period between and is. The radiative forcing of each greenhouse gas is listed in Table 2.
Figure 4 shows the distribution of radiative forcing. The robustness of the proposed model must be confirmed by testing the sensitivity of the results to changes in certain parameters. A change in water vapor concentration does not affect the radiative forcing considerably. Moreover, the outgoing flux density decreases as the lapse rate increases.
There are some sources of the uncertainties in this calculation. The first is assuming that the absorption spectra of greenhouse gases in each layer are proportional to only their number density. However, the absorption spectrum also changes with pressure and temperature in the layer: absorption line width broadening is caused by the thermal motion of the molecules and the collisions between them, both of which depend on pressure and temperature.
However, the effects of the other layer are approximated as the effects of the zeroth layer for simplicity. These differences in the spectra in each layer will produce uncertainties in the outgoing fluxes. The second source of uncertainty is ignoring the radiative transfer of incident solar radiation in the near-infrared region.
The absorption and emission at 2. Therefore, the outgoing flux contains some uncertainties. Figure 5 shows the calculated radiative forcing for each increasing greenhouse gas from the pre-industrial era to the present age. Calculated radiative forcings for increasing concentrations of greenhouse gases: a CO2, for every 20 ppmv from ppmv to ppmv; b CH4, for every 0.
Global Warming 101
A greenhouse gas sometimes abbreviated GHG is a gas that absorbs and emits radiant energy within the thermal infrared range, causing the greenhouse effect. The vast majority of anthropogenic carbon dioxide emissions come from combustion of fossil fuels , principally coal , petroleum including oil and natural gas , with additional contributions coming from deforestation and other changes in land use. 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 or solubility. Therefore, they do not contribute significantly to the greenhouse effect and often are omitted when discussing greenhouse gases. Greenhouse gases are those that absorb and emit infrared radiation in the wavelength range emitted by Earth.
Before we dig deep into the causes of greenhouse effect, it is important for us to know what is greenhouse effect. You must have heard of greenhouse effect during any debate on global warming. The light that we get from the sun helps to keep this planet warm. It can be used to produce solar energy, drying clothes, or by plants in the process of photosynthesis. The absorption of these radiations by greenhouse gases makes it possible to keep this planet warm for humans. Without Greenhouse effect, the temperature of this planet would be lesser by 30 degree Celsius and this would be too cold for us to survive. Greenhouse effect is not bad.
The greenhouse effect
Glaciers are melting , sea levels are rising, cloud forests are dying , and wildlife is scrambling to keep pace. It has become clear that humans have caused most of the past century's warming by releasing heat-trapping gases as we power our modern lives. Called greenhouse gases, their levels are higher now than at any time in the last , years. We often call the result global warming, but it is causing a set of changes to the Earth's climate, or long-term weather patterns, that varies from place to place.
For the warming over the last century, there is no convincing alternative explanation. Global data show that was the warmest year on record and the third consecutive year for record global average surface temperatures. The emission of greenhouses gases GHGs , 6 which move about in the atmosphere, is a major cause of global climate change. Even with drastic GHG reductions, almost half of humans will face deadly heat. Although a number of U.
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Greenhouse gases are crucial to keeping our planet at a habitable temperature. The greenhouse effect: some of the infrared radiation passes through the atmosphere, but most is absorbed and re-emitted in all directions by greenhouse gas molecules and clouds. A greenhouse gas is so called because it absorbs infrared radiation in the form of heat, which is circulated in the atmosphere and eventually lost to space. Greenhouse gases also increase the rate at which the atmosphere can absorb short-wave radiation from the sun, but this has a much weaker effect on global temperatures. The contribution that a greenhouse gas makes to the greenhouse effect depends on how much heat it absorbs, how much it re-radiates and how much of it is in the atmosphere. In terms of the amount of heat they can absorb and re-radiate known as their global warming potential or GWP , methane is 23 times more effective and nitrous oxide times more effective than carbon dioxide.
Jump to navigation. And yes, it's really happening. Over the past 50 years, the average global temperature has increased at the fastest rate in recorded history. And scientists say that unless we curb global-warming emissions, average U. Normally, this radiation would escape into space—but these pollutants, which can last for years to centuries in the atmosphere, trap the heat and cause the planet to get hotter. That's what's known as the greenhouse effect.
В это святилище существует очень мало входов, и ТРАНСТЕКСТ - один из. Система Сквозь строй должна служить его верным часовым, а Стратмору вздумалось ее обойти. Чатрукьян слышал гулкие удары своего сердца. ТРАНСТЕКСТ заклинило на восемнадцать часовМысль о компьютерном вирусе, проникшем в ТРАНСТЕКСТ и теперь свободно разгуливающем по подвалам АНБ, была непереносима. - Я обязан об этом доложить, - сказал он вслух. В подобной ситуации надо известить только одного человека - старшего администратора систем безопасности АНБ, одышливого, весящего четыреста фунтов компьютерного гуру, придумавшего систему фильтров Сквозь строй. В АНБ он получил кличку Джабба и приобрел репутацию полубога.
Можешь представить себе последствия, если бы это обнаружилось, когда Попрыгунчик был бы уже внедрен. - Так или иначе, - парировала Сьюзан, - теперь мы имеем параноиков из Фонда электронных границ, уверенных, что черный ход есть во всех наших алгоритмах. - А это не так? - язвительно заметил Хейл.
ГЛАВА 59 Сьюзан протянула руку, и коммандер Стратмор помог ей подняться по лестнице в помещение шифровалки. А перед глазами у нее стоял образ Фила Чатрукьяна, его искалеченного и обгоревшего тела, распростертого на генераторах, а из головы не выходила мысль о Хейле, притаившемся в лабиринтах шифровалки. Правда открылась со всей очевидностью: Хейл столкнул Чатрукьяна. Нетвердой походкой Сьюзан подошла к главному выходу- двери, через которую она вошла сюда несколько часов. Отчаянное нажатие на кнопки неосвещенной панели ничего не дало: массивная дверь не поддалась.
Она посмотрела на него, потом на кольцо.