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Here is a compilation of term papers on ‘Solar Radiation and Global Warming’ for class 8, 9, 10, 11 and 12. Find paragraphs, long and short term papers on ‘Solar Radiation and Global Warming’ especially written for school and college students.
Term Paper on Solar Radiation and Global Warming
Term Paper Contents:
- Term Paper on the Introduction to Solar Radiation and Global Warming
- Term Paper on Solar Radiation
- Term Paper on the Solar Radiations and Radiative Transfer of Energy
- Term Paper on the Effective Temperature of the Planet by Solar Emission
- Term Paper on Solar Constant and Solar Irradiance
- Term Paper on Solar Luminosity
- Term Paper on the Solar Irradiance and Global Warming
- Term Paper on the Atmospheric Effects on Incoming Solar Radiation
- Term Paper on the Absorption of Radiation by the Atmosphere and Heating Effect
- Term Paper on Reflectivity or Albedo
- Term Paper on the Distribution of Incoming Solar Energy
- Term Paper on External Forcing and Climate Change
- Term Paper on Solar Luminosity
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Term Paper # 1. Introduction to Solar Radiation and Global Warming:
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The temperature is a predominant factor in the atmospheric divide in five layers. Again the temperature is found to be responsible for three major air circulation systems creating six different climate zones extending from equator to poles in both north and south. The source of heat for atmospheric temperature rise is the Sun.
The high energy solar radiations travel through space to the planet’s atmosphere before striking the surface. The heat absorbed from the solar beam by the atmosphere and the Earth’s surface leads to global warming.
The characteristic features of solar beam and its heat transfer processes to the Earth and the atmosphere.
The heat source for global heating is the Sun, which is a huge gas mass at an extremely high temperature. Solar radiation originates from nuclear fusion reaction and it takes less than ten minutes for the solar beam to strike the Earth’s surface. Solar radiation consists of ionizing radiations and non-ionizing beams.
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The highly injurious ionizing radiations are filtered out by upper atmosphere, allowing only non-ionizing part to reach the Earth. The non-ionizing radiation consists of three bands, viz., ultra-violet (UV), visible and infra-red. The infra-red portion of the radiation generates most of the heat through absorption by some of the atmospheric gases, such as, carbon-dioxide.
The total quantity of incoming solar radiation depends on solar constant, solar irradiance and solar luminosity. The one-fourth of the solar constant, which is around 340 Watts per square metre reaches the Earth. However, of the total incoming radiation, around 30% is reflected back by surface, clouds, and particulate and the rest 70% is used in processes like melting ice, evaporating water, photosynthesis, absorption by cloud and atmospheric gases. Only 19% of solar energy is available for absorption by atmospheric greenhouse gases.
The solar beams striking the Earth cause the atmospheric temperature to rise. The variations in temperatures in different regions occur due to the different angles at which the solar beams strike the Earth’s surface, The beam striking at 90° transmit the highest level of energy. Therefore the hottest places on earth are those areas where the rays of the sun arrive at right angles. Other locations, where the sun’s rays hit at lesser angles, tend to be cooler.
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Solar radiation is also responsible for evaporation, and consequently the hydrological cycle and the ocean currents. Solar radiation is responsible for photosynthesis, thus the carbon cycle. Hydrological and carbon cycles determine the quantities of heat (infra-red) absorbing water vapor and carbon dioxide present in the atmosphere and thus the quantum of heating. Among the factors responsible for climate change due to external forces, are variations in the earth s orbit around the Sun, and changes in solar luminosity.
The surface features of the sun are normally classified into three regions. The three regions are known as the photosphere, chromosphere, and corona. The photosphere corresponds to the bright region normally visible to the naked eye. About 3,100 miles (5,000 km) above the photosphere is the chromosphere, from which short-lived, needle-like projections may extend upward for several thousands of kilometers.
The corona is the outermost layer of the Sun; this region extends into the regions of the planets. Most of the surface features of the Sun lie within photosphere, though a few extend into the chromosphere and even the corona. The visible radiation (light) comes from photosphere.
Term Paper # 2. Solar Radiation:
Solar radiation originates from a nuclear fusion reaction in the sun, forming ionizing radiations (X-rays and gamma-rays) and nonionizing radiations.
Fortunately, the highly injurious ionizing radiation does not penetrate the Earth’s atmosphere. The non-ionizing part can permeate through the upper atmosphere.
The spectral range of non-ionizing solar radiation (fig.3.1 A) is commonly divided into three regions or bands on the basis of wavelength as follows:
1. Visible:
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The spectral band wavelength extends from 400 to 700nm. White light consists of seven colors in the beam, viz., violet, indigo, blue, green, yellow, orange and red. These are spread over a range of wavelength from violet at 400nm (0.4 im) to red at 700nm (0.7 im). Before violet on the short wavelength side is ultra violet (UV). After red are infra-red (IR) rays, which have a longer wave length than red. Radiation in the visible range is not absorbed by the atmosphere.
2. Ultra-Violet:
UV rays are comprised of short wavelength solar radiation, in the range of 100-400 nm (0.001-0.4 μm). This wavelength range is lower than violet, on the extreme left of visible range, and hence known as ultra violet. UV rays are invisible. It is again divided into 3-components, based on its biological effects (Fig.3.1B).
These are known as UV-A, black light; UV-B, sunburn or erythermal radiation; UV-C, germicidal radiation. Due to the harmful biological effects of UV radiation, it can harm people. The ozone layer, however, blocks most of the UV rays and prevents it from reaching the earth’s surface. The depletion of ozone layer by fluorocarbon gases can increase the UV on the Earth.
3. Infra-Red:
Infra-red is invisible, and covers the spectral range of 700 to 14,000 nm (,0.7-100 µm). Infra-red portion of the radiation generates most of the heat through absorption by atmospheric gases.
Term Paper # 3. Solar Radiations and Radiative Transfer of Energy:
Solar beams provide the energy required to propagate and sustain life on the Earth. The Sun is a huge gas mass, with core temperature of 5,500’K, at a distance of about 150 million kms and it takes approximately 10 minutes for sunlight to reach us. Solar beam provides the light and heat, by permeating through the atmospheric layers and finally striking the Earth’s surface.
The transfer of thermal energy or heat of the solar beams in the form of the electromagnetic wave can occur through conduction, convection and radiation. Major heat transfer occurs by radiation. In ideal conditions, a substance absorbs all the energy impinging on it from solar beam and becomes a ‘black body’. The black body itself then becomes a radiation source, where incoming radiation balances the outgoing one.
The wavelength of propagation depends on the temperature of the emitting body, and the basic equation governing the relation between wavelength and temperature is given by Planck’s Law:
Eλ* = c1/ {λ 5 [exp.(c2/λT) – 1]}
Where Eλ* = amount of energy (W m-2 µm-1) emitted at wavelength λ (µm) by a body at a temperature of T in degree Kelvin c1 and c2 are constants. By plotting wavelength against energy flux, “bell-shaped” curve results, showing energy distribution over a range of wavelength. However, the energy of solar radiation over the entire range of wavelength i.e., 0.001 to 100 µm follows the Gaussian distribution pattern and thus sharply centered on the wavelength band of 0.2-2 µm.
By integration of the area under the Planck’s curve, the total energy (E) emitted by a black body is found to be directly proportional to the fourth power of the absolute temperature (T).
The resultant equation is known as Stefan – Boltzman Law is as follows:
E = σ T4
Where σ = Stefan – Boltzman constant = 5.67 × 10 -8 W m -2 K -4
The total solar input to space assuming a temperature of 5760 K for the sun becomes 3.84 × 10 26 Watts. However, only a small fraction is intercepted by the Earth, primarily due to the fact that the energy received is inversely proportional to the square of the solar distance (150 million Km).
By differentiation of Planck’s equation, the equation relating wave length and temperature is obtained, which is as follows:
λ max = 2897/T
The above equation is known as Wien’s Law. According to Wien’s equation the maximum energy wavelength is inversely related to temperature. The equation indicates the maximum emission wavelength for the Sun and the Earth are 0.50 and 11.4 µm respectively. The intense solar radiation is mainly in shortwave range of 0.2 to 4.0 nm, with maximum emission at 0.5 nm. The weaker terrestrial radiation is in the range of 4 to 100 micron with a peak at about 10 nm.
Of the 99% of solar energy emitted is in the range from ultra violet to infrared. According to theoretical calculations, based on Planck’s law, the shares of ultraviolet, visible and infra-red are 9%, 45%, and 46% respectively.
The 46% of the solar radiation in the infra-red range is available for absorption by greenhouse gases. Anthropogenic greenhouse gases constitute the main source for providing extra heat to the Earth’s atmosphere than that provided by omnipresent greenhouse gases formed by natural processes.
Term Paper # 4. Effective Temperature of the Planet by Solar Emission:
Climate Model:
By denoting the solar radiative flux at the top of the planet’s atmosphere by So (for solar constant), the Earth’s average albedo by a, and planet’s radius as R the area of that disk is π R2.
Heat absorbed by planet = (1 – a) π R2S
The total heat radiated from the planet is equal to the energy flux implied by its temperature, Te (from the Stefan-Boltzmann law) times the entire surface of the planet or:
Heat radiated from planet = (4 π R2) σ T4
Radiative balance can therefore be written as follows:
(4 π R2) σ Te4 = (1 – a) π R2So
This is a very simple model of the radiative equilibrium of the Earth.
Solving this equation for temperature we obtain:
Te = [(1-a)So / 4σ]1/4
The equation above yields an average earth temperature of 288°K (15 °C; 59 °F)(2a). The above equation represents the effective radiative temperature of the Earth (including the clouds and atmosphere).The use of effective emissivity and albedo account for the greenhouse effect. With this temperature the Earth radiation will be centered on a wavelength of about 11 µm, well within the range of infra-red (IR) radiation.
The Earth and other planets are not perfect black bodies, as they do not absorb all the incoming solar radiation but reflect part of it back to space. The ratio between the reflected and the incoming energies is termed the planetary albedo.
Term Paper # 5. Solar Constant and Solar Irradiance:
The solar constant is the average amount of incoming solar radiation per unit area, falling on the outer surface of Earth’s atmosphere, in a plane perpendicular to the rays. Solar constant is approximately 1,367 watts per square meter. As the earth-based measurements of the quantity are not accurate, due to variations in the earth’s atmosphere, scientists rely on satellites to make these measurements.
Although referred to as the solar constant, this quantity has actually been found to vary since careful measurements were made in 1978. In 1980, a satellite-based measurement yielded the value of 1,368.2 watts per square meter. Over the next few years, the value was found to decrease by about 0.04% per year. Such variations have now been linked to several physical processes known to occur in the Sun’s interior.
Solar Irradiance:
Solar irradiance, or insolation, is the amount of sunlight which reaches the Earth. From the Earth, it is only possible to observe the radiant energy emitted by the Sun in the direction of our planet. Irradiance is evaluated through measurements of optical brightness, total radiation, or radiation in various frequencies. Both the radiation reaching the upper atmosphere and that to the Earth’s surface makes up the total irradiance.
The gases in the atmosphere absorb some solar radiation at different wavelengths. The clouds and dust also affect the solar irradiance. The average incoming solar radiation or the solar irradiance, taking into account the half of the planet not receiving any solar radiation at all, is one fourth the solar constant or ~342 W/m2. At any given location and time, the amount received at the surface depends on the state of the atmosphere and the latitude.
Term Paper # 6. Solar Luminosity:
The total radiant energy emitted from the Sun in all directions is a quantity known as solar luminosity. The luminosity of the Sun has been estimated to be 3.8478 × 1026 watts. Some scientists believe that long-term variations in the solar luminosity may be a better correlation to environmental conditions on Earth than solar irradiance, including global warming. Variations in solar luminosity can occur due to stellar rotation, convection and magnetism.
The measurements of total solar irradiance, taking into account the solar flux contributions over all wavelengths, provide a more accurate value than total luminosity because of the short time variations of certain regions of solar spectrum. Short-term variations in solar irradiation vary significantly with the position of the observer particularly more on ground based measurements. However satellite based measurements give accuracy within few parts per million, allowing scientists to acquire a better understanding of variations in the total solar irradiance.
Variations in solar irradiance have been attributed to the solar phenomena, such as, oscillation, granulation, sunspots, faculae, and solar cycle.
Oscillations arise from the action of resonant waves trapped in the Sun’s interior. At a given time, there are tens of millions of frequencies represented by the resonant waves, but only certain oscillations contribute to variations in the solar irradiance, lasting for few minutes (about 5 minutes).
Granulation produces solar irradiance variations lasting about 10 minutes. It is closely related to the convective energy flow in the outer part of the Sun’s interior. To the observer on Earth, the surface of the Sun appears to be made up of finely divided regions known as granules, separated by dark regions. Each of these granules makes its appearance for about 10 minutes and then disappears. These granules are believed to be the centers of rising convection cells.
Sunspots give rise to variations that may last for several days, and sometimes as long as 200 days. They actually correspond to regions of intense magnetic activity where the solar atmosphere is slightly cooler than the surroundings. Sunspots appear as dark regions on the Sun’s surface to observers on Earth. The reduction in the total solar irradiance has been attributed both to the presence of these sunspots and the formation of newly formed active regions associated with large sunspots, or with rapidly evolving, complex sunspots.
Faculae, producing variations that may last for tens of days, are bright regions in the photosphere where high-temperature interior regions of the Sun radiate energy. They tend to congregate in bright regions near sunspots, less dense than the surroundings, forming solar active tube-like regions defined by magnetic field lines. The radiation from hotter layers below the photosphere can leak through the walls of the faculae, thus producing an atmosphere that appears hotter, and brighter, than others.
Solar cycle is responsible for variations in the solar irradiance that have a period of about 11 years. This 11-year activity cycle of sunspot frequency is actually half of a 22-year magnetic cycle, which arises from the reversal of the poles of the Sun’s magnetic field. From one activity cycle to the next, the north magnetic pole becomes the south magnetic pole, and vice versa.
Solar luminosity has been found to achieve a maximum value at the very time that sunspot activity is highest during the 11-year sunspot cycle. Surprisingly, the Sun’s rotation, with a rotational period of about 27 days, does not give rise to significant variations in the total solar irradiance. This is because its effects are overridden by the contributions of sunspots and faculae.
Term Paper # 7. Solar Irradiance and Global Warming:
The long-term solar irradiance variations may contribute to global warming over decades or hundreds of years. In recent times, there has been speculation that changes in total solar irradiation have amplified the greenhouse effects, i.e., the retention of solar radiation and gradual warming of the earth’s atmosphere.
Some of these changes, particularly small shifts in the length of the activity cycle, seem to correlate rather closely with climatic conditions in pre- and post-industrial times. However any major effect of variations in solar irradiance on global warming over the past 150 years remains highly controversial.
Term Paper # 8. Atmospheric Effects on Incoming Solar Radiation:
Solar radiation is partially depleted and attenuated as it traverses the atmospheric layers, preventing a substantial portion of it from reaching the Earth’s surface. This phenomenon is due to absorption, scattering, and reflection in the upper atmosphere (stratosphere), with its thin layer of ozone, and the lower atmosphere (troposphere), within which cloud formations occur and weather conditions manifest themselves.
The stratospheric ozone layer has a strong absorption affinity for solar UVR, depending on wavelength. Depletion of the protective ozone layer beyond the critical level by certain atmospheric pollutants (fluorocarbons and nitrogen oxides) shall promote the transmission of highly injurious UVR.
The troposphere is an attenuating medium. Direct solar radiation received by the earth’s atmosphere and surface is modified by atmospheric scatterings. The solar radiation is reflected and scattered primarily by clouds (moisture and ice particles), particulate matter (dust, smoke, haze, and smog), and various gases.
The diffused solar radiation received by earth’s surface is that has been modified by atmospheric scattering. The two major processes involved in troposphere scattering are determined by the size of the molecules and particles and are known as selective scattering and nonselective scattering.
The amount of scattering that takes place is dependent on two factors wavelength of the incoming radiation and the size of the scattering particle or gas molecule.
The degree of scattering decreases with increasing wavelength in the following order:
UV-B > UV-A > violet > blue > green > yellow > orange > red > infrared.
The presence of a large number of particles with a size of about 0.5 microns in atmosphere, results in shorter wavelengths being preferentially scattered.
Effects of scattering include reduction of the amount of incoming radiation reaching the Earth’s surface and a significant proportion of scattered shortwave solar radiation is redirected back to space. Without scattering in our atmosphere, the daylight sky would be black.
Selective scattering is caused by smoke, fumes, haze, and gas molecules that are either equal to or smaller than the wavelength of incident radiation. Selective scattering is severe when atmosphere is extensively polluted. Selective scattering in the blue region of the spectrum by smaller molecules under clear-sky conditions accounts for the blue sky. The color of the sky is also determined by the length of the atmospheric path traversed by sunlight.
Nonselective scattering is caused by dust, fog, and clouds with particle sizes more than 10 times the wavelength of the incident radiation. As scattering in this case is not wavelength-dependent, it is equal for all wavelengths, i.e., to all colors. This factor causes the clouds to appear white.
Term Paper # 9. Absorption of Radiation by the Atmosphere and Heating Effect:
Absorption is defined as a process in which solar radiation is retained by a substance and converted into heat energy. Visible range is not absorbed by atmospheric gases. Spectral irradiance in visible wavelength varies from 1.7W/m2/nm at the top of the atmosphere, to 0.4 W/m2/nm at sea level where it is not absorbed by atmospheric gases.
Only Infrared spectrum with irradiance of 0.7 W/m2/nm is absorbed by H2O. 1R spectrum with irradiance of 0.1 W/m2/nm is absorbed by CO2 and H2O. at sea level. The radiation in the wavelength range of approx. 2000 to 2500 nm in the infrared is totally absorbed by CO2 at the sea level.
Term Paper # 10. Reflectivity or Albedo:
As in the atmosphere, some of the radiation received at the Earth’s surface is redirected back to space by reflection. The reflectivity or albedo of the Earth’s surface varies with the type of material that covers it. For example, fresh snow can reflect up to 95% of the solar beams that reaches it surface. Some other surface reflectivity’s include, dry sand 35 to 45%, broadleaf deciduous forest 5 to 10%, needle leaf coniferous forest 10 to 20%, and grass type vegetation 15 to 25%.
The albedo at two levels, viz., the Earth’s surface and the top of the atmosphere, are of great importance. The top of the atmosphere one is known as planetary albedo helps in understanding of large scale climate processes. The surface albedo depends largely on the nature of the surface and has significant effect on local climate. The Earth’s average albedo, reflectance from both the atmosphere (planetary albedo) and the surface (surface albedo), is about 30%. The other albedo, the cloud albedo, plays an important role in the atmospheric heating and thus has influence on local climate.
Term Paper # 11. Distribution of Incoming Solar Energy:
Of all the total incoming sunlight that passes through the atmosphere annually, 51% is available at the Earth’s surface to do works, such as:
(i) Heat the Earth’s surface at lower atmosphere,
(ii) Melt ice and evaporate water, and
(iii) Run photosynthesis in plants.
These are essential functions to maintain natural ecological cycles, such as hydrological and carbon cycles.
The remaining 49% of solar beams is distributed as follows:
i. 4% is reflected back to space by the Earth’s surface,
ii. 26% is scattered or reflected to space by clouds and atmospheric particles and
iii. 19% is absorbed by atmospheric gases, particles, and clouds.
Average incoming solar radiation is around 342 watts per sq.meter.
The distribution of solar energy in various functions is as follows:
i. 51% absorbed by surface amounts to i74.4 W per sq.meter
ii. 19% absorbed by atmosphere equals to 64.98 W/sq.meter.
iii. 30% reflected beams account for rest 102.6 W/sq.meter Reflections include by atmosphere as 6% or 20.52W/ sq.meter, by cloud as 20% or 68.40 W/sq.meter and by surface as 4% or 13,68 W/sq.meter.
The 19% of solar beam absorbed by atmospheric gases, mainly carbon dioxide, plays the key role in global atmospheric warming. Deforestation leads to less absorption of solar beam required by plants for photosynthesis. Deforestation and higher rates of carbon dioxide emission shall cause accelerated heating of the atmosphere by incoming solar beams.
If the 51% of solar energy amounting to 174.4 W per sq.meter absorbed by the Earth’s surface can be utilized for power generation, then there would be no need to burn fossil fuel to generate energy. In such circumstances, there would not be any enhanced rate of global warming from anthropogenic emissions.
The intensity of sunlight at ground level varies with latitude, geographic location, season, cloud coverage, atmospheric pollution, elevation above sea level, and solar altitude. Efforts to harness the solar energy in high intensity areas, such as, deserts for power generation is already on the anvil.
Term Paper # 12. External Forcing and Climate Change:
Radiative Forcing:
The energy budget of the Earth is considered to be in equilibrium, maintains a balance between incoming solar radiation and outgoing terrestrial radiation over the long term. Radiative forcing is defined as the change in the balance between solar radiation entering the atmosphere and the Earth’s radiation going out.
The heat balance of the atmosphere is liable to change due to changing heat absorption capacities (e.g., greenhouse gases) and heat reflection abilities (e.g., albedo) of the materials. The imbalance causes changes in global temperatures. On average, a positive radiative forcing tends to warm the surface of the Earth while negative forcing tends to cool the surface.
The concept of radiative forcing is useful because a linear relationship has been determined between the global mean equilibrium surface temperature changes and the amount of RR The radiation balance can be altered by factors such as intensity of solar energy (solar irradiance), reflection by clouds or gases (albedo), absorption by various gases or surfaces (greenhouse gases), and emission of heat by various materials (volcanic eruptions). Any such alteration is a radiative forcing, can cause a new balance to be reached.
Climate responds to several types of external forcing, such as radiative forcing due to changes in atmospheric composition (mainly greenhouse gas concentration), variations in Earth’s orbit (orbital forcing), changes in solar luminosity, and volcanic eruptions. The contributions of the some major components of radiative forcing as assessed by 1PCC in 2005 are shown in fig.3.3.
Orbital Forcing:
The 23.5° tilt of the Earth’s axis affects the angle of incidence of solar radiation on the earth’s surface and causes seasonal and latitudinal variations in day length. The slow changes in the tilt and the shape of the orbit (Milankovitch cycle) cause changes in climate, a process known as orbital forcing. These orbital changes alter the total amount of sunlight reaching the Earth by up to 25% at mid- latitudes (from 400 to 500 Wm-2 at latitudes of 60 degrees).
The net radiative forcing due to anthrpogenic components amounts to around (+)1.82W/mm.sq (Fig.3.3).Land use change (including urbanization, deforestation, reforestation, desertification, etc.) can have significant effects on radiative forcing (and the climate) at the local level by changing the reflectivity of the land surface (or albedo).
Term Paper # 13. Solar Luminosity:
Solar radiation is unevenly distributed throughout the world because of such variables as solar altitude (associated with latitude and season) and atmospheric conditions (cloud coverage & degree of pollution). At high altitudes, the intensity of UVR is significantly higher than at sea level. The spectral distribution of solar energy at sea level is roughly 3, 44, and 53% in the UV, visible, and infrared regions, respectively.
The most favorable belt (15-35° N) encompasses many nations in northern Africa and southern parts of Asia. This belt receives over 3000 hours per year out of 4380 (365 × 12) hours total sunshine with the limited cloud coverage. More than 90% of the incident solar radiation comes as direct radiation.
The moderately favorable belt (0-15° N), or equatorial belt, has high atmospheric humidity and cloudiness that tend to increase the proportion of scattered radiation. The global solar intensity is almost uniform throughout the year as the seasonal variations are only slight.