مروری بر مهار و نیروهای محرکه در ارتباط با گرمایش جهانی
Global Warming and Greenhouse Gases
Heat Retention Mechanism
Natural Events
Anthropogenic Emissions
Temperature Rise
Oceans and Marine Life
Extreme Weather Events
CONCLUSION
LITERATURE CITED
Heat Retention Mechanism
The solar radiation spectrum consists of three wavelength ranges; ultraviolet range, visible range and infrared range and each range possess a portion of the solar energy. Figure 1 shows the components of the extraterrestrial solar radiation spectrum and the fraction of the solar energy in each range. Infrared waves carry almost half of the solar energy in the spectrum, most of these infrared waves are with high wavelength due to the sun surface temperature (5777 K) [5,6]. As the sun radiation goes through the atmosphere, minor portions of it get absorbed by the GHGs and reflected toward the space due to clouds and aerosols. Carbon dioxide and methane absorb the waves in the infrared region, while ozone absorbs the waves in ultraviolet region. Moreover, the absorption effect of water vapor is distributed throughout all the wave lengths [7]. The major portion of solar radiation hits the earth’s surface and the terrestrial objects causing a rise in the temperature of these objects. As the earth’s surface and terrestrial objects get warmer they radiate short-wave infrared radiation (due to their low temperature (277 K) compared with the sun) toward the atmosphere, which will be absorbed by GHGs [4]. Figure 2 shows the extraterrestrial and terrestrial wavelength spectrum and the characteristics of water vapor and carbon dioxide to absorb radiant energy at short-wave infrared region.
Natural Events
The climate of the earth has changed many times in the past with causes related to nature like the variation in the solar radiation emitted by the sun, the volcanic eruptions, and the variation in the incident solar radiation on earth due to Milankovitch cycle [8,9]. Milankovitch cycle is defined as a long-term cycle that occurs every 10,000 years, this cycle launches natural global cooling and warming by three causes: the eccentricity, the obliquity, and the precession. The eccentricity is defined as the change in the elliptical shape of the earth’s orbit while the obliquity is defined as the change in the declination angle of the earth and the precession is defined as the wobble of earth’s axis [10].