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The average global temperature has risen about 0.50C in the last century, and scientists expect another increase of 1 to 40C in the next 100 years due to increasing pollution in our atmosphere.
* Greenhouse gases allow the passage of incoming solar short-wavelength radiation but absorb some of the reflected infrared radiation and reradiate it back to the Earth’s surface.
* Energy is then reradiated in the lower atmosphere causing an increase in temperature and climatic change. Hence, contributing to global warming.
1. Water (H2O)
2. Carbon dioxide (CO2)
3. Methane (CH4)
4. Nitrous oxide (N2O)
6. Ozone (O3)
Greenhouse Gas Sources:
1.Combustion of hydrocarbons
1.Evaporation of oceans and lakes
2. Forest fires
2.Decay of organic matter.
3.Natural forest fires
4.Natural gas production
Decay of organic matter-
1.Use of nitrogen based fertilizers.
2.Combustion of biomass.
1.Secondary pollutant in photochemical smog’s
Greenhouse Gas Effects:
Greenhouse gas effects depend on both their concentration (abundance) in the atmosphere and on their ability to absorb heat radiation.
However, each molecule has its own type of bond, they each absorb at slightly different frequencies and wavelengths.
Heat trapping effectiveness compared with CO2
Overall contribution to increased global warming.
10,000 – 25,000
1. Water= has the most over all contribution to global warming as it has a high concentration.
2. Carbon dioxide= is the most important green house gas as contributes 50% to global warming and has second largest concentration.
3. CFCs= are thousands of times better at absorbing heat/ infrared radiation than CO2 – BUT they have a lower concentration; hence, their effect is limited to 14%.
Greenhouse effect is determined by:
* Concentration of chemical
* Lifespan of chemical.
* Ability to absorb infrared radiation
* Intensity of absorption
* Number of wavelengths absorbed depends on the molecules bonds.
‘Atmospheric Window Region’ = is the region within the spectrum through which radiation can escape.
Methane and CFCs have a greater greenhouse factor than CO2 and H2O because they absorb in the ‘atmospheric window region’.
CFC fills this window.
Methane is 30x more effective in its green house effect as it has 4 C-H bonds, which means it can absorb more at a certain frequency.
Influence of Gases on Global Warming:
1. Increase in temperature by about 0.5 degree.
2. Increase in precipitation
3. Rise in sea levels- melting of glaciers/ ice caps/ thermal expansion of water
4. Changes in crop yields
5. More severe droughts
6. More floods and storms
7. Changes in distribution of pathogens and insects (e.g. malaria).
Influence of Particulates on Temperature:
1. Particulates= volcanic dust.
2. It scatters and reflects incoming sunlight (UV and visible) so less solar radiation can enter the atmosphere.
3. It lowers atmospheric temperature as provides condensation nuclei around which water particles condense to form clouds reducing solar heating.
4. Volcanic eruptions & forest fires- increases number of particulates.