Greenhouse gases
The greenhouse gases trap heat in the atmosphere and warm the planet Earth. The main gases responsible for the greenhouse effect include carbon dioxide, methane, nitrous oxide, and water vapor (which all occur naturally), and fluorinated gases (which are synthetic)
- When shortwave radiation from the sun strikes the Earth’s surface it is absorbed and re-emitted from the surface of the Earth as infrared radiation
- However much of the I.R. energy is trapped inside the Earth’s atmosphere by Greenhouse gases which can absorb and hold the radiation
- Two such gases are carbon dioxide and methane
- They both lead to climate change as they trap heat energy from escaping the Earth’s atmosphere, leading to global warming
Carbon dioxide
- Sources: the main sources of Carbon dioxide are combustion of wood and fossil fuels, respiration of plants and animals, thermal decomposition of carbonate rocks and the effect of acids on carbonates
Methane
- Sources: the main sources of methane are digestive processes of animals, decomposition of vegetation, bacterial action in swamps and in rice paddy fields
The Greenhouse effect
- the main cause due to the increased concentration and effect of Greenhouse gases, mainly methane and carbon dioxide
Carbon Cycle
- The carbon cycle describes the movement of carbon between the seas, land and atmosphere
- In the atmosphere, the main source of carbon is carbon dioxide
Sources of CO2 in the atmosphere
Combustion of fossil fuels, e.g: methane:
CH4 + 202 → CO2 + H2O
Respiration: the production of energy in living things. The overall reaction of respiration is represented by the equation:
C6H12O6 + 6O2 → 6CO2 + 6H2O
- Decomposition of limestone
- Reactions of acids with carbonates
Removal of carbon dioxide from the atmosphere
- Photosynthesis: the process of producing glucose and oxygen from carbon dioxide and water in plants in the presence of chlorophyll and light:
6CO2 + 6H2O → C6H12O6 + 6O2
- Carbon dioxide dissolves in the water in seas and oceans and is removed by shellfish for making their calcium carbonate shells
Balancing the carbon
- The carbon as carbonate, carbon dioxide or organic carbon compounds is present in the sea, the air and under the Earth
- There is a continuous cycle of these compounds between these sources called the carbon cycle
- There is a constant amount of carbon compounds in the sea, atmosphere and under the Earth
- As long as these are balanced, the amount of carbon dioxide in the atmosphere remains constant
- Scientists are worried that increasing the amounts of fossil fuels burned will increase global warming and unbalance the carbon cycle
