C13

• The greenhouse gases: carbon dioxide, water vapour and methane
• increased amount of methane in air is due to more animal farming and increased waste
• main reason for increase in CO2 in atmosphere: burning of fossil fuels
• Scientsits think that intense volcanic activity released gases that formed early atmosphere
• early atmosphere was mainly CO2 and some water vapour,nitrogen gas, methane,ammonia
• volcanic activity released water vapour and as earth cooled down, water vapour in atmosphere condensed to form oceans
• when pure hydrocarbons burn completely they are oxidised to CO2&H2O
• In limited supply of air, incomplete combustion produce CO, some unburnt hydrocarbons & particulates containing soot
• Particulates can cause global dimming as they prevent some sunlight reaching Earth's surface.
• sulfur dioxide and nitrogen oxides cause acid rain & breathing problems
• Atmosphere is now 0.04% CO2,78% nitrogen, 21% oxygen & 1% of other gases like water vapour &noble gases
• CO2 decreases by photosynthesis and dissolving in oceans
• carbon is locked up in sedimentary rocks
• Methane allows shorter wavelength radiation from sun to pass through which is remitted from earth's surface as longer wavelength radiation which is absorbed by methane in atmosphere