A2 Biology- Is the climate changing?

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Causes of global warming


  • The sun radiates energy, mostly as visable light, and the Earth absorbs some of this energy. The Earth warms up and in turn radiates energy back into space as infrared radiation.
  • Some of this energy is absorbed by gases in the atmosphere, warming it.
  • The gases in the atmosphere that stop the infrared radiation from escaping are known as greenhouse gases. They create the greenhouse effect, which keeps the earth warm. 
  • Most solar radiation is absorbed by the earth's surface, which warms up.
  • some is reflected by clouds
  • some visable radiation is reflected by the earth.
  • most UV is absorbed by ozone in the stratosphere. 
  • some infrared is absorbed by greenhouse gases, warming up the troposphere. 
  • some infrared emitted by the earth's surface escapes and cools down the earth. 

Not all gases are greenhouse gases. The 'global warming potential' is a measure of the greenhouse effect caused by that gas relative to the same amount of carbon dioxide over a given time, which is given a value of 1. 

Carbon dioxide is not the worst greenhouse gas in the atmosphere, however it is the most abundant. 

Methane (CH4)

  • produced by anaerobic decay of organic matter in waterlogged conditions, for example in bogs and rice fields.
  • Combustion of landfill sites and decomposition of animal waste are also sources.
  • Incomplete combustion also produces methane. 
  • One molecule of methane absorbs more infrared radiation than a molecule of carbon dioxide.
  • Emissions could be reduced through better waste recycling and by using it as a biofuel.

Does increased carbon dioxide cause global warming?

Theres a correlation between the increase of


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