Pollution

Fossil fuels – greenhouse gases and the greenhouse effect.

The ‘greenhouse effect’

• Most people regard the ‘greenhouse effect’ as one of the most serious environmental issues facing the earth.
  (To find out more about this effect, see the Climate change section)

• In fact, the ‘greenhouse effect’ is a natural way to trap in heat by gases such as carbon dioxide and methane.
• These gases are in the atmosphere and allow short-wave radiation but trap some of the long-wave radiation trying to escape, thus acting like the glass of a greenhouse .
• Without this effect, the earth would have an average temperature of minus 17^oC
• To understand how the greenhouse effect works,  view this animation.

Why are there concerns?

• The problem is that over the last few hundred years human activity has dramatically increased the quantities of these gases in the atmosphere, making the effect far more efficient at retaining heat.
• This 'enhanced'  effect has been made worse by new ‘man-made’ gases which contribute to this effect (anthropogenic gases).
• Although we are not certain, some scientists predict that there will be an average global temperature rise by 0.3^oC every decade. This is investigated in more detail in the climate change section.
• Some of these gases have a greater ability to retain radiation than others: e.g. one CFC (chloroflurocarbon) molecule is 5000 times more effective at reflecting radiation than one molecule of carbon dioxide.

The greenhouse gases:

The following table shows the major ‘greenhouse’ gases that have contributed to the ‘enhanced’ greenhouse effect. Water vapour, which is not included in the table, has the greatest greenhouse effect but it is not significantly affected by human activity.

ppm – parts per million

Solutions:

Solutions to the increase in ‘greenhouse’ gases is investigated in more detail in the ‘Climate change’ section.

 Acid rain