Environmental change caused by human activity - The greenhouse effect

Without the greenhouse effect the mean temperature on Earth would be -18°C and there would be very little or no life. So the greenhouse effect itself is a good thing. The greenhouse effect traps some of the energy from the Sun, which keeps our planet at a suitable temperature for life.

The problem is that our increased release of greenhouse gases is causing an increase in the greenhouse effect called the enhanced greenhouse effect. This is leading to global warming.

Carbon dioxide, water vapour and methane are amongst the most common greenhouse gases. Since the start of the Industrial Revolution in about 1750 the levels of carbon dioxide have increased by 40%.

Without the greenhouse effect the mean temperature on Earth would be -18°C and there would be very little or no life. So the greenhouse effect itself is a good thing.

Global warming

Global warming is the increase in the mean temperature of the Earth. The ten hottest years since records began have been in the last 30 years. The mean increase in the last 100 years has been less than 1°C. This might seem small, but is enough to have devastating consequences on many species in different parts of the world.

Global warming graph showing the percentage of CO2 in the atmosphere since 1700. It remains steady at 0.028 per cent until approx 1850 and then starts rising steeply reaching 0.035 per cent by 2000.Graph showing change in global temperature over 100 year period

As the percentage of carbon dioxide in our atmosphere has increased so has the Earth's mean temperature. Note that the shape of the first graph showing the amount of carbon dioxide in the atmosphere is exponential and is a similar shape to graphs showing human population change over the same time period. When comparing graphs such as changes to carbon dioxide levels and temperature against time, note that the axes are drawn to different scales, and do not start at '0'.

The consequences of global warming are:

  • melting of the polar ice caps
  • the rise in sea level may one day threaten many cities such as London, New York and Amsterdam
  • weather patterns will change with more unusual weather
  • animals will migrate towards the poles to find habitats with suitable temperatures
  • tropical diseases may become more common in other regions, such as Europe
  • change in distribution of pests that attack crops, which will have an impact on food security in some areas
  • many species will become extinct
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