Causes of Global Warming

  1. The scientific consensus is that the recent increase in global temperature is caused by human activity.
  2. Human activity has caused global warming by enhancing the greenhouse effect - the effect of greenhouse gases absorbing outgoing energy, so that less is lost to space.
  3. The greenhouse effect is essential to keep the planet warm, but too much greenhouse gas in the atmosphere means the planet warms up.
  4. Two of the main green house gases are CO2 and methane:
  • Atmospheric CO2 concentration has incresed rapidly since the mid-19th century from 280 ppm to nearly 380ppm. The concentration had been stable for the previous 10 000 years.
  • CO2 concentration is increasing as more fossil fuels like coal, oil, natural gas and petrol are burnt. Burning fossil fuels releases CO2.
  • CO2 concentration is also increased by the destruction of natural sinks. CO2 is released when trees are burnt, or when decomposers break down the organic compounds and respire them.
  • Atmospheric methane concentration has increased rapidly since the mid-19th century from 700ppb to 1700ppb in 2000. The level had been stable for the previous 850 years.
  • Methane concentration is increasing because more methane is being released into the atmosphere, e.g. more fossil fuels…


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