Causes of global warming

Physical and human

Temperature variations are caused by a combination of physical and human factors.

Causes of climate change

Physical causes

Physical causes of global warming and cooling include:

  • Variations in the sun's energy - sunspot activity raises global temperature.
  • Volcanic eruptions, large quantities of volcanic dust in the atmosphere shields the Earth from incoming heat, (exposure to the Sun's rays), lowering global temperature.

Powerful volcanic eruptions

  • Changing oceanic circulation such as the periodic warming and cooling of areas of the tropical Pacific Ocean.
  • Melting permafrost in cold deserts releases large quantities of methane gas.

These physical causes of global temperature change have always existed and have been responsible for the alternating heating and cooling cycles of the Earth's temperature.

Human Causes

Cars in China battling through choking pollution
Cars in China battling through choking pollution

The human causes of global warming have been in the news a lot in recent years, you can probably think of a few examples. Human factors are the result of growing population and economic developments.

They include:

  • The burning of fossil fuels for transport, industry and power, producing carbon dioxide.
  • Worldwide deforestation, sometimes involving rainforest burning, which also produces carbon dioxide.
  • Car exhausts, nitrogen fertilisers and power stations producing nitrous oxide.
  • CFCs found in fridges, air conditioning and aerosols.
  • Methane produced from rice fields, landfill sites and from both ends of cattle.

The main greenhouse gases in the atmosphere are carbon dioxide, methane and nitrous oxide. They are naturally occurring in the atmosphere, but are believed to have increased through burning more oil, petrol, and coal, while forests have been removed.

Carbon dioxide, methane and nitrous oxide have caused an enhanced greenhouse effect. The build-up of greenhouse gases such as carbon dioxide (CO2) in the atmosphere, is believed to result in more heat being retained in the atmosphere than would usually be the case. Naturally, more of the heat from the Sun would be reflected back into space.

Collectively, these physical and human causes have produced the pattern seen in the graph above.