What causes climate change?

The atmosphere traps some of the heat reflected from the Earth’s surface. This natural process is known as the greenhouse effect. Without this natural process, temperatures would be much colder on Earth. For example, without naturally occurring greenhouse gases, Earth’s average temperature would be near -18°C instead of the much warmer 15°C.

The greenhouse effect works by the atmosphere allowing heat from the Sun (short-wave infrared radiation) to pass through to heat the Earth’s surface. The surface of the heat then gives off heat as longwave radiation. Some of this heat is trapped by natural greenhouse gases, such as carbon dioxide, methane and nitrous oxide, radiating the heat back towards Earth, heating the Earth.

The Greenhouse Effect

Human factors enhancing the greenhouse effect

Human activities increase the volume of greenhouse gasses in the atmosphere leading to the enhanced greenhouse effect because increased greenhouse gases trap more of the infrared heat reflected by the surface of the Earth. Average global temperature increases due to this.

Enhanced Greenhouse Effect

Human activities that lead to an increase in greenhouse gases in the atmosphere include:

• Deforestation (cutting down trees) – trees absorb carbon dioxide during photosynthesis. When trees are cut down, less carbon dioxide will be absorbed, leading to increased concentrations in the atmosphere.
• Burning fossil fuels – when coal, oil and gas are burned, carbon dioxide is released into the atmosphere.
  

  Emissions from a coal power plant

• Agriculture – Increased pastoral (animal) farming leads to more methane being released into the atmosphere.
• Dumping waste in a landfill – as waste decomposes, it releases methane.
• Agriculture – agricultural practices lead to releasing nitrogen oxides into the atmosphere.

Natural factors enhancing the greenhouse effect

As well as human activities, natural processes contribute to the enhanced greenhouse effect. These are:

• Orbital changes – Milankovitch cycles are variations in the tilt/orbit of the Earth around the Sun, causing natural warming and cooling periods.
• Volcanic eruptions – carbon dioxide is released into the atmosphere during eruptions.
• Solar output – the amount of radiation emitted by the Sun fluctuates. High levels of radiation lead to an increase in Earth’s temperatures.

Next: What are the effects of climate change?