What causes climate change?
The atmosphere traps some of the heat that is reflected from the Earth’s surface. This is known as the greenhouse effect. Without this natural process, temperatures would be much colder on Earth. 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 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 the natural greenhouse gases, such as carbon dioxide, methane and nitrous oxide.
which radiate the heat back towards Earth. This heats up the Earth.
The Greenhouse Effect
Human factors increasing global warming
Human activities increase the volume of greenhouse gasses in the atmosphere. This leads to global warming because the gasses trap more of the infrared heat reflected by the surface of the Earth.
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 an increase in the atmosphere.
- Burning fossil fuels – when coal, oil and gas are burned they release carbon dioxide into the atmosphere.
Emissions from a coal power plant
- Agriculture – an increase in pastoral (animal) farming leads to more methane being released into the atmosphere
- Dumping waste in a landfill – as waste decomposes in a landfill it releases methane
- Agriculture – agricultural practices lead to the release of nitrogen oxides into the atmosphere.
Natural factors increasing global warming
As well as human activities, natural processes contribute to global warming. These are:
- Orbital changes – Milankovitch cycles, which are variations in the tilt/orbit of the Earth around the sun causing natural periods of warming and cooling.
- 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.