What is climate change? The definition, causes and effects

Here’s what we know and don’t know about our planet’s changing climate.

What is climate change?

The planet’s climate has constantly been changing over time.

The Earth’s average temperature is about 15C, but some evidence suggests it has fluctuated between much higher and much lower in the past.

However, the current period of warming is occurring more rapidly than many past events.

Climate scientists are concerned that the natural fluctuation is being overtaken by a huge human-induced warming that has serious consequences for the stability of the planet’s climate.

What causes it?

A natural function of the Earth’s atmosphere is to keep in some of the heat that is lost from the Earth. This is known as the greenhouse effect.

The atmosphere allows the heat from the Sun (short-wave radiation) to pass through to heat the Earth’s surface.

The Earth’s surface then gives off heat (long-wave radiation).

This heat is trapped by greenhouse gases (eg methane, carbon dioxide and nitrous oxide), which radiate the heat back towards Earth.


This process heats up the Earth.

Some human activities increase the greenhouse gases in the atmosphere:

  • Burning fossil fuels, eg coal, gas and oil – these release carbon dioxide into the atmosphere.
  • Deforestation – trees absorb carbon dioxide during photosynthesis. If they are cut down, there will be higher amounts of carbon dioxide in the atmosphere.
  • Dumping waste in landfill – when the waste decomposes it produces methane.
  • Agriculture – agricultural practices lead to the release of nitrogen oxides into the atmosphere.

There are also natural factors which contribute to increased global warming:

  • Orbital changes – the Earth has natural warming and cooling periods caused by Milankovitch cycles or variations in the tilt and/or orbit of the Earth around the Sun (Wobble, roll and stretch theory).
  • Volcanic activity – during a volcanic eruption carbon dioxide is released into the atmosphere.
  • Solar output – there can be fluctuations in the amount of radiation from the sun. If there is high amount emitted there will be an increase in Earth’s temperatures.

What are the effects of climate change?

Global warming can have negative impacts on the world.

Negative impacts of global warming around the world include: sea levels rising that will affect 80 million people; tropical storms will increase in magnitude (strength); species in affected areas (eg Arctic) may become extinct; diseases such as malaria increase, an additional 280 million people may be affected.

But there might also be some positive impacts of a warmer climate around the world including: energy consumption may decrease due to a warmer climate; longer growing season for agriculture; frozen regions such as Canada may be able to grow crops.

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