Introduction to climate change
Learn about climate change including the causes of global warming.
This lesson includes:
two videos explaining and providing evidence for climate change
Watch this video to find out why there has been a dramatic increase in global temperatures since 1950 and how it is affecting the Earth.
The global climate has been changing since time began and will continue to change into the future.
The Earth's temperature has fluctuated in the last few hundred years.
However, since around 1950 there has been a dramatic increase in global temperatures.
This increase is known as global warming.
Evidence for global warming
- Thermometer readings - By using data from ongoing temperature readings scientists have seen an average combined land and ocean surface temperature increase of 0.85°C since the end of the 19th century.
- Glacier retreat - the increase in global temperatures is causing glaciers to disappear and is increasing the melting of sea ice in the Arctic.
- Ice cores - Scientists that study the ice cores say there is clear evidence that there has been a rapid increase in temperature in the past decades.
- Early spring - In recent years there have been signs of a seasonal shift - spring arrives earlier and winters tend to be less severe.
- Rising sea levels - Between 1901 and 2010, average global sea level rose by 0.19 m.
Causes of climate change
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 retention of heat in the atmosphere caused by the build-up of greenhouse gases).
- 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 (gases responsible for global warming eg methane, carbon dioxide and nitrous oxide), which radiate the heat back towards Earth.
- This process heats up the Earth.
Human factors increasing global warming
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.
Natural factors increasing global warming
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 (a theory that describes the effects of the Earth's movements on its climate) 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.
Watch this short film with Countryfile presenter Tom Heap discussing the idea that the UK climate might be changing, with increased droughts, increased summer temperatures but wetter winters.
Here are a few activities to try to help you remember what you've learnt about climate change.
Rank the evidence
After watching the above video, rank the reliability of each data source and decide which is the strongest evidence for climate change in the UK.
There's more to learn
Have a look at these other resources around the BBC and the web.