The greenhouse effect
The Earth’s atmosphere develops a natural greenhouse effect, and it is this that keeps the planet warm and a safe place for us to live. The greenhouse gases in the atmosphere (water vapour, carbon dioxide, nitrous oxide and methane, for example) trap energy from the sun near the surface of the Earth. Without these gases, heat would escape back into space and the Earth would be a much colder place. If the balance of greenhouse gases is altered then it has a big impact on life on Earth. The way we have lived since the Industrial Revolution has increased the amount of carbon dioxide in the atmosphere and this is causing the climate to change.
Scientists have been thinking about how the emissions of gases affect the climate from as early as the 1800s. Much of the pressure on politicians to do something about climate change now actually comes from the scientists who can see serious changes ahead for our climate. In 1988, the Intergovernmental Panel on Climate Change was formed by the United Nations to look at the best available information on climate change from all over the world. The latest report warned that average global temperatures could increase by up to 5.8°C by the end of this century.
How does the greenhouse effect work?
The geenhouse effect is a fairly simple process. The above diagram explains the geenhouse effect, which is at the heart of climate change.
- Heat from the sun, in the form of radiation, penetrates the atmosphere. This causes the Earth to warm up.
- Some of this heat is reflected back into space off clouds.
- Some of the heat is reflected back into space off the surface of the Earth.
- Some of the heat is trapped near the surface of the Earth by the planet's natural greenhouse effect.
- As the Earth warms up some heat is lost back into space through the atmosphere.
- Increasing the amount of greenhouse gases in the atmosphere means the heat from the Earth cannot escape into space so the Earth continues to heat up.
Carbon dioxide is the biggest problem as far as greenhouse gases are concerned. It is produced through the burning of fossil fuels (coal, gas and oil) and the rotting of green waste (trees and plants). The build-up of carbon dioxide in the atmosphere stops the heat from the sun being reflected back into space and traps it on the surface of the Earth. As the build-up of carbon dioxide increases, the heating increases and the global surface temperature rises. The atmosphere acts like the glass in a greenhouse, so the more carbon dioxide we put in the atmosphere, the hotter it becomes. Higher temperatures cause more storms, rising sea levels and changing weather patterns.
These changes create further changes that affect the climate in the longer term. Reducing the amount of carbon dioxide we release into the atmosphere will return the greenhouse effect to more stable levels and help reduce the impact of climate change.
We also need to look at the balance of gases in our atmosphere which are changed when we cut down forests and replace them with agricultural land. Trees add oxygen back into the atmosphere whereas agricultural land increases methane amounts (from animals) for example.
How do you measure carbon dioxide?
Carbon Dioxide (also called CO2) is often mentioned when talking about climate change. Often scientists refer to planes and cars producing so much CO2. But it is difficult to understand what these figures mean.
An organisation called Best Foot Forward has come up with a simple way of getting us to understand what a certain amount of CO2 can look like.
Access the Best Foot Forward Ltd website (link opens in a new window)
If you picture a party balloon – one of these holds 10grams (1/3oz) of CO2. A hundred party balloons will hold 1kilogram (2.2lb) of CO2 and a hot air balloon will hold 1,800 kilogrammes (1.8tonnes) of CO2.
Driving from Hull to Leeds and back, which is a distance of 102 miles, on average will produce 32 kilogrammes (70.4lbs) of CO2 from the petrol.