The Hot Car Effect
On a warm sunny day you come back to your locked up car. What is it like inside the car? It is boiling hot — much hotter than outside. Why is that?
This is the greenhouse effect. The energy from the sunlight can go through the glass of the window, but some of the heat is trapped inside the car. As this continues to happen the car becomes very hot inside.
The Greenhouse
This is the same thing that happens with a greenhouse (or glasshouse). People in cooler places have used greenhouses for centuries to grow plants that need a warmer climate. Sunlight can go through the glass or plastic but then the heat gets trapped inside.
The Earth as a Greenhouse
The Earth can also be considered a bit like a greenhouse. Instead of glass around the outside, we have the atmosphere. This is all the gases that make up our air. The atmosphere surrounds the Earth. There are gases in the atmosphere such as carbon dioxide (or CO2) that act like the glass in the greenhouse — they trap the heat. See the picture below.
As the world continues to pollute and damage the environment, there are more and more greenhouse gases being put into the air. This makes the atmosphere trap more and more heat. So the Earth starts to warm up.
The use of energy such as petrol in cars and electricity from coal power stations makes more greenhouse gases. This is why many people believe that we have to re-think our use of energy.