As part of your study of GCSE physical geography, you will look at climate and climate change. Climate change is the result of natural and human factors, and has a range of effects. Since the late twentieth century, much of the talk of climate change has been about the greenhouse effect and global warming.
Global warming is the result of the greenhouse effect. The greenhouse effect is created by greenhouse gases such as carbon dioxide, methane and even water vapour in the atmosphere. During the day, the surface of the Earth is warmed by the Sun's rays. At night, this heat is lost into space. Greenhouse gases reduce this heat loss and without them, the Earth would have an average temperature well below zero Celsius. There would be no liquid water at the surface, making things extremely difficult for life.
If the quantity of greenhouse gases in the air is too high, the balance between heat input and heat lost is disturbed and the average temperature rises.