We have seen global temperature rise over the 20th century by around 0.7 °C. Climate scientists don’t have a ‘climate in a test tube’ to try out their ideas, so to understand the climate and why it changes, they create computer models that they use to do ‘experiments’. This booklet provides an introduction to the way in which the climate can be modelled and the science behind the models. The activities include practical experiments, simple examples of climate modelling, and analysis of observed data. They are intended primarily for KS4 students, but could also be used for post-16 students.