5.1 Climate models
The answer is that scientists use models to estimate to what extent each suspect and red herring affects the climate. A model is simply something that represents something else.
Climate models are mathematical equations that represent part, or all, of the Earth system. Most climate models are extremely complex, with many thousands of equations. These are too complicated for humans to calculate, so they are calculated by computers.
You will study these complex climate models more later. For now, it is enough to say that these state-of-the-art computer models are designed to represent, or simulate, all important aspects of the climate system. Climate models enable climate scientists to assess how the Earth system responds to different factors. They provide us with a means of carrying out virtual experiments on the climate system: by changing the various inputs, we can simulate a wide range of possibilities.