Chapter 3 has reviewed the various methods and techniques used both to construct contemporary climate from instrumental records, and to reconstruct palaeoclimates from proxy data sources. Whenever an indicator, whether instrumental or proxy, is chosen to represent some aspect of the climate, one must be sure that there exists a physical basis for the choice of that indicator i.e. variations in the record of that indicator truly reflect variations in that aspect of the climate one is attempting to measure.
In all climatic and palaeoclimatic analyses, it should be the aim of the investigator to maximise the (climate) signal to (non-climatic) noise ratio, without compromising the validity of the data.
In chapter 5 the use of the proxy methods for palaeoclimate reconstruction across geologic time are discussed. Particular attention is paid to the climates and climate changes of the Quaternary. First, however, chapter 4 investigates another tool used to assist the scientist in understanding climate change: climate modelling.