The wide range of data that can be exploited in the search for weather cycles must now be put in context. This database provides a considerable amount of information about the scale and time-span of a variety of meteorological variables. But to understand what insight, if any, these observed fluctuations provide about the overall cyclic behaviour of the weather, we need to look more closely at how the global climate functions. For only when the variability of the weather is analysed in terms of the processes that govern the global and regional energy balance of the Earth's climate is it possible to make a sensible assessment of the evidence of cycles. In particular, the possibility that all the ups and downs in the weather are nothing more than the natural variability of the complex non-linear connections between various components of the climate must be explored in detail. Once this issue has been examined it will be possible to focus on the more precise question of cyclic behaviour.

This approach cannot go over all the standard climatological ground covered by text books (see the bibliography). Instead, it will concentrate on those features of the global climate that are apparently most closely linked with the fluctuations identified in Chapters 3 and 4.