Are observed climate variations best described as cyclical, stochastic, or chaotic in nature? This is the essential question posed by W.J. Burroughs. Our confidence in climate predictions on time scales of seasons to centuries, including the global warming debate, depends on the answer. The book explores evidence and arguments for cyclical features in direct meteorological records such as temperature and precipitation, as well as indirect, or proxy, climate data derived from geological, biological, and economic data series. It then proceeds to lay out the physical and statistical mechanisms that may support the existence of these cyclicities when the observations are messy, indirect, incomplete, or simply don’t span enough time.