This chapter provides a geophysiological perspective on climate change, both in Earth history, and in future. Ozone in the unpolluted atmosphere is affected in the stratosphere by the biological production of chlorine and bromine-containing gases and nitrous oxide, and in the troposphere by the emission of terpenes and other hydrocarbons by vegetation. The response of the atmospheric water cycle to global warming is complex, and no credible prediction of future climate is possible without an account of the redistribution of water in the environment. Biological systems are known to affect the state and abundance of water in the atmosphere. Over land evapo-transpiration affects the water cycle on both local and regional scales. The gaseous greenhouse is a property of the geo-physiological system, not just a part of an inert environment to which organisms merely adapt. Where there is feedback from climate change on the rate of biogenic or biologically mediated removal or production of greenhouse gases, a coupled feedback system exists that inextricably links the evolution of organisms and climate.