When Ihe public, media and politicians talk aboul climate change, they mostly have in mind changes in weather patterns, impacts on agricultural production and disruptions in supporting energy systems. Yet climate change will affect, and in some cases already is affecting. the dynamics of all components of the earth's system. Climate change is not an isolated phenomenon, but just one dimension of an increasingly evident human imprint on the earth at a global level, which affects climate, land use. resource exploitation and pollution, among other issues. Many of these issues are linked through positive feedbacks that increase their impacts. Therefore, we often refer to "global change" rather than "climate change", in acknowledgement of the links between the physical, chemical and biological systems that regulate the earth and the social systems that it supports.