Over the last few decades, there has been growing concern over the international security implications of large-scale environmental problems, including those associated with the production and use of energy resources. Recently, this attention has focused on the possibility of major climatic changes caused by growing atmospheric concentrations of carbon dioxide and other trace gases that result, primarily from our combustion of fossil fuels. Given the extent and severity of the likely climatic changes, it is increasingly urgent that we begin to ask how climate changes will affect international relationships, economics, access to resources, and national security.