“Climate is a rather elusive entity,” wrote Helmut Landsberg in 1950 as he sorted out some twenty or so competing definitions. This volume of Osiris explores the complexities in understanding what climate means from a historical perspective. The title of this volume, Klima, evokes its Greek origins, κλίμα, meaning an extended period encompassing vast layers of different kinds of meteorological information. The volume thus seeks not only to decouple Klima from its current exclusive association with atmospheric sciences, but also to re-visit the implications of an ancient vocabulary for medical, geographical, agricultural, economic, racial, and other “endemic” concerns. If climate is not just about the weather, what is it? The essays in this volume treat climate discourse as a framing device that makes explicit all social concerns arising from the anxiety over the sensible and latent experiences of living in an atmosphere of hunger and satiation, disease and health, poverty and wealth, isolation and community, angst and hope. James Fleming is a historian of science and technology and Professor of Science, Technology and Society at Colby College, Maine. Vladimir Jankovic is a faculty member, at the Centre for the History of Science, Technology and Medicine, University of Manchester. He is a historian of atmospheric sciences, and has published in the history of meteorology, geography of environmental knowledge, and medical climatology.