The following exchange was the result of ongoing informal conversations among the contributors, who are all, in different ways, interested in the emergent concept of the Anthropocene and the challenges it posed, and the opportunities it provided, for historians working on Britain and the world. The conversation began at the end of 2015 and continued for about a year.

According to the United Nations University Institute for the Advanced Study of Sustainability, ‘cities are responsible for 67% of the total global energy consumption and more than 70% of greenhouse gas emissions and these trends significantly intensify the severity of some of the two great challenges of our time; climate change and energy security’. Moreover, if cities are driving anthropogenic climate change, the effects are felt everywhere on earth, from glaciers to atolls, from oceans to the troposphere. It is no longer simply society that has been, to cite Henri Lefebvre, ‘completely urbanized’. The entire planet and its atmosphere have been subordinated to the metabolic demands of extremely large human settlements.