In response to increasing academic interest, Cambridge University Press launched a new journal in 2006, entitled the Journal of Global History. To inaugurate the endeavour, the editors asked economic historian Patrick O'Brien to write an introductory essay to serve as a prolegomenon for this newly invigorated field of study. O'Brien began by noting that it is no mere coincidence that interest in global history should be growing, given the global challenges entailed in current-day economic, political and environmental issues. From this perspective, we might take “global history” to refer both to the field's geographical reach and its attempts to relate a global range of seemingly diverse phenomena. Both understandings require us to stretch beyond the narrow specialisms in which we were trained and invite increasing willingness to collaborate. Along these lines, O'Brien applauded those historians who have reached outside their own discipline to draw on the insights and methods of the natural sciences, as well as natural scientists whose work is shedding new light on historical development.