1. a School of the Built Environment, Heriot Watt University , Edinburgh, EH14 4AS, UK
2. b Faculty of Architecture, Design and Planning, Wilkinson Building G04 , University of Sydney , NSW, 2006, Australia
3. c Association for the Study of Peak Oil and Gas , Staball Hill, Ballydehob Co., Cork, Ireland
4. d School of GeoSciences, University of Edinburgh , Edinburgh, EH9 3JW, UK