With new sources and methods of global petroleum production coming on stream — shale fracking, ultra-deepwater drilling and new fields in Africa, to name a few — some energy analysts have argued that reports of the death of cheap oil have been greatly exaggerated. In this week's CIGI Interview, Thomas Homer-Dixon takes issue with these "oil optimists," saying that the petroleum our global economy can afford to consume is indeed running out, and that we need to be much more aggressive in developing alternative energy sources.