The recent ‘shale gas revolution’ in the United States has created huge uncertainties for international gas markets that are likely to inhibit investment in gas – both conven- tional and unconventional – and in many renewables. If the revolution continues in the US and extends to the rest of the world, energy consumers can anticipate a future dominated by cheap gas. However, if it falters and the current hype about shale gas proves an illusion, the world will face serious gas shortages in the medium term.