This report investigates the effects of an increased exploitation of shale gas reserves around the globe and the extent to which it can serve as a low-cost GHG mitigation option. We compare a scenario of global shale gas exploitation with a scenario in which shale gas use is very limited. Both scenarios are modelled with the global techno-economic POLES model and rely on a high regional disaggrega-tion. The effects of shale gas production on the energy market and, consequently, on GHG emissions are analysed in a baseline case without additional climate policy and for mitigation targets compati-ble with the 2°C target. We find that shale gas should not be considered a cheap option to reduce global GHG emissions due to three reasons: the effects of global shale gas availability (a) are small in the short-term, (b) lead to higher baseline GHG emissions for most countries in the long-term due to lower energy prices and (c) result in higher costs of compliance with climate targets.