This response addresses the first two questions of the call for evidence on the impact of shale gas on energy markets: firstly what estimates exist for the amount of shale gas in place in the UK, Europe, and the rest of the world, and what proportion is recoverable; and secondly why estimates for shale gas are so changeable. UKERC recently conducted a comprehensive review of 62 studies that provide original estimates of regional and global shale gas resources [1 |