London's daily greenhouse gas emissions. Artwork illustrating of the daily greenhouse gas emissions of greater London. Every day greater London emits 139 thousand tonnes of greenhouse gases. This would fill a sphere (blue) with a diameter of 521 metres. This volume is shown on the same scale as some of London's best known landmarks. These are, from left to right: 1 Canada Square (Canary Wharf Tower), Post Office Tower (BT Tower), Tower 42 (NatWest Tower),St Stephen's Tower, 30 St Mary Axe (The Gherkin), Tower Bridge, London Eye and The O2 Arena (formerly the Millennium Dome). The emission of greenhouse gases, such as carbon dioxide, contributes to global warming.