Shale gas, where it displaces coal in the electricity generation mix, presents a substantial reduction in CO2 emissions. These two images highlight the state of affairs in terms of global CO2 budgets. The first image shows CO2 emissions from fuel source and from country (in 2008). Clearly, Chinese and American coal are by far the biggest culprits. The second shows an estimate of the amount of CO2 embedded in fossil fuels as yet unburned. This presents us with a clear choice - if we are to continue burning fossil fuels, we should be choosing to burn gas.