Question to the Department for Transport:

To ask the Secretary of State for Transport, for what reasons his Department ceased to use a multiplier of 1.9 for the radiative forcing or non-CO2 effects of air travel in 2011 for Departmental passenger demand and CO2 forecasts; and if he will make a statement.

The Department does not quantify the non-CO₂ impacts of aviation because of the extent of the scientific uncertainty in this area. Whilst there are a number of emission types from air travel, other than CO₂ that are known to have an impact on global warming, the magnitude of these impacts is not well known. This approach is consistent with the Committee on Climate Change’s recent advice that acknowledges the difficulties in measuring and reporting the impact of non-CO₂ emissions.