Although road transport is not the highest emitter of greenhouse gases, it exhibits 50% of the net radiative forcing from all industrial sectors* since nearly all the emissions it produces lead to net positive forcing. Conversely other significant emitters of greenhouse gases such as the power and industry sectors also produce significant amounts of sulphates which cool the atmosphere. This unintentionally helps to mitigate the warming effect of their greenhouse gases. However, sulphates are serious pollutants in their own right and these will be reduced further in the future causing these sectors to make greater contributions to net global warming. Therefore, on a sector by sector basis, it is suggested that reducing or limiting road transport would be an effective short term global warming mitigation strategy, whilst limiting emissions from sectors such as power generation and industry will become more important over the longer term.
Household biofuel exhibits 33% of net radiative forcing over the short term, this is partly due to its black carbon emissions which unlike carbon dioxide has a relatively short residence time in the atmosphere. Black carbon is also emitted by the Diesel component of road transport. Therefore, on a pollutant by pollutant basis, the reduction of black carbon would be a highly effective short term global warming mitigation strategy.
Influence of different sectors on radiative forcing in 2020
* The 50% is calculated by adding the forcing's on the left (398) and divide this into the on-road component (199)