Imma Perfetto
Cosmos science journalist
Researchers have raised the prospect that aviation emissions should be included national statistics of carbon use – at the moment they are omitted by nearly all countries.
A new study in Nature Energy suggests limiting long distance travel – rather than local and commuter journeys – may be more effective at reducing passenger travel carbon emissions.
Researchers from the University of Leeds say trips of more than 80km (50 miles) one way are responsible for 70% of all passenger travel-related carbon emissions, despite accounting for less than 3% of all trips by UK residents.
International journeys, which are only 0.4% of total trips taken, account for 55% of emissions.
“Whilst efforts to move local journeys to more sustainable modes of transport are really positive, by omitting aviation emissions from national statistics – as is the case at the moment in nearly all countries – we are not getting a holistic picture and ignoring a large part of the problem,” says co-author Muhammad Adeel, a researcher at the Centre for Transport and Society at the University of the West of England.
To calculate which types of travel could be changed to maximise a reduction in carbon emissions while also impacting as few people or trips as possible, they created a new metric – emission reduction sensitivity – calculated by dividing the carbon reduction percentage by the percentage of journeys altered.
Using UK data from the National Travel Survey and the International Passenger Survey, they found that if car journeys under about 13km (8 miles) were shifted to walking or cycling, it would result in a 9.3% reduction in carbon emissions.
However, as these types of journeys make up most travel (55%) the emission reduction sensitivity of doing so would be just 0.17 – the lowest in the study.
In contrast, if all flights of less than 1600km (1,000 miles) were moved to rail, there would be a 5.6% reduction in emissions affecting only 0.17% of all journeys. This change would have an emission reduction sensitivity of 33.2.
At the most extreme end of the scale, limiting everyone who flies to one return flight abroad per year would have an emission reduction value of 158.3.
The researchers hope that their findings will drive policymakers to look at how effort is assigned when dealing with the impact of travel on the environment.
“The important thing both at the policy and personal level is that we prioritise the relatively fewer longer distance trips – especially flights – in order to realise the largest reductions,” says Zia Wadud from the University of Leeds Institute for Transport Studies and School of Chemical and Process Engineering, who led the research.
