60 second guide to... Transport emissions
Planes, trains and cars all contribute to the growing concentration of climate change gases. But how do they compare and which one pollutes the most?
How green is our transport?
The overwhelming majority of the world's vehicles are powered by oil, either in the form of petrol (most cars), diesel (most trucks) or kerosene (most planes). Even those trains and cars powered by electricity usually rely on fossil fuels being burned in power stations.
All told, transport accounts for around 14 per cent of human-created greenhouse emissions – and that’s excluding the manufacture of vehicles. Most transport emissions take the form of CO2, created when carbon in the fuel is burned in an engine and combines with oxygen in the air.
Gas guzzlers
Comparing the emissions of various modes of transport is tricky, since there are so many variables to consider. For example, some trains run on electricity while others run on diesel. Some cars are fuel efficient while others are gas guzzlers. Similarly, short flights are more polluting per mile than long ones (since take-off accounts for a larger amount of fuel use), but less polluting overall.
There’s also the question of how to factor in the occupancy rates of the vehicles. Driving a car containing four people saves more energy per passenger than solo driving. But taking an extra passenger doesn’t actually reduce the total impact of the trip. If anything, it increases it, due to the extra weight being carried.
With these caveats in mind, it is possible to calculate typical figures for per passenger emissions of various forms of transport. The figures for flights are multiplied by three to account for the non-CO2 greenhouse impacts of planes.
Added pollution
Aside from climate change, motor vehicles also emit
particles and gases (such as sulphur dioxide and carbon monoxide) that can be
harmful to human health. Things have improved thanks to catalytic converters
and unleaded petrol, but the problem is still very real.
The World Health Organisation estimates that around 800,000
people a year die prematurely due to air pollution, most of it related to
vehicles. Even in the UK, the figure is more than 30,000.
Diesel vehicles tend to be better than petrol vehicles in
terms of greenhouse emissions, but worse in terms of local air pollution. Against
this backdrop, it is hardly surprising that engine manufacturers across the
world are increasingly focusing their attention on developing cleaner
technologies.
It’s all about distance
The total climate impact of a trip depends not just on the emissions per passenger kilometre, but also on the distance travelled. This is why flying can add so much to a person’s carbon footprint. Planes let us travel vast distances in just a few hours – something that simply isn’t possible any other way.
A single long haul flight, eg London to Cape Town, can cause the equivalent of more than 3 tonnes of CO2 emissions. This is around the same as the average UK car owner clocks up in a year of driving.
Team Green Britain and London Organising Committee of the Olympic Games and Paralympic Games Ltd (LOCOG) do not endorse any of the products, companies, organisations, opinions or websites that have been mentioned in this article. The content of this article has merely been provided as background to, or discussion on, various topical issues relating to the environment and it is not necessarily representative of the views of Team Green Britain and LOCOG. Further, any figures and calculations noted in this article are estimates (unless otherwise specified), and may vary in light of numerous factors and readers are advised to undertake their own research in relation to the facts and figures applicable to their particular circumstance.