4.2.1 Deciding what action to take
Although there are uncertainties involved in calculating the effects of different actions on your carbon footprint, some information is readily available. For example, you can check the CO2 emissions per kilometre of different car models on government websites (VCA, 2016). But emissions from air travel depend on whether the additional radiative forcing effect on the upper atmosphere of the nitrogen oxides and water vapour in aircraft emissions is counted. Based on current science, the UK Government recommends multiplying CO2 emissions from flights by 1.9 then adding the CO2 equivalent emissions of other GHGs. This has been done for the flight emissions in Table 5b and also in the carbon calculator (DEFRA, 2015).
The CO2e savings from changing diets or recycling materials are also difficult to calculate. Many of the figures quoted depend on life-cycle analysis, the results of which vary widely. For example, while cows and sheep produce large amounts of the powerful greenhouse gas methane when digesting their food, the effects of reducing meat and dairy consumption depend on what is substituted. If out-of-season, imported vegetables and rice are substituted, the footprint could be greater than for a diet with small amounts of locally produced beef and lamb fed on grass rather than imported grains.
Buying locally produced food can help to reduce emissions and food miles, especially if the food is imported by air. However, for most foods the main impacts arise from production and processing, and reducing food miles may not be the best option. For example, imported tomatoes grown outdoors in Spain have a lower carbon footprint than tomatoes grown in a heated greenhouse in the UK.
Table 5a–d showed the impacts of selected actions in terms of ‘ballpark’ GHG emissions. But other environmental impacts may be as, or more, important. A dramatic example was the scandal in 2015 when a major car manufacturer was shown to be concealing the amounts of unhealthy NOX air pollution from its diesel cars, which previously had been considered ‘greener’ due to their lower CO2 emissions than petrol cars (Porter, 2016).
There are many other cases where choosing between alternative environmental actions involves trade-offs and compromises. For instance, chickens reared indoors in cramped conditions are more efficient at converting their feed to meat than free-range birds. Intensively reared chicken therefore has a lower carbon footprint than free range, but at the cost of poorer animal welfare. While the carbon savings from avoiding plastic carrier bags may be negligible, the 150 million tonnes of plastic waste (mostly packaging) now in the oceans has become a major threat to marine life (World Economic Forum, 2016), a more important reason for reducing plastic waste.
Remember from Section 2 that household income and size also have a very big effect on individual carbon footprints. There may be little you can, or want to, do about your income, but you may have some control over how you spend it; for example, you could spend spare income on insulating your home, on holiday flights, or on ‘offsetting’ your emissions (see Section 5). The number of people in your household may also not be something you can change, but if you have spare room it is usually carbon efficient to occupy it.
That raises the highly sensitive issue of children. Having a child probably adds more to your carbon footprint than any other decision you might make (even if the child increases your household’s size). Berners-Lee (2010, p. 151) has calculated that the mean footprint of an extra child born in the UK is about 373 tonnes CO2e over an average 79-year life. And that doesn’t take into account the fact that the child is likely to have children too. One estimate of the total effect of each extra female child born in the USA, including their offspring, is nearly 9500 tonnes CO2 (Murtaugh and Schlax, 2009).