02Why cities will need to play a central role in the net zero agenda
The UK needs to make progress on transport and domestic emissions to meet its net zero goals
The UK has made considerable progress in cutting its emissions since the turn of the century. Greenhouse gas emissions have already halved compared with 1990 levels (Figure 1).2
Figure 1: UK greenhouse gas emissions have halved since 1990
Over the past three decades, the main driver has been a reduction in industrial and commercial emissions (Figure 1). The phasing out of coal, gradual uptake of renewable energy and structural shift away from carbon-intensive manufacturing account for nearly 70 per cent of the progress made in the past 20 years. However, much less progress has been made in transport and the domestic sector, which now account for more than 64 per cent of all carbon emissions (Figure 1). Transport emissions have fallen by just 3 per cent since 1990, while those from the residential sector have decreased by only 13 per cent, and have remained largely flat since 2013.
The next half of the challenge is likely to be more difficult. Relying on improvements in the industrial and energy supply sector alone will not be enough: the share of coal in the ‘electricity mix’ is now very limited, so the marginal room for improvement is smaller.3 Government projections show that if no additional measures are taken, emissions are likely to flatten out (Figure 1). If the UK wants to meet the net zero target by 2050, the pace of change needs to accelerate in other sectors like transport and housing. And on these two counts, cities and large towns have a particular role to play.
Further reductions in transport and domestic emissions will be more easily delivered in cities
Reducing emissions from transport and domestic heating will require a change in the way people go about their daily lives. Their ability to do this will be influenced by the built environment.
Despite perceptions that cities are bad for the environment, the opposite is true when considering climate change. The 63 largest cities and towns in the UK generate 45 per cent of all emissions, with London accounting for 10 per cent. But cities and large towns are home to 54 per cent of the population, so emissions per capita are much lower than in more rural areas, and the average Londoner produces less carbon than someone living outside a city or large town. On average, cities and large towns produce about four tonnes of CO2 per capita, compared with more than six tonnes elsewhere in the UK (see Figure 2). Only four have per capita emissions above the non-urban average.
There are two reasons for this. Firstly, with the exception of a few , high-emitting industrial activities tend to be located outside of cities, and this is likely to continue as they increasingly specialise in knowledge-intensive industries. Secondly, density influences the decisions people make about how they live, and it tends to encourage greener lifestyles.
Figure 2: Cities have a lower carbon footprint across all three sectors
The gap is particularly visible for transport emissions, with the average city resident emitting around 1.4 tonnes a year (Figure 2), compared with 2.5 for people living outside cities. Dense, well-connected, urban developments tend to have a smaller carbon footprint as journeys are often shorter, so require less energy. Data from the National Travel Survey shows that in areas classified as ‘urban conurbation’, the average distance travelled by car is 2,000 miles a year, but this rises to 4,700 miles for areas classified as ‘rural town and fringes’.4
The distance travelled is not the only important metric. The mode of transport also affects the carbon footprint of a place (Box 2). This is in part influenced by density, which facilitates the development of and demand for public transport; it also explains why emissions vary between places. In London, for instance, an average commute is around 12 kilometres, similar to places like Stoke or Slough. But transport emissions per head in the capital are respectively 40 per cent lower than in Stoke and 24 per cent lower than in Slough because London’s higher density facilitates better-quality public transport network.
The important role played by density suggests the dispersion of a place’s population matters more than its actual size. Telford and Oxford have similar populations, but Telford’s built-up area is 61 per cent larger (see Figure 4), and its transport emissions per head are twice as high as in Oxford (1.8 tonnes of CO2 against 0.9 tonnes).5 Internationally, a common comparison is Barcelona and Atlanta.6 They both have populations of about five million, but Barcelona’s dense urban form results in a much lower carbon footprint per capita.
Box 2: What are the main drivers of transport emissions?
Averaged across all cities, transport accounts for exactly one third of all carbon emissions, and is the largest source in 29 cities. Road travel (emissions from road vehicles powered by fossil fuels) is the greatest contributor, with petrol and diesel cars emitting the most, especially on a per passenger/per km basis (see Figure 3). In 2018, private cars were responsible for about 60 per cent of all transport emissions, a share that has remained fairly stable since 1990, and about 13 per cent of all greenhouse gas emissions. Vehicle improvements (such as greater fuel efficiency and more people choosing to drive electric) were offset by increases in road traffic, especially from sport utility vehicles (SUVs) and vans. Between 2009 and 2019, the number of registered vehicles rose from 33 million to 38 million, a 17 per cent increase that is well above the population growth rate.7
Figure 3: Private cars emit three times more carbon than shared modes of transport
Figure 4: Telford’s built-up area is 61 per cent larger than Oxford’s
Density impacts emissions from buildings too. This is because cities tend to have a higher proportion of flats, which generate fewer carbon emissions (Box 3). It has been estimated that the average emissions of a flat in a building with five or more dwellings is one tonne of carbon a year, compared to two for the average house.8
Much of that gap can be explained by the fact that flats tend to be smaller – in itself a function of density – as smaller dwellings emit less carbon. But size is not the only factor.
Data analysis suggests that emissions per square metre are 6 per cent lower in flats than in houses. This is because they are more heat efficient than detached homes (Box 3). They have fewer external walls, tend to share more heat with adjoining properties, and lose less through the floor and ceilings.
There are also gains that are yet to be realised from higher densities. For example, shared technologies like district heating, which can decarbonise multiple homes at once through economies of scale and supply, are only viable in dense urban environment with sufficient demand for heat.
Combined, these elements explain why domestic emissions per capita are lower in denser urban environments. That said, the gap between cities and rural areas is narrower than for transport emissions (Figure 2). This is because the quality of housing is important – many cities and large towns still have old, energy inefficient housing that is carbon hungry.9
Box 3: What are the main drivers of domestic emissions?
Averaged across all cities, domestic emissions account for 31 per cent of the total generated (the largest source of emissions in 16 cities and large towns). Most are the result of gas and electricity consumption in and around homes. The quantity of emissions is influenced by a number of factors including the types of fuel used (the burning of fossil fuels for heating being the main source of emissions); the age, type (Figure 5), quality and condition of the property (especially its size and insulation); and other household characteristics.
Figure 5: Detached houses emit more than twice as much carbon than flats
Taken together, the transport and domestic sectors explain why and how the scale of the challenge varies significantly between places (with the exception of two outliers, Swansea and Middlesbrough.)10 And so does the distance to the net zero target, as shown on Figure 6 below: cities and large towns like Warrington and Doncaster have a much higher carbon footprint that Ipswich or Worthing. And the role played by transport and housing varies, which suggests that different cities and large towns will have different challenges to address. While places like Warrington, Milton Keynes and Peterborough have high transport emissions per head, in Mansfield, Barnsley and Blackpool domestic emissions are higher.