05Progress against the UK’s carbon budgets: how much will cities contribute?
The changes discussed in the previous section of this report, whether they aim to disincentivise car use or upgrade currently energy inefficient housing stock are likely to achieve significant cuts in carbon emissions in the transport and domestic sector, respectively. This section looks at the combined impact of these changes when set against the UK’s overall carbon emissions reductions target.
The UK recently enshrined into law its Sixth Carbon Budget for 2035, which includes a commitment to reach a 78 per cent reduction in greenhouse gas emissions compared to 1990. This corresponds to a 63 per cent cut compared to current levels. Translating this objective into annual budgets shows the scale of the challenge: by 2035, the UK’s total emissions need to be below 200Mt, compared to more than 500Mt today.
Data analysis suggests that if, by 2035, cars only account for a third of all journeys, and all houses currently graded below EPC band C have been upgraded, then about 26 per cent of the total cuts needed to be in line with a net zero trajectory can be achieved.
It is clear that these changes alone will not be enough to reach net zero. More action will be required in the industry, waste, aviation or shipping sectors, for example. But in terms of the sectors local authorities have some level of control over, such as housing and transport, this analysis confirms that cities and large towns have the potential to disproportionately help the UK meet its emissions target. This is shown in Figure 14: because of their density, cities and large towns will account for 57 per cent of the total cuts achieved, against 43 per cent in the rest of the UK.
Figure 14: Cities can help achieve a disproportionate share of emissions cuts needed
Not all places will need to cut emissions at the same pace – nor do they have the potential to do so. Figure 15 below is based on a calculation of local carbon budgets (Box 10) which are then translated into an annual target for 2035. It looks at the impact of the changes discussed in transport and housing, against the overall cuts needed in each city or large town.
Figure 15: Not all cities have the same potential to reach emission cuts
In Ipswich and Worthing, these changes in housing and transport could account for about half of the total objective, while in Middlesbrough and Swansea, it is less than 10 per cent due to the current composition of emission sources.36
These calculations also confirm which policy levers cities and large towns should prioritise: while London, Cambridge or Bradford will have to put the emphasis on reducing domestic emissions, in Milton Keynes, Aldershot and Northampton (where housing stock is newer because of their post-war creation or expansion), tackling transport emissions will be crucial.
Box 10: How are carbon budgets calculated?
Since cumulative emissions from human activity are the main driver of an increase in global average temperatures, the imperative for the decades to come is to control and reduce the amount of carbon emitted into the atmosphere. The Intergovernmental Panel on Climate Change has estimated that the global total amount of carbon that can be deposited into the atmosphere between now and 2100, with a “likely” chance of staying well below two degrees, in line with the 2015 Paris Agreement, is 900 GtCO2. This is a carbon budget, which is a measure of the total amount of carbon dioxide that can be emitted into the atmosphere by a given date.
At the national scale, there is not a single carbon budget, as a number of institutions have calculated their own value for the UK based on a wide range of different scenarios- such as the likelihood of limiting global warming to 1.5°C, or the reliance on carbon removal technologies. Researchers at the Tyndall Centre for Climate Change Research have recently developed a local carbon budget tool, using a method called ‘grandfathering’ which downscales the global carbon budget to a UK budget and then to local areas based on their respective recent shares in global and national emissions.37 38
Applying the same method at the scale of the Primary Urban Area can therefore be used to calculate the remaining amount and share of carbon that can be emitted from the UK’s 63 largest cities and towns, in line with the Paris Agreement objectives. The total size of the carbon budget varies from place to place: given its share in national emissions, London’s budget is the largest: the capital must stay within a maximum cumulative budget of 230 MtCO2, while in other places like Cambridge and Worthing the total budget is much smaller (less than 5Mt).
This calculation confirms that to remain below their respective budget and help the UK achieve its net zero target, the pace of change needs to accelerate significantly. On their current trajectories, most cities and large towns are set to expend their total budget in fewer than seven years from now.