British cities’ response to effects of climate change and ‘urban warming’
The UK is going to get hotter as a consequence of climate change and cities even more so, thanks to the urban heat island effect. By the 2040s, UK summer temperatures could regularly reach 38.5°C, the maximum temperature reached in the 2003 heatwave which caused approximately 2,000 deaths. Furthermore, it has been agreed that failure to adapt to climate change will result in 7,000 heat-related deaths a year by 2050.
Figure 1: Future predicted heat-related deaths
Source: House of Commons Environmental Audit Committee, 2018
One approach to adapting to rising urban temperatures is building design and retrofit. Additional insulation, vegetation and shading or overhangs and moveable window treatments all reduce the amount of heat absorbed by buildings, which in turn reduces the requirements for air conditioning. Low absorption building fabric materials and designs that maximise internal airflow also help reduce internal building temperature. However, in current building regulations, overheating risk is not sufficiently addressed. Given the increase in media attention paid to heatwaves it is likely that this omission will be rectified by 2040. But it will take time to bring all buildings up to standard. In 2040, while progress will be made, a large number of buildings in UK cities will overheat.
On a slightly larger scale, green space has been proven to reduce the urban heat island effect. Although urban areas can be up to 10°C hotter than surrounding rural areas, urban green spaces can reduce urban air temperatures by 2°C - 8°C. While urban green space (see our related article here) has declined in England, from 63% in 2001 to 56% in 2016, and the new National Planning Policy Framework makes no mention of the urban heat island effect, a number of cities have nevertheless set targets to increase their green space.
For example, Bristol City Council has stated it intends to increase the City's tree canopy from 15% to 30% by 2050. Greater Manchester has also begun discussing becoming a city of trees. We write more about urban trees elsewhere.
Although green space remains under threat we expect that this will not stop more cities adopting plans to increase this within their cities. Many will be inspired by Bristol and Manchester’s well-received plans and the continued success of Singapore, whose 4,000 hectares of green space has reduced temperatures by up to 2°C - 3°C.
Where does the responsibility for adaptation lie? Although adaptation adjusting to heatwaves will require a co-ordinated response with national, local, and devolved governments, ultimate responsibility lies with the Department for Environment, Food and Rural Affairs and the Department for Health and Social Care. However, the current minister for public health does not consider it part of their responsibility.
The Committee on Climate Change has criticised the complex governance arrangements as a barrier to effective adaptation. In 2040, a range of adaptation policies are likely to have been developed and implemented at the local government level, legitimised by a national framework.
And adaptation is really the right word. This is not an issue that cities can easily build their way out of through the replacement of their existing stock. Because most of the urban fabric that will exist in UK cities in 2040 has already been built, policies focusing on adaption and retrofit will be essential, alongside ‘urban greening’. While new buildings can make a contribution, paying attention to the existing stock looks likely to recoup larger dividends in the next twenty years.