Millward-Hopkins Joel, Gouldson Andrew, Scott Kate, Barrett John, Sudmant Andrew
Sustainability Research Institute, University of Leeds, Leeds, UK.
Reg Environ Change. 2017;17(5):1467-1478. doi: 10.1007/s10113-017-1112-x. Epub 2017 Feb 3.
The rapid urbanisation of the twentieth century, along with the spread of high-consumption urban lifestyles, has led to cities becoming the dominant drivers of global anthropogenic greenhouse gas emissions. Reducing these impacts is crucial, but production-based frameworks of carbon measurement and mitigation-which encompass only a limited part of cities' carbon footprints-are much more developed and widely applied than consumption-based approaches that consider the embedded carbon effectively imported into a city. Frequently, therefore, cities are left blind to the importance of their wider consumption-related climate impacts, while at the same time left lacking effective tools to reduce them. To explore the relevance of these issues, we implement methodologies for assessing production- and consumption-based emissions at the city-level and estimate the associated emissions trajectories for Bristol, a major UK city, from 2000 to 2035. We develop mitigation scenarios targeted at reducing the former, considering potential energy, carbon and financial savings in each case. We then compare these mitigation potentials with local government ambitions and Bristol's consumption-based emissions trajectory. Our results suggest that the city's consumption-based emissions are three times the production-based emissions, largely due to the impacts of imported food and drink. We find that low-carbon investments of circa £3 billion could reduce production-based emissions by 25% in 2035. However, we also find that this represents <10% of Bristol's forecast consumption-based emissions for 2035 and is approximately equal to the mitigation achievable by eliminating the city's current levels of food waste. Such observations suggest that incorporating consumption-based emission statistics into cities' accounting and decision-making processes could uncover largely unrecognised opportunities for mitigation that are likely to be essential for achieving deep decarbonisation.
二十世纪的快速城市化，以及高消费城市生活方式的传播，已导致城市成为全球人为温室气体排放的主要驱动因素。减少这些影响至关重要，但基于生产的碳测量和减排框架——仅涵盖城市碳足迹的有限部分——比考虑有效输入城市的隐含碳的基于消费的方法更为发达且应用广泛。因此，城市常常对其更广泛的与消费相关的气候影响的重要性视而不见，同时又缺乏减少这些影响的有效工具。为了探讨这些问题的相关性，我们实施了在城市层面评估基于生产和消费的排放的方法，并估计了英国主要城市布里斯托尔从2000年到2035年的相关排放轨迹。我们制定了旨在减少前者的减排情景，每种情景都考虑了潜在的能源、碳和资金节约。然后，我们将这些减排潜力与地方政府的目标以及布里斯托尔基于消费的排放轨迹进行比较。我们的结果表明，该城市基于消费的排放是基于生产的排放的三倍，这主要是由于进口食品和饮料的影响。我们发现，约30亿英镑的低碳投资可使2035年基于生产的排放减少25%。然而，我们还发现，这仅占布里斯托尔2035年预测的基于消费的排放的不到10%，大致相当于通过消除该市目前的食物浪费水平所能实现的减排量。这些观察结果表明，将基于消费的排放统计纳入城市的核算和决策过程，可能会发现大量未被认识到的减排机会，而这些机会对于实现深度脱碳可能至关重要。
