The largest benefits for reducing the impacts of global climate change may be attained when global and local initiatives are implemented togetherThe aim of this study was to quantify the effects and interactions of global and local climate change as well as of local and global climate policy. A specific focus was on the economic ramifications of the joint impacts of local and global climate change on cities around the world. While cities cover around 1% of the Earth’s surface, they consume about 78% of the world’s energy and produce more than 60% of all CO2 emissions. Additionally, 54% of the world’s population live in cities. By 2050, this is expected to be about 66%.
Current studies on the impacts of climate change in cities are generally qualitative and focus mostly on a limited number of countries and risks. Additionally, they fail to take into account the fact that large cities will experience additional warming due to the urban heat island (UHI) effect, -- that is, the change of local climate patterns caused by urbanization. The UHI effect occurs when vegetation and water bodies are replaced by such materials as concrete and asphalt, which have higher heat capacities and thermal conductivity. This process causes changes in the local climate, such as higher temperatures and shifts in precipitation and wind patterns. Adverse outcomes include increased energy use for cooling, higher emissions of air pollutants, human health risks, and lower water quality.
Cities typically have little control over energy and agricultural policies which can be key elements in reducing greenhouse emissions. However, there are steps cities can take to lessen the UHI effect, such as installing green roofs, cool pavements, and more vegetation. This study includes a cost–benefit analyses of such urban heat island mitigation efforts.
Compared with global efforts, some local actions to improve urban climate have the advantage of being easier to implement and result in more immediate benefits. Local mitigation actions also have global implications. The largest benefits for reducing the impacts of global climate change may be attained when both global and local initiatives are implemented together. When global and local efforts are combined, the outcomes are likely to be greater than the sum of the parts.
This study suggests that limiting the urban heat island effect through city adaptation efforts can significantly amplify the benefits of international mitigation efforts, including important economic benefits for almost all cities around the world. Methods of arriving at these conclusions along with data sources are provided in the online version of this paper.
The Bottom Line