Assessing global urban CO2 removal

Abstract

Cities worldwide are increasingly committing to achieving net-zero carbon emissions in the coming decades. Most cities are not yet aware of the drastic changes in built environment required to reduce GHG emissions, and in many cases carbon neutrality targets will require atmospheric carbon removal outside or within city boundaries to offset remaining emissions. Since cities are particularly affected by increasing temperatures (e.g. due to the urban heat island effect), direct regulation of radiation through surface albedo management has also been suggested to alleviate these exacerbated urban heat impacts. With the aim of supporting the path to carbon-neutral cities, this paper assesses the existing literature on Carbon Dioxide Removal (CDR) at the urban scale, seeking to quantify the potential negative emissions contribution of cities globally. Our potential estimates indicate that deploying CDR options at the urban scale could make a significant contribution to global mitigation of climate change, alongside supporting the upscaling of climate action from local to regional and national scale. The associated human and environmental well-being effects strengthen the case for cities as carbon sinks. The upscale of the reviewed technologies is nevertheless constrained by numerous uncertainties, economic barriers and governance issues that pose substantial drawbacks to their implementation and scope, suggesting a future research agenda.