Long a mainstay of environmental policy, emissions trading programs have faced increasing criticism in recent years. Critics have assailed trading programs for failing to generate the scale of greenhouse gas emissions (GHG) reductions necessary to mitigate the climate crisis and have argued that trading exacerbates the burdens imposed on environmental justice communities. This essay offers a qualified defense of trading. Drawing upon our experience leading a large-scale study of emissions for trading for New York City, we suggest that trading could help cities effectively reduce GHG emissions from buildings. We further suggest that, if carefully designed, trading could affirmatively advance environmental justice goals by increasing the level of investment in environmental justice communities and reducing more air pollution in these areas.