The climate crisis is getting worse, with both the Intergovernmental Panel on Climate Change (IPCC) and COP28 in its final agreement emphasizing the urgency of steep greenhouse gas emissions reductions to keep global warming below 1.5°C as overshooting 1.5° C might have a catastrophic impact.
Given that urban areas may account for over 70 percent of global CO₂ emissions, many public policy analysts began advocating for public investment in low-carbon mass transit, particularly in countries that are not yet locked into high-carbon growth paths, as one of the solutions. Until recently, however, data scarcity has hindered assessment of mass transit’s impact on CO₂ emissions.
Quantifying subway systems’ impact on CO₂ emissions
Recent World Bank research used new satellite data to quantify the impact of subway investments. Subways’ impacts on CO₂ emissions were assessed with the help of World Bank’s new satellite-based carbon emissions database, which provides consistent measures across space and time of CO₂ emissions from urban areas. The research covered 1,474 urban areas with populations exceeding 500,000, measuring subway impacts after accounting for source differences (e.g., industries, fires, motor vehicles, cooling, heating) in cities and nearby areas. Results indicate subways have had a huge impact on CO₂ emissions in urban areas where they operate.