Low-carbon infrastructure strategies for cities

Reducing greenhouse gas emissions to avert potentially disastrous global climate change requires substantial redevelopment of infrastructure systems(1-4). Cities are recognized as key actors for leading such climate change mitigation efforts(6-10). We have studied the greenhouse gas inventories and underlying characteristics of 22 global cities. These cities differ in terms of their climates, income, levels of industrial activity, urban form and existing carbon intensity of electricity supply. Here we show how these differences in city characteristics lead to wide variations in the type of strategies that can be used for reducing emissions. Cities experiencing greater than similar to 1,500 heating degree days (below an 18 degrees C base), for example, will review building construction and retrofitting for cold climates. Electrification of infrastructure technologies is effective for cities where the carbon intensity of the grid is lower than similar to 600 tCO(2)e GWh(-1); whereas transportation strategies will differ between low urban density (< similar to 6,000 persons km(2)) and high urban density (> similar to 6,000 persons km(-2)) cities. As nation states negotiate targets and develop policies for reducing greenhouse gas emissions, attention to the specific characteristics of their cities will broaden and improve their suite of options. Beyond carbon pricing, markets and taxation, governments may develop policies and target spending towards low-carbon urban infrastructure.