Today’s cities are already responsible for about 80% of greenhouse gas emissions, according to UN-Habitat, making them in carbon terms a highly inefficient way to live. This need not be. Cities have built-in economies of scale which should allow much lower average environmental footprints for residents. Achieving these savings, however, means taking challenges like global warming, water use or waste seriously—in particular creating and modifying infrastructure elements as well as incentives to make greener lifestyles viable.

London, for example, can meet international greenhouse gas targets without a massive shift in its citizens’ life style, according to a research project carried out by McKinsey and sponsored by Siemens.

All of the carbon abatement needed to meet London’s proportional contribution to major international carbon reduction targets, as well as the majority of London’s own 2025 goal, can come from exploiting existing technology without compromising the way its inhabitants live.