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C200: Cities as a Solution to Climate Change

2011 March 28
by Peter Erickson

The task of averting the worst impacts of climate change is unbelievably daunting. Global greenhouse gas emissions must peak this decade and decline rapidly—to less than 1 ton CO2e per capita—within just a few decades.

Cities are on the front lines of this challenge.  Nearly 70% of the world’s population is expected to live in cities by 2050.   The way cities are built – and rebuilt – has profound implications for their contribution to—and resilience against—climate change.

For example, dense, lively, pedestrian- and transit-oriented cities can help us move around with much lower greenhouse gas emissions: as low (or even below) 1 ton CO2e per capita (see graph below), compared to a national U.S. average of 4 tons CO2e per person for ground transportation (largely cars).

< GHG Emissions from Ground Transportation are Inversely Proportional to Density >

Yet the full annual emissions footprint of a U.S. resident averages about 29 tons CO2e/capita, including significant emissions from sources well beyond the city border, such as air travel and emissions needed to make the food we eat and products we use.   Even a dense, vibrant—heck, even car-free city—couldn’t (on its own) avoid these other emissions.

Cities are complex, wonderful systems that, by their very nature, can help orient us to low-GHG lifestyles, particularly for daily transportation.  Once we get our cities on that path, next up: can our cities, with their convergence of people and capital, also transform the rest of the economy?


Peter Erickson is a staff scientist in the Seattle office of the Stockholm Environment Institute.