We know that city dwellers have a smaller carbon footprint that suburbanites. But now we have a real case study with carbon measurements to document the phenomenon.

14 scientists at the National Center for Atmospheric Research, the University of Utah and several other universities set up a network of carbon dioxide sensors across Salt Lake City and its suburbs. The Washington Post reported on the results:

As suburbs have expanded southwest of Salt Lake City over the last 10 years, carbon dioxide emissions have spiked…

It’s the latest indication that suburban expansion takes an environmental toll, with people driving greater distances and building larger homes that use more energy for heating and cooling.

Similar population growth in the center of Salt Lake City didn’t take the same toll, according to the research. Carbon dioxide emissions in the city center were already higher than in nonurban places. But as the population there grew by 10,000 people, the emissions didn’t increase further.

It’s yet more evidence that encouraging urban growth is one of the most important steps we can take to reduce greenhouse gas emissions. And it’s also a reason why supposedly “environmental” organizations like Sierra Club California that oppose pro-infill measures like SB 827 are actually damaging the environment by doing so.