It's been an unfortunate iron law of the modern era that greenhouse gas emissions grow at the same time that economies do. The higher the standard of living in a country or metro area, the larger, per capita, its environmental footprint becomes. In practice, this means that wealthier economies trade foot traffic for cars, small homes for larger ones, local travel for airplane tickets, small-scale industry for major manufacturing, and homemade products for cheaper goods produced half a world away.
Research has shown that if you know a country's GDP, you can pretty accurately estimate its carbon emissions. There's "almost a mechanical relationship" between the two. And as a depressing corollary: Emissions rise much faster in good times than they fall during, say, a global recession.
Cities in some parts of the world are already doing a substantially better job at decoupling these two trends than others, wringing the most wealth out of the smallest carbon footprint. These are the cities that produce the greatest amount of GDP per ton of greenhouse gasses emitted. The Carbon Disclosure Project, along with AECOM and the C40 Cities, have calculated this "economic efficiency" for dozens of global cities that participated in a questionnaire on how they are preparing for climate change.