Cities with policies to cut fossil-fuel emissions have also seen economic growth.Credit: Westend61/Getty
For most of modern history, economic growth has been tightly coupled with the use of fossil fuels. Cities now house more than half of the world’s population, and that urbanization has come hand-in-hand with ecological degradation, air pollution and greenhouse-gas emissions.
But now, an assessment of 2,475 of the world’s biggest cities has found that in 80% of them, economic growth is no longer dependent on an increase in fossil-fuel-related emissions. The study, published today in Nature Cities1, used satellite data to measure levels of the greenhouse gas nitrogen dioxide (NO2) emitted from cities, and compared these data with information on gross domestic product (GDP). The findings indicate that almost 2,000 cities worldwide have implemented green policies that generated economic prosperity while reducing dependencies on fossil fuels.
“This research is revealing the importance of cities in addressing twenty-first-century sustainability challenges,” says Michail Fragkias, an applied economist at Boise State University in Idaho, who was not involved in the work.
Green cities
In their study, Daniel Moran, an environmental economist at the Norwegian Institute for Air Research in Kjeller and his colleagues used satellite data from the European Union’s Copernicus Sentinel-5P satellite mission to measure NO2 levels in the troposphere above cities between January 2019 and December 2024. NO2 is produced when fuel is burnt in vehicles, power plants and industrial facilities. The team combined this emissions data with local GDP information per capita for the same period to create an indicator of economic activity linked with fossil-fuel use. This allowed Moran to “see the green development trajectory over time of cities globally”.
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The study measured 5,435 cities in total, but 2,919 of them showed no significant change in their amount of NO2 so were excluded from further analyses. Forty-one were also removed because of unreliable GDP data. Of the remaining 2,475 cities, 80% showed a significant increase in GDP per capita and a reduction in NO2 levels. Moran and his colleague termed these cities with decreasing emissions and growing prosperity as ‘green’.
Fragkias says the study’s definition of greenness is broad, but that it is “highly encouraging” that four out of five cities with significant trends are showing signs of being able to grow without remaining dependent on fossil fuels, thanks to green policies.
