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...
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