July 6 (UPI) -- In wealthier countries, per capita air pollution and CO2 emissions in major cities have been declining over the last few decades, according to a new study.
The findings, published Tuesday in the journal Environmental Research Letters, showed urban emissions increased dramatically in developing countries during the last 50 years.
Between 1975 and 2015, Earth's human population increased by 80 percent. But while urban populations nearly doubled, rural populations increased by only 40 percent.
Today, nearly half of all people on Earth live in urban centers, and nearly a quarter live in the largest urban centers, cities with a population of at least 1 million people.
As a result of these demographic trends, urban centers have come to account for more and more of humanity's carbon footprint.
To better understand how shifts in the spatial distribution of Earth's human residents have influenced global emissions, scientists with the European Commission analyzed data collected by the Emissions Database for Global Atmospheric Research, EDGAR.
Their analysis showed nearly half of global emissions, both air pollutant and greenhouse gases, emanate from just 1 percent of global surface.
When all urban areas and suburbs are lumped in with large urban centers, urban populations account for between 70 and 80 percent of global emissions.
Between 1975 and 2015, urban emissions increased all over the world. However, the latest analysis showed per capita urban emissions have increased most significantly in developing nations, where urban populations have increased most dramatically.
Conversely, per capita urban emissions have decreased across most of the developed world. In wealthier nations, the latest research suggests deindustrialization and mitigation actions have helped decrease carbon emissions and air pollution.
With the decline of industrial activities and the growth of the service economy, urban centers in wealthier countries have been able to decouple economic growth from emissions.
But researchers suggest concerted mitigation efforts have also helped urban centers in wealthier countries decrease their carbon footprint and improve air quality.
The authors of the latest study suggest these efforts can be used to inform policy making in urban centers across the developing world.
"While climate change is a global issue, air quality is a more local problem to be tackled in order to reduce urban population exposure to harmful pollutants and finally to reduce human health impacts and those on ecosystems," researchers wrote. "Local actions are therefore needed for both climate and air pollution."