Half of urban greenhouse gas emissions linked to 25 cities

A recent study published by Frontiers has calculated the amount of greenhouse gases produced by major cities globally, including 167 urban areas in various stages of development. According to the researchers, cities make up only two percent of Earth’s surface but are outsized producers of greenhouse gases. 

“Nowadays, more than 50 percent of the global population resides in cities,” said study co-author Dr. Shaoqing Chen of Sun Yat-sen University. “Cities are reported to be responsible for more than 70 percent of GHG emissions, and they share a big responsibility for the decarbonization of the global economy.”

“Current inventory methods used by cities vary globally, making it hard to assess and compare the progress of emission mitigation over time and space.”

The study found that the 25 top-emitting cities were responsible for 52 percent of all urban greenhouse gases, with cities in Europe, Australia and the United States contributing more gases per capita than cities in developing areas. 

Of the 42 sites where greenhouse gases were monitored over time, 30 had decreased their greenhouse gas emissions during the study period. In several urban areas, however, there was an increase in emissions.

Overall, 113 of the 167 cities monitored have established a greenhouse gas reduction goal, and 40 of them are striving to reach carbon neutrality. 

Unfortunately, the world is a long way from reaching many greenhouse gas reduction goals, including the targets that were established in the Paris Agreement.

The study authors recommend an approach of looking more closely at where greenhouse gases are coming from in each city – whether from transportation, waste treatment or household electricity usage. With more information, more targeted mitigation can take place. Only through a logical approach can we reduce greenhouse gases.    

The researchers also identified some of the most important sources of greenhouse gas emissions. “Breaking down the emissions by sector can inform us what actions should be prioritized to reduce emissions from buildings, transportation, industrial processes and other sources,” said Dr. Chen.

The study is published in the journal Frontiers in Sustainable Cities.

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By Zach Fitzner , Earth.com Staff Writer