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New Study Shows 25 Mega-Cities Producing 1.2 Gigatonnes of CO2

Child cycling with a mask

Just 25 mega-cities, 23 of them in China, accounted for more than half of the greenhouse gas emissions produced by a collection of 167 urban centres assessed in a new study in the open access journal Frontiers in Sustainable Cities.

The 53-country sample, based on local emissions figures that are now five to 16 years old, was compiled by researchers at Sun Yat-sen University in Guangzhou. It shows that “China in particular will need to step up its switch from coal to renewables” to meet its own goals under the Paris climate agreement, the Daily Mail Online writes.

The nine Chinese cities in the top 10, including Shanghai, Beijing, Tianjin, and Wuhan, accounted for
1,225 million tonnes (1.225 gigatonnes) of carbon dioxide or equivalent emissions, the Mail Online
reports, based on reference years ranging from 2005 to 2016. Moscow placed seventh, with 112.53
million tonnes of emissions, while Tokyo came in 17th, with 66.08 Mt. New York City was the biggest
North American source in the survey, placing 26th with 51.31 megatonnes, while Toronto came in 74th
with 18.08 Mt.

Out of 42 cities with data that spanned the period from 2012 to 2016, 30 reduced their emissions, the
researchers found. Oslo, Houston, Seattle, and Bogotá showed the biggest cuts, while Rio de Janeiro,
Curitiba, Johannesburg, and Venice recorded the biggest increases.

Overall, the study concluded the municipalities were not on track to meet the Paris agreement target of holding average global warming to 1.5°C.

“Cities are reported to be responsible for more than 70% of GHG emissions, and they share a big
responsibility for the decarbonization of the global economy,” said study author Shaoqing Chen, an
urban environmental research manager at Sun Yat-sen. He urged municipalities to “set more ambitious and easily-traceable mitigation goals,” adding that at some point those goals must move beyond shifts in emissions intensity to actual reductions in carbon pollution.

“At a certain stage, carbon intensity is a useful indicator showing the decarbonization of the economy
and provides better flexibility for cities” in times of rapid economic growth, he said. “But in the long
run, switching from intensity-based mitigation targets to absolute mitigation targets is essential to
achieve global carbon neutrality by 2050.”