Handful of cities driving urban emissions: Study

LONDON • Just 25 big cities - almost all of them in China - accounted for more than half of the climate-warming gases pumped out by a sample of 167 urban hubs around the world, an analysis of emissions trends showed.

In per capita terms, emissions from cities in the world's richest parts are still generally higher than those from urban centres in developing countries, researchers found in the study published yesterday in the Frontiers journal.

The study compared greenhouse gas emissions from 167 cities in 53 countries, and found that 23 Chinese cities - including Shanghai and Beijing - along with Moscow and Tokyo accounted for 52 per cent of the total.

It included more cities from China, India, the United States and the European Union because of their larger contribution to global emissions and significance to the climate debate.

The findings highlighted the significant role cities play in cutting emissions, said study co-author Chen Shaoqing, an environmental scientist at Sun Yat-sen University in Guangzhou. "It is simple, logical," he said. "If you don't act, eventually you will suffer."

Average global temperatures have already risen by more than 1 deg C compared with the pre-industrial baseline and are still on track to exceed the 1.5 to 2 degree limit set by the Paris Agreement.

Dr Chen and other scientists cautioned, however, that some of the data used in their study was patchy, with some cities reporting numbers from as far back as 2005.

A lack of consistency in how cities report emissions also makes comparisons tricky, they added.

Research published in 2018 in the Environmental Research Letters analysed a much larger sample of 13,000 cities, finding that 100 cities containing 11 per cent of the world's population drove 18 per cent of its carbon footprint.

Still, the new analysis "contributes to the growing literature and our understanding of urban emissions", said Yale University's Professor Karen Seto, who co-authored the 2018 paper.

Dr Chen said the new analysis was the first to look at megacity emissions reduction targets and progress in cutting back.

Sixty-eight of the cities, mostly in developed nations, had set absolute emissions reduction targets. But only 30 of 42 cities where progress was tracked in the study had shown a reduction. Most of them were in the US and Europe.

The analysis confirms scientists' expectations that whereas in China, cities with high per capita emissions are generally major manufacturing hubs, those in developed nations with the highest per capita rates tend to have strong levels of consumption.

While more developed economies in Europe and elsewhere can now grow without increasing emissions, the world is moving at different speeds, Dr Dan Hoornweg, former adviser to the World Bank on sustainable cities and climate change, said.

"They generated a tonne of emissions on the way to get there and China is in that stage now. We know India is getting there at some point and the last big push in all of this will be Africa," he said.

REUTERS