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 on Monday.

In per capita terms, however, emissions from cities in the richest parts of the world are still generally higher than those from urban centres in developing countries, researchers found in the study published in the open access journal Frontiers in Sustainable Cities.