There are roughly 10,000 cities in the world, defined as places with at least 50,000 inhabitants with a sufficient population density. Roughly half the world’s population lives in cities.
Urban carbon emissions are one of the world’s biggest problems with respect to the climate. A new study has determined that just 25 cities globally are responsible for 52% of urban greenhouse gas emissions.
The study gathered data on greenhouse gas emissions in 167 cities in 53 countries. The results were that megacities in Asia, such as Shanghai and Tokyo, were among the biggest total emitters, and that major cities in Europe, the US, and Australia tended to have larger per capita emissions. Several Chinese cities, however, matched levels seen in developed countries. Researchers tracked emissions over time in 42 of the cities studied. Some cities saw declining emissions in the period between 2005 and 2016. These included Oslo, Houston, Seattle, and Bogota. Others saw large increases, including Rio de Janeiro, Johannesburg, and Venice.
The largest sources of emissions are power generation, industry, and transportation. In a third of the cities, road transportation alone accounted for over 30% of emissions. (Railways, waterways, and aviation combined only accounted for less than 15% of total emissions).
Half of the world’s population lives in cities, but cities are responsible for more than 70% of greenhouse gas emissions. Thus, cities have a big responsibility for the decarbonization of the global economy. Of the 167 cities in the study, 113 have set emission-reduction targets. But as the study shows, cities have much more work to do to meet the goals of the Paris Climate Agreement.
Photo, posted December 1, 2017, courtesy of Hector Galbis via Flickr.