Researchers have taken a look at the carbon footprints of 13,000 cities in a large study of the world's urban areas.

A study on the findings, led by the Norwegian University of Science and Technology, was published in Environmental Research Letters. The team looked at the carbon emissions of each city, and then ranked them in order. A city in this study was defined as being a “contiguous densely populated area”.

The top was Seoul in South Korea, outputting about 276.1 tonnes (304.4 tons) of carbon dioxide each year. Next on the list were Guangzhou in China, New York in the US, Hong Kong in China, and Los Angles in the US.

London in the UK came in at number 16, while Beijing in China was number 18. New Delhi in India only came in at number 30, despite a population of 27 million, while Sau Paulo in Brazil was all the way down in 63rd, despite a population of nearly 20 million.

Here’s the top 10 list, with their annual carbon emissions in tonnes shown in brackets. You can check out the interactive map here.

1. Seoul, South Korea (276.1)

2. Guangzhou, China (272.0)

3. New York, US (233.5)

4. Hong Kong, China (208.5)

5. Los Angeles, US (196.4)

6. Shanghai, China (181.0)

7. Singapore (161.1)

8. Chicago, US (152.9)

9. Tokyo, Japan (132.8)

10. Riyadh, Saudi Arabia (118.8)

Perhaps the most surprising thing from the findings was how concentrated emissions were. The researchers found that the top 100 cities were responsible for 18 percent of the global carbon footprint, suggesting changes at a local level could have a dramatic effect on emissions.

"The top 100 highest-footprint cities worldwide drive roughly 20 percent of the global carbon footprint," Daniel Moran, the study’s lead author, said in a statement. "This means concerted action by a small number of local mayors and governments can significantly reduce national total carbon footprints."

The team also found that urban areas are home to about 54 percent of the total global population, and account for 70 percent of global energy use. And it also seems that income is a strong indicator of carbon footprint, with the top 600 urban centers responsible for 60 percent of global GDP.

"The fact that carbon footprints are highly concentrated in affluent cities means that targeted measures in a few places and by selected coalitions can have a large effect covering important consumption hotspots," Moran added.