Workers refurbish a cruise ship in Rotterdam, Netherlands, in 2005. According to a new study, Rotterdam is one of the "dirtiest" cities in the world when it comes to emissions of carbon dioxide (CO2) and methane. The two are by far the most plentiful greenhouse gases emitted by cities and major contributors to global warming, according to study co-author Dan Hoornweg.
The study, which analyzed emissions figures for 100 cities in 33 countries, determined that, for every one of its residents, Rotterdam is responsible for the annual emission of about 29.8 tons of CO2 and methane, combined.
The figure "reflects the large impact of the city's port in attracting industry, as well as fueling of ships," according to the report.
The study looked at how much CO2 and methane a city produces each year based on consumption by residents and industries within city limits. Still, Hoornweg cautions against seeing the report as an indictment of cities in general.
"Differences in production and consumption patterns between cities and citizens mean that it is not helpful to attribute emissions to cities" to the exclusion of suburbs and rural areas, Hoornweg, lead urban specialist at the World Bank in Washington, D.C., said in a statement.
Around the world, emissions per person per year were found to vary from 5 to 25 tons of CO2 and methane for cities in industrialized nations to less than half a ton per person per year in some South Asian cities.