Despite initiatives like an idle-free zone in front of Calgary City Hall, the city is Canada's top CO2 emitter, according to a UN report. (CBC)

Calgary produces more carbon dioxide per person in an urban setting than smog-filled Mexico City or New York City, according to a report by the United Nations.

Going by new international measuring standards, Calgary produces 17.7 tonnes of carbon dioxide per capita, ranking it fifth-highest in a comparison of 50 global cities.

Toronto and Vancouver, the only other Canadian cities surveyed, had emissions of 9.5 tonnes and 4.9 tonnes, respectively. That brings them near the middle of the pack, along with Tokyo and Mexico City.

The electrical grids in those cities run on hydro or nuclear power, whereas Calgary relies on coal-fired electrical plants that create more emissions.

"Calgarians get their power from burning coal. They live in a fairly sprawling city and because we have large homes and we really have no climate regulations in Canada, it's not surprising at all," said Chris Severson-Baker of the Pembina Institute on Tuesday.

"Every time they turn on the lights, turn on their TV, they're essentially burning coal, and that is a significant source of greenhouse gas emissions and something we could do a lot of work on to reduce."

Calgary's heavy reliance on vehicles is part of its high ranking, said Jim Prentice, Calgary MP and federal environment minister. (CBC)

The UN Environment Programme report was prepared for last month's World Urban Forum. Only Washington, D.C., Minneapolis, Denver and Rotterdam, Netherlands produced more CO2 than Calgary, according to the study.

"It is not a good position for the city to be in," said Rick Ciezki, the City of Calgary's manager of environmental assessment and liabilities. "Obviously we want to improve that and drop lower, if not completely off the list."

The UN used statistics from 2003 provided by the city. Even taking into account green initiatives — such as wind power running the C-Train system and greening the city's corporate electricity use by 2012 — Ciezki said the UN's rating is likely fair.

"I wouldn't dispute them necessarily. We do have a higher emission number and higher ecological footprint. I think the thing to emphasize here is the work we're doing to reduce that," he said.

Federal Environment Minister Jim Prentice, who is an MP for Calgary, acknowledged the city's high ranking also comes from Calgarians' heavy use of vehicles.

"In any city there's certainly room for improvement," he said from Ottawa.

Higher density, fewer emissions

The UN findings suggest cities with higher densities such as New York City generate fewer emissions per person.

Calgary Ald. Brian Pincott, who sits on the city's environment committee, said higher density — in general, where residences, amenities, and public transit are built close together — can help, but only if it's done correctly.

"What does that density look like? What does the transportation look like? Where do you actually buy your groceries? Where are your schools? Do you walk to those things? Where are your jobs?" said Pincott.

"How do you live in relation to public transit? It's those kinds of things that have to go into making a sustainable, viable, livable city."