Bejing often suffers choking air. But there's now one more thing proven to dissipate it: an Olympics.

The 2008 summer games impelled those in charge of the Chinese capital to clear the air. Not only did they banish smog and smoke, they also inadvertently cut greenhouse gas emissions by as much as 96,000 metric tons during the games. That's according to a new analysis published in Geophysical Research Letters on July 20th. [Helen M. Worden et al., Satellite-based estimates of reduced CO and CO2 emissions due to traffic restrictions during the 2008 Beijing Olympics]

The key was banning half of all the private cars in the city from driving on any particular day during the event. The finding suggests that individual choices like whether to drive or take public transit to work have major cumulative effects.

London's so-called congestion charge for driving in town likewise cuts traffic and pollution. This year, London is bidding to have the most environmentally friendly Olympics ever.

That includes building new stadiums atop former industrial sites and urging fans to choose public transit, walking or cycling. But the British may not match the Chinese achievement, or even attempt to make the London games carbon neutral. The Olympics that finally achieves zero carbon would really merit a gold, for green.

—David Biello

[The above text is a transcript of this podcast.]