The Summer Olympic Games are here! That means more than 300 events, ten thousand athletes and millions of spectators coming to watch. And the athletes are not the only ones with an Olympian task. The organizers of the Paris Games pledged to make their event emit only half of the carbon pollution of the 2012 London Games. 

“As an independent researcher my job is not to make people happy, but to tell them some things that are uncomfortable sometimes,” says Martin Müller, Professor of Geography and Sustainability at the University of Lausanne in Switzerland. The uncomfortable people in question are the members of the International Olympic Committee, whose offices are ten minutes down the road from Müller’s office. 

“The Summer Olympics will be anywhere between 1.5 and 4.5 million tons of CO2 equivalent. That's roughly the equivalent of a relatively large city, such as Madrid.for a year,” says Müller. The largest share of those emissions come from spectators flying in. Paris’ central location at a hub of European rail networks may make it easier this year for the crowds to avoid flying. Another factor working in Paris’ favor is the fact that they have been building out mass transit for decades. The region is in the process of building 68 new subway stations in the city and the suburbs. Most won’t be open in time for the Olympics, but a new extension from Orly Airport into the city opened in June.

The second biggest source of emissions typically comes from construction. In the past, the Olympics have been synonymous with huge infrastructure projects and iconic structures like Beijing’s Birds’ Nest Stadium. For the Paris Games, the organizers decided to take a different approach. They renovated a number of existing venues and installed a lot of temporary structures that can be used elsewhere in the future. Author and journalist Henry Grabar says, “That might not sound like rocket science, but it previously has been an approach that the International Olympic Committee has not smiled upon.” 

The big project, the Olympic Village, was built with a passive cooling system rather than traditional air conditioning, which consumes much more energy. The passive cooling system will probably be just fine for the local residents who will move into the apartments after the Olympics are gone; most Paris apartments have no cooling system at all. But no one really knows how the new system will perform in a heat wave. That has many teams worried, to the point where they have brought in their own air conditioning units. Henry Grabar says he hears athletes saying, “This is the biggest moment of my life, and so I need the room to be the exact temperature that I want it to be so I can get the perfect night's sleep before I have to go out there and literally be the best in the world at the thing I'm trying to do.” 

Martin Müller suggests that it would be better if the Olympics had no audience – or at least, a much smaller, local one – in order to prevent most of the carbon pollution that comes from travel. But for athletes, the roar of the crowd can improve their performance.  

“Athletes will not perform at the same level in an empty stadium as they would in a completely full Olympic stadium,” says Oluseyi Smith, a two-time Olympian. “But if it's a necessary trade off to ensure that the sport survives for the next 50, 60 years, I would say I'd like to think most athletes would be okay with that.” Smith is now a renewable energy engineer and Founder of Racing to Zero, a consulting group that focuses on environmental sustainability in sports. 

In Beijing, the changes made for the 2008 Olympics had surprising environmental benefits that continue to this day. 

“Prior to 2008, the air quality situation was pretty dire. Most days had exceeded what the Beijing government had identified as being a blue sky day,” says Angel Hsu, founder and director of the Data-Driven EnviroLab and teacher of public policy and the environment at the University of North Carolina-Chapel Hill. In preparation for the 2008 games Beijing expanded their mass transit, enacted rules that limited how many cars were allowed on the road, tackled heavy industry by shutting down a number of polluting factories, and tried to increase the use of renewable energy. At first, most of those initiatives were meant to be temporary. But once the people got a taste of clean air, the government made them permanent. Hsu says, “I was just in Beijing this past January and I mean, the skies are blue.”

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