"In Paris, a carbon sniffer originally tucked away in the Eiffel Tower's observation deck had to be moved to a higher floor that's off-limits to the public after tourists' exhaling interfered with the data"

Watch your breath megacities: Project aims to track greenhouse gases from LA, Paris - ktuu.com

This summer, technicians will install commercial gas analyzers at a dozen more rooftops around the greater LA region. Scientists also plan to drive around the city in a Prius outfitted with a portable emission-measuring device and fly a research aircraft to pinpoint methane hotspots from the sky. (A well-known natural source is the La Brea Tar Pits in the heart of LA where underground bacteria burp bubbles of methane gas to the surface.)
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Launching the monitoring project came with the usual growing pains. In Paris, a carbon sniffer originally tucked away in the Eiffel Tower's observation deck had to be moved to a higher floor that's off-limits to the public after tourists' exhaling interfered with the data.

So far, $3 million have been spent on the U.S. effort with funding from federal, state and private groups.