Scientists from throughout the world are tracking the the carbon footprints of some of the earth's largest cities, to see if emissions standards in those locations are being met.
The research effort is at least initially focusing on Los Angeles, Calif., which boasts a population of nearly 4 million, and Paris, France, which claims about 2.2 million residents.
Their efforts of the wide team of researchers coincided with a report this last weekend issued by the National Oceanic and Atmospheric Administration that atmospheric carbon dioixde levels had surpassed 400 parts per million (ppm) for the first time in recorded human history. Later reports contradicted the record-breaking announcement, saying the CO2 had indeed grazed the high mark, but hadn't crossed it yet.
The last time carbon dioxide levels had reached 400 ppm was millions of years ago, during the Pleistocene Era, according to NOAA.
Sir Brian Hoskins, head of climate change at the UK-based Royal Society, told BBC News he hoped the specter of the gaseous milestone would "jolt governments into action" and increase efforts to battle global warming.
The tracking project in fact predates the recent media buzz over the carbon milestone, as a high-tech sensor on Mount Wilson, which overlooks the L.A. Basin, has been observing the Socal area for more than a year, scanning over two dozen points in the region and measuring sunlight reflecting off the surface for carbon dioxide and other heat-trapping gases.
"There are some days where we can see 150 miles way out to the Channel Islands and there are some days where we have trouble even seeing what's down here in the foreground," Stanley Sander, a senior research scientist with the National Aeronautics and Space Administration's Jet Propulsion Laboratory, set near the foot of Mount Wilson, told the AP.
Sander and of JPL researchers said they plan to increase the observation network --- installing commercial gas analyzers at several new locations throughout the area over the next few months --- in an effort to see if the city is on track to meet its goal of cutting emissions to 35 percent below 1990 levels by 2030.
Similar efforts were launched in Paris and elsewhere, the AP reported, but were met with some rather unusual challenges, including the fact a monitoring device located on the observation deck of the Eiffel Tower had to be moved after it was found visitors to the French landmark were affecting study readings --- by breathing.