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LISA NAPOLI: Okay, now that we’ve ruined your morning with the threat of asteroids, let’s talk about a more immediate threat: greenhouse gas emissions and a Carbon Tracker to measure them. Here’s Sam Eaton from the Marketplace Sustainability Desk:

SAM EATON: Scientists at the National Oceanic and Atmospheric Administration call the Carbon Tracker the ultimate accounting tool for monitoring whether governments and industries are actually cutting back their greenhouse gas emissions.

The Carbon Tracker uses a series of sampling stations to pinpoint CO2 emissions on a city-by-city basis.

NOAA’s Richard Spinrad says the data will show whether local climate controls are actually paying off.

RICHARD SPINRAD: The environmental observations are irrefutable. When you come right down to it that’s what’s going to provide the evidence, the foundation, the decision basis for determining what’s working and what’s not.

The economic stakes couldn’t be higher. Reductions in CO2 emissions have become a tradable commodity to the tune of tens of billions of dollars.

NOAA hopes to expand its Carbon Tracker globally.

It’s also developing a method to tell the difference between naturally occurring CO2 and that produced by burning fossil fuels.

I’m Sam Eaton for Marketplace.