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Counting Carbon

Collide-a-ScapeBy Keith KloorMarch 2, 2011 3:30 AM


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Ever wonder how scientists can determine how much carbon dioxide (CO2) is accumulating in the atmosphere? In this engaging story, science writer Tom Yulsman visits a CO2 monitoring station high up in the Colorado mountains and brings a crucial part of climate science down to earth. Here's the scene and a snippet of how the data is collected and analyzed:

From a two-room structure in a clearing on the forested slopes of Niwot Ridge, [NOAA's Duane] Kitzis regularly fills cylinders with ambient air. Then he hauls them back down the mountain to a NOAA lab where infrared analyzers are used to determine with exquisite precision the air's chemical composition. These samples are then sent out to the global network of monitoring sites. Since the makeup of each one has been determined to very fine precision, the different groups can use them to verify that their own instruments are providing accurate readings. In this way, the air Kitzis captures and analyzes is used as the "standard" against which other samples are compared, enabling atmospheric monitoring of CO2 concentrations around the world to be done precisely and in coordination. I am an empiricist," Kitzis says. "I like instruments and measuring things." But how can Kitzis and his colleagues make sure that everything is kosher in their own lab? Here, the system gets even more complicated, with multiple internal calibrations involving two different sets of cylinders, some of which were collected on Niwot Ridge 25 years ago. (For the gory details, see this publication from NOAA.) Thanks to these meticulous efforts, there is no scientific doubt about what is happening to the atmosphere. "We are very certain about the increase in CO2," [NOAA's Pieter] Tans says. "In fact, it is the thing that is most certain in our knowledge about climate change.

As someone who once sent Yulsman out to report similar stories (here is one of my favorites), I can tell you that he's got a knack for distilling the science conducted at high elevations. So go have a look at his latest.

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