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Environment

Carbon Dioxide May Be the Least of Our Warming Worries

New studies show an even greater accumulation of other, potentially more potent greenhouse gases.

By Melinda WennerJanuary 25, 2009 6:00 AM

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When people think of climate change, they think of carbon dioxide. But while CO2 represents 77 percent of all man-made greenhouse gas emissions, its relative contribution may be declining. According to two studies published late last year, atmospheric levels of other, more potent gases that also affect climate are on the rise.

One such gas is nitrogen trifluoride (NF3), which is used to make retail items like microchips and flat-screen TVs. In a study published in Geophysical Research Letters, researchers analyzed air samples and found that atmospheric NF3 seems to be growing by 11 percent each year across the globe. NF3 lingers in the air for 550 years, on average, and is 17,000 times better at trapping heat than CO2 on a molecule-per-molecule basis. Today the effect of NF3 on climate is just 0.04 percent that of carbon dioxide, but its role could grow dramatically if more manufacturers start using it, says study author Ray Weiss, a geochemist at the Scripps Institution of Oceanography. NF3 emissions are not currently regulated by any government.

A more immediate problem for climate change is methane, which is released by landfills and melting perma­frost and through farming practices. Levels of this gas are increasing today after eight years of stasis, according to another study in Geophysical Research Letters. Methane remains in the atmosphere one-tenth as long as CO2—about a decade—but traps 20 times as much heat.

No one yet knows the extent to which methane and NF3 will impact global temperatures, but NASA climate scientist Ralph Kahn says one thing is certain: “We know it’s more than just CO2 that matters.” His colleague James Crawford adds, “There’s going to be a lot more looking at this, trying to understand what is going on.”

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