Aug. 1, 2013
Curtailing emissions of a common non-greenhouse gas can improve air quality regionally in the near term and contribute globally to the reduction of two detrimental greenhouse gases.

A new study led by Meridith Fry, PhD, recent alumna of the Gillings School of Global Public Health’s Department of Environmental Sciences and Engineering, examines the role of carbon monoxide (CO), a byproduct of the incomplete combustion of carbon fuels, in climate change.

The study, “Net radiative forcing and air quality responses to regional CO emission reductions,” was published May 29 in the journal Atmospheric Chemistry and Physics.

Carbon monoxide does not directly contribute to global climate change, but it does react in the atmosphere to produce methane and ozone.  Methane and ozone follow only carbon dioxide in their contributions to human-caused climate change. Despite this, carbon monoxide was not identified among the suite of greenhouse gases addressed by the Kyoto Protocol or most other international agreements aimed at reducing climate change.
“Carbon monoxide is really Kyoto’s forgotten gas when it comes to climate change efforts and agreements,” said Jason West, PhD, assistant professor of environmental sciences and engineering at the Gillings School and a co-author of the study.

Carbon monoxide has not been targeted as a greenhouse gas in part because its effects on climate depend upon the locations from which it is emitted.

“That complexity does not apply to other greenhouse gases, such as carbon dioxide,” West said. “In terms of climate, it doesn’t matter where carbon dioxide is emitted. This study shows for the first time that while the climate forcing of carbon monoxide varies with the location of emissions around the world, it only varies by a small amount. That may help justify including the gas in international agreements.”   

“Climate forcing” is an indicator that measures the heating effect caused by greenhouse gases in the atmosphere.  For human-caused climate change, the authors estimate that emissions of carbon monoxide cause about 8 percent of the climate forcing of carbon dioxide. 

Fry says the study presents an important incentive for countries to lower carbon monoxide emissions. Reduction of ozone would improve human health in the near-term, and the reduction of methane and ozone would mitigate climate change.

“Ozone has been implicated in respiratory and cardiovascular illnesses, and carbon monoxide also affects health,” Fry said. “If a country reduces its carbon monoxide emissions, it would improve its own air quality and the health of its population within months.”

West added that reductions could be made in more developed nations by adopting stricter emissions standards for new vehicles and expanding reliance on mass transit. In less developed nations, emphasis could be placed upon improvements to inefficient industrial furnaces and residential stoves, and on reducing deforestation by burning.

“The effect of CO on climate is small, but it should not be forgotten,” West said.  “Including CO in a climate treaty can give countries incentive to reduce it, perhaps addressing climate change more cost-effectively.  Countries are likely to see the near-term local benefits for air quality and health as a good motivation to take action.”


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