Scientists from the University of Rochester in New York say their first-ever study of air trapped in the deep snowpack of Greenland shows atmospheric levels of carbon monoxide in the 1950s were slightly higher than what exists today.
Earth and environmental sciences Professor Vasilii Petrenko says the study showed CO levels rose slightly from 1950 until the 1970s, and then declined significantly to present-day values.
"The CO decline coincides with improvements in combustion technology, in particular the introduction of catalytic converters in automobiles," Petrenko said. "CO emissions were declining even as fossil fuel use was increasing."
Carbon monoxide is a byproduct of combustion that can be deadly in high concentrations, although it exists in Earth's atmosphere in very low levels.
While not a greenhouse gas like carbon dioxide, the researchers noted, it plays an important role in atmospheric chemistry and an indirect role in global warming.
The Greenland study provided a CO history for the last 60 years that shows levels have been declining since the 1970s, despite a global increase in the number of vehicles being driven, they said.
"In order for computer models to get things right, it's important to have accurate historical records," Petrenko said. "Until now, we haven't had enough reliable data on carbon monoxide concentrations. This work helps to fill that gap."