An international team of scientists has reconstructed a historic record of the atmospheric trace gas carbon monoxide by measuring air in polar ice and air collected at an Antarctic research station.
The team, led by the French National Centre for Scientific Research (CNRS) and Australia’s national science agency, CSIRO, assembled the first complete record of carbon monoxide concentrations in the southern hemisphere, based on measurements of air.
The findings are published in the journal Climate of the Past.
The record spans the last three millennia. CSIRO atmospheric scientist Dr. David Etheridge said that the record provides a rare positive story in the context of climate change.
“Atmospheric carbon monoxide started climbing from its natural background level around the time of the industrial revolution, accelerating in the mid-1900s and peaking in the early-mid 1980s,” Dr. Etheridge said.
“The good news is that levels of the trace gas are now stable or even trending down and have been since the late 1980s—coinciding with the introduction of catalytic converters in cars.”
Carbon monoxide is a reactive gas that has important indirect effects on global warming. It reacts with hydroxyl (OH) radicals in the atmosphere, reducing their abundance. Hydroxyl acts as a natural “detergent” for the removal of other gases contributing to climate change, including methane. Carbon monoxide also influences the levels of ozone in the lower atmosphere. Ozone is a greenhouse gas.
The authors have high confidence that a major cause of the late 1980s-decline was improved combustion technologies including the introduction of catalytic converters, an exhaust systems device used in vehicles.
“The stabilization of carbon monoxide concentrations since the 1980s is a fantastic example of the role that science and technology can play in helping us understand a problem and help address it,” Dr. Etheridge said.
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“Because carbon monoxide is a reactive gas, it is difficult to measure long term trends because it is unstable in many air sample containers. Cold and clean polar ice however preserves carbon monoxide concentrations for millennia,” Dr. Etheridge said.
The CO data will be used to improve Earth systems models. This will primarily enable scientists to understand the effects that future emissions of CO and other gases (such as hydrogen) will have on pollution levels and climate as the global energy mix changes into the future.
More information: Xavier Faïn et al, Southern Hemisphere atmospheric history of carbon monoxide over the late Holocene reconstructed from multiple Antarctic ice archives, Climate of the Past (2023). DOI: 10.5194/cp-19-2287-2023
Robin Edgar
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