Investigating the Paleo Carbon Monoxide Budget
Chemical and photo-chemical processes in the atmosphere control the lifetimes of most atmospheric trace species (e.g., methane, aerosols, ozone-destroying CFCs) and have a profound influence on the Earth’s climate system. Current understanding of atmospheric chemistry is imperfect, and state-of-the-art models need realistic training data sets that describe atmospheric conditions that are very different from today’s, such as the pre-industrial atmosphere.
One aspect of our research focuses on reconstructing past concentrations and stable isotopic composition of carbon monoxide (CO). CO is a reactive trace gas that plays a key role in atmospheric chemistry by being the main sink of tropospheric hydroxyl radicals (OH). OH is the main atmospheric oxidant and is responsible for removal of most atmospheric trace species. Because of its strong interaction with OH, CO is a must-have component of any data set that attempts to fully characterize the chemical state of the atmosphere. Our recent work succeeded for the first time in providing a reliable record of CO concentrations for the last 60 years for the Northern Hemisphere. Our reconstructions showed that CO was actually slightly higher in the Northern Hemisphere in 1950 than it is today. CO peaked around 1980, with a subsequent strong decrease. This CO trend was driven mainly by CO emissions from fossil fuel combustion, and the large post-1980 CO decrease was driven by the widespread introduction of catalytic converters in road transportation. Our CO reconstruction was in strong disagreement with predictions from a state-of-the-art climate-chemistry model, pointing out important errors in the modeling work.
We are continuing our work on past CO in the Northern Hemisphere, with the hope of extending the CO concentration and stable isotope records to ≈1750 AD, before the start of the Industrial Period. We are also studying CO in in Antarctic ice with the aim to explore CO changes in the natural atmosphere as far back in time as 20,000 years.
This research direction is being supported by NSF Polar awards ARC-1406236 and PLR-1443267, as well as by the Packard Foundation.
Helmig, D., V.V. Petrenko, P. Martinerie, E. Witrant, T. Roeckmann, A. Zuiderweg, R. Holzinger, J. Hueber, C. Stephens, J. White, W. Sturges, A. Baker, T. Blunier, D. Etheridge, M. Rubino and P. Tans. 2014. Reconstruction of Northern Hemisphere 1950 – 2010 atmospheric non-methane hydrocarbons. Atmospheric Chemistry and Physics,14, 1463–1483. http://www.atmos-chem-phys.net/14/1463/2014/
Petrenko, V.V., P. Martinerie, P. Novelli, D. M. Etheridge, I. Levin, Z. Wang, G. Petron, T. Blunier, J. Chappellaz, J. Kaiser, P. Lang, L. P. Steele, F. Vogel, M. A. Leist, J. Mak, R. L. Langenfelds, J. Schwander, J. P. Severinghaus, G. Forster, W. Sturges, M. Rubino, J.W.C. White. 2013. A 60 yr record of atmospheric carbon monoxide reconstructed from Greenland firn air. Atmospheric Chemistry and Physics, 13, 7567 - 7585. http://www.atmos-chem-phys.net/13/7567/2013/
Wang, Z., J. Chappellaz, P. Martinerie, K. Park, V.V. Petrenko, E. Witrant, T. Blunier, C. A. M. Brenninkmeijer, J. E. Mak. 2012. The isotopic record of Northern Hemisphere atmospheric carbon monoxide since 1950, implications for the CO budget. Atmospheric Chemistry and Physics, 12, 4365–4377. http://www.atmos-chem-phys.net/12/4365/2012/