Cooper, O.R., A. Stohl, M. Trainer, A.M. Thompson, J.C. Witte, S.J. Oltmans, G. Morris, K.E. Pickering, J.H. Crawford, G. Chen, R.C. Cohen, T.H. Bertram, P.J. Wooldridge, A.E. Perring, W.H. Brune, J. Merrill, J.L. Moody, D. Tarasick, P. Nédélec, G. Forbes, M.J. Newchurch, F.J. Schmidlin, B.J. Johnson S.Turquety, S.L. Baughcum, X. Ren, F.C. Fehsenfeld, J.F. Meagher, N. Spichtinger, C.C. Brown, S.A. McKeen, I.S. McDermid & T.Leblanc. 2006. Large upper tropospheric ozone enhancements above midlatitude North America during summer: In situ evidence from the IONS and MOZAIC ozone measurement network. Journal of Geophysical Research, 111, D24S05, doi:10.1029/2006JD007306.

Note: In 2007 this paper by CIRES scientist Owen Cooper and his colleagues (in the NOAA Earth System Research Laboratory and various other institutions) was selected for the NOAA's Office of Atmospheric Research (OAR) Outstanding Scientific Paper Award in the climate category. In the upper troposphere, ozone acts as a greenhouse gas. Cooper et al. found unexpectedly high levels of summertime ozone in the upper troposphere 10-11 km above eastern North America—these levels were not attributable to either the high amounts of ozone pollution at Earth’s surface or the higher ozone levels in the stratosphere. These enhancements can nearly double the amount of upper tropospheric ozone above the region. It was found that a natural factor—the emission of nitrogen oxides from lightning—acts in concert with the generally higher background levels of ozone precursor compounds in today’s polluted atmosphere to produce most of the upper-tropospheric ozone enhancement. This enhancement with a strong natural component contributes to the radiation budget on the regional scale, and is thus relevant to climate. (NB. CIRES = Cooperative Institute for Research in Environmental Sciences.)