Their models are full of guesses and now we hear that one such lot of guesses was quite wrong. Journal abstract follows:
Boundary Layer Halogens in Coastal Antarctica
By Alfonso Saiz-Lopez et al.
Halogens influence the oxidizing capacity of Earth's troposphere, and iodine oxides form ultrafine aerosols, which may have an impact on climate. We report year-round measurements of boundary layer iodine oxide and bromine oxide at the near-coastal site of Halley Station, Antarctica. Surprisingly, both species are present throughout the sunlit period and exhibit similar seasonal cycles and concentrations. The springtime peak of iodine oxide (20 parts per trillion) is the highest concentration recorded anywhere in the atmosphere. These levels of halogens cause substantial ozone depletion, as well as the rapid oxidation of dimethyl sulfide and mercury in the Antarctic boundary layer.
Science 20 July 2007: Vol. 317. no. 5836, pp. 348 - 351
Another summary of the above paper:
Tropospheric halogens affect the concentration of ozone, the oxidizing capacity of the atmosphere, and aerosol formation, all of which are linked to climate. The halogen chemistry of the frozen high latitudes has proven to be particularly interesting, not least because of the role of these regions as harbingers of global climate change, but a better understanding of that chemistry has been hampered by lack of data. Saiz-Lopez et al. (p. 348) present measurements of BrO and IO in the Antarctic boundary layer from January 2004 to February 2005. They observed high concentrations and persistence of these halogens throughout the sunlit period, contrary to expectations and unlike the situation in the Arctic, where IO has not been detected. The springtime IO levels they found are the highest reported anywhere in the atmosphere, and an apparent synergy between IO and BrO suggests an unknown halogen-activation mechanism. These levels of halogens also cause the rapid oxidation of dimethyl sulfide and mercury in the Antarctic boundary layer.
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