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Atmospheric profiles in North America during the period 2010-2011, obtained from archived radiosonde measurements, were analysed in terms of changes in molar density (D) with pressure (P). This revealed a pronounced phase change at the tropopause. The air above the tropopause (i.e., in the tropopause/stratosphere) adopted a “heavy phase”, distinct from the conventional “light phase” found in the troposphere. This heavy phase was also found in the lower troposphere for cold, Arctic winter radiosondes.
Reasonable fits for the complete barometric temperature profiles of all the considered radiosondes could be obtained by just accounting for these phase changes and for changes in humidity. This suggests that the well-known changes in temperature lapse rates associated with the tropopause/stratosphere regions are related to the phase change, and not “ozone heating”, which had been the previous explanation.
Possible correlations between solar ultraviolet variability and climate change have previously been explained in terms of changes in ozone heating influencing stratospheric weather. These explanations may have to be revisited, but the correlations may still be valid, e.g., if it transpires that solar variability influences the formation of the heavy phase, or if the changes in incoming ultraviolet radiation are redistributed throughout the atmosphere, after absorption in the stratosphere.
The fits for the barometric temperature profiles did not require any consideration of the composition of atmospheric trace gases, such as carbon dioxide, oxone or methane. This contradicts the predictions of current atmospheric models, which assume the temperature profiles are strongly influenced by greenhouse gas concentrations. This suggests that the greenhouse effect plays a much smaller role in barometric temperature profiles than previously assumed.
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