Is the tropopause a sensitive indicator of climate change?

Recent work by Sausen and Santer (Meteorol. Zeitschrift 2003) and Santer et al. (Science 2003, J. Geophys. Res. 2003) suggests that changes in the height (or pressure) of the global tropopause may be a sensitive indicator of anthropogenic climate change. These studies employed NCEP/NCAR and ECMWF reanalysis data and climate model simulations, in which tropopause height increases were closely associated with tropospheric warming and stratospheric cooling.

We have examined radiosonde data from about 100 stations around the world for 1958-2004 to determine the relationships between tropopause height changes and changes in temperature throughout the troposphere and lower stratosphere (surface to 10 mb), on synoptic, seasonal, interannual, and multidecadal time scales. Preliminary results confirm that, for synoptic, interannual, and multidecadal time scales the local tropopause varies in the manner suggested by the studies cited above. However, seasonal variations are more complex and vary geographically. These results are complicated by the existence of multiple tropopauses, particularly in midlatitude winter jet stream regions. Long-term trends in tropopause heights, their relation to temperature trends, and the degree to which radiosonde data inhomogeneities contaminate tropopause trend estimate will also be reported.