Sherwood, S.C, C. L. Meyer and R. J. Allen, Robust tropospheric warming revealed by iteratively homogenized radiosonde data. Submitted to J. Climate, 11/07.

Results are presented from a new homogenization of data since 1959 from 527 radiosonde stations. This effort differs from previous ones by employing an approach specifically designed to minimize systematic errors in adjustment, by including wind shear as well as temperature, by seasonally resolving adjustments, and by using neither satellite information nor station metadata. Relatively few artifacts were detected in wind shear and associated adjustments were indistinguishable from random. Temperature artifacts were detected most often in the late 1980's-early 1990's. The meridional variations of zonally aggregated temperature trend since 1979 moved significantly closer to those of the MSU (Microwave Sounding Unit) after data adjustment. From 5S-20N however the adjusted data continue to show evidence of inhomogenieities in the troposphere. Stratospheric cooling also remains stronger than indicated by MSU and likely excessive. Elsewhere, the adjusted trends are close to those of MSU for the lower troposphere (TLT), and for Channel 2 are closest to those analyses (Remote Sensing Systems and the University of Maryland) showing the strongest warming. The troposphere warms at least as strongly as the surface, with local warming maxima at 300 hPa in the Tropics and in the boundary layer of the extratropical northern hemisphere (ENH). Tropospheric warming since 1959 is almost hemispherically symmetric, but since 1979 is significantly stronger in ENH and weaker in ESH (extratropical southern hemisphere). ESH trends are relatively uncertain due to poor sampling. While this effort appears not to have detected all artifacts, trends appear to be systematically improved, and change more than in previous efforts. Several suggestions are made for future attempts. These results support the hypothesis that trends in wind data are relatively uncorrupted by artifacts compared to temperature, and should be exploited in future homogenization efforts.