to radiative forcings. They also found that the specification of observed sea surface temperature changes improves the reproduction of the vertical structure of temperature changes. The latter finding is consistent with other studies indicating that SSTs contain additional information (related perhaps to dynamical changes in the climate associated, for example, with ENSO or the annular modes) with regard to the patterns of response to forcing not necessarily produced by the atmospheric response to radiative forcing changes alone (Folland et al., 1998; Sexton et al., 2003).
During the past 25 years, the stratosphere has witnessed significant climate change (Ramaswamy et al., 2001; Shine et al., 2003; Ramaswamy and Schwarzkopf, 2002; Schwarzkopf and Ramaswamy, 2002). Indeed, the temperature at 1 mb has dropped significantly over the past two decades. Models are able to explain the cooling of the lower stratosphere in terms of stratospheric ozone loss; upper stratosphere cooling is due to a combination of ozone change and greenhouse gas increases.