Recent work (e.g., Hurrell 1995, 1996; Thompson and Wallace 1998; Corti et al., 1999) has suggested that the observed warming
over the
last few decades may be manifest as a change in
frequency of these naturally preferred patterns (Chapters 2 and 7) and there is now considerable interest in testing the ability of climate models to simulate such weather regimes (Chapter 8) and to see whether the greenhouse gas forced runs suggest shifts in the residence time or transitions between such regimes on long time - scales.