Figure 9.30: Storm track
activity averaged over north-west Europe (6°W to 20°E, 40° to 70°N)
in the ECHAM4/OPYC greenhouse gas scenario run (Unit: gpm). A 4-year running mean
is shown for smoother display. The grey band indicates the variability of this
index in the control run as measured by one standard deviation. The non-linear
climate trend optimally obtained from quadratic curve fitting is marked by the
dashed line; y-axis is activity in gpm (geopotential metres) and x-axis is time
in calendar years. From Ulbrich and Christoph (1999).