132 Climate changein the twenty-firstcenturyand beyondFigure 6.9Daily rainfall for
Italy for a three-year period
simulated by a climate model,
(a) for the current climate
situation and (b) for the
climate if the equivalent
carbon dioxide concentration
increased by a factor of four
from its pre-industrial value
(predicted for instance to
occur before 2100 under the
A2 scenario).
ocean surfaceand which condenses in the clouds within the storm, re-
leasing energy. It might be expected that warmer sea temperatures would
mean more energy release, leading to more frequent and intense storms.
However, ocean temperature is not the only parameter controlling the
genesis of tropical storms; the nature of the overall atmospheric flow is
also important. Further, although based on limited data, observed vari-
ations in the intensity and frequency of tropical cyclones show no clear
trends in the last half of the twentieth century. Models can take all the
relevant factors into account but, because of the relatively large size
of their grid, they are unable to simulate very reliably the detail of rela-
tively small disturbances such as tropical cyclones. There is no consistent