Climate Change and the European Water Dimension - Agri ...

of methods for rainfall point and spatial measurement, estimates, prediction and
modeling see Smith (1993).
Precipitation and climate change
Annual precipitation trends in the 20 th century included enhanced precipitation (10 to
50%) in the northern half of Europe. By contrast, the region stretching from the
Mediterranean Sea through central Europe into the European part of the Russian
Federation and Ukraine experienced decreases in precipitation by as much as 20%
in some areas (Figure III.3).
Figure III.3. Annual precipitation trends in Europe for the period 1900-1999. Black
represents an increase; white represents a decrease (EEA, 2004).
Predictions of climate change are subject to large uncertainty. Changes in global
precipitations are influenced by changes in global mean temperatures. Even where
the likely global trend appears to be clear, the response in individual regions may
vary substantially. Thus, although global temperatures are predicted to increase by 1
to 3.5 °C by the year 2100 (Nicholls et al., 1996) the actual rise in individual areas will
differ significantly, and some regions may even become cooler. Increasing
temperatures mean also that a smaller proportion of precipitation may fall as snow. In
areas where snowfall currently is marginal, snow may cease to occur altogether, with
significant implications for hydrological regimes (e.g. spring river flows where
snowmelt plays a significant role).
Global average precipitation is predicted to rise, but this increase is also likely to be
regional. It is predicted that winter and spring precipitation will increase in Europe
and summer precipitation will decrease, although the Mediterranean region and
central and eastern Europe are expected to experience overall reduced precipitation
(Kovats et al., 2000; see also Figure III.4). Recent scenarios for the UK, derived from
HadCM2 experiments, indicate an increase in the relative variability of seasonal and
annual rainfall totals resulting from global warming (Hulme and Jenkins, 1998).
Although global mean precipitation is primarily constrained by the energy budget, the
heaviest rainfalls are likely to occur when effectively all the moisture in a volume of
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