Direct Impacts of Climate Change on Freshwater Ecosystems - Climate Change Impacts on Freshwater Ecosystems - page 43

(a) (b)

Increase in mean Increase in variance

Previous
climate

More
hot
weather

More
hot
weather

More
cold
weather

Previous
climate More

record
cold
weather

More
record hot
weather

More
record hot
weather

Less
cold
weather

New
climate New

climate

Cold Average Hot

Cold Average Hot

(c)

Increase in mean and variance

Much more
hot
weather

Previous
climate

More
record hot
weather

Less
change for
cold
weather

New
climate

Cold Average Hot

Figure 3.4 Schematic diagram showing the effect on extreme temperatures of (a) an
increase in mean temperature, (b) an increase in the variance and (c) an increase in both
mean temperature and variance for a normal distribution of temperature. (Modified from
Climate Change 2001: The Scientific Basis. Contribution of Working Group I to the Third
Assessment Report of the Intergovernmental Panel on Climate Change (eds J.T. Houghton,
Y. Ding, D.J. Griggs, et al .). Cambridge University Press, Cambridge and New York.)

Summer

σ = 0.94°C
T '/

σ = 5.4

10 12 14 16

Temperature (°C)

18 20 22 24 26

Figure 3.5 Distribution of Swiss summer temperatures (June-August) for 1864-2003.
(From Climate Change 2007: The Physical Science Basis. Contribution of Working Group I
to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change
(eds S. Solomon, D. Qin, M. Manning, et al .). Cambridge University Press, Cambridge
and New York after Schär et al . 2004.)

In winter, extreme daily precipitation events are very likely to increase in
both magnitude and frequency in the northern parts of Europe, with a larger
relative change in frequency than in magnitude (e.g. Räisänen 2005). In summer,
too, extreme daily precipitation is projected to increase despite decreasing mean