Direct Impacts of Climate Change on Freshwater Ecosystems - Climate Change Impacts on Freshwater Ecosystems - page 39

0.6 14.6

0.4 14.4

0.2 14.2

0.0 14.0

-0.2 13.8

-0.4 13.6

-0.6 13.4

-0.8 13.2

1860 1880 1900 1920 1940 1960 1980 2000

Period
Years
25

Rate

C per decade

Annual mean

0.177 ± 0.052

Smoothed series
5%-95% decadal error bars

50
100
150

0.128 ± 0.026

0.074 ± 0.018
0.045 ± 0.012

Figure 3.1 Annual global mean surface temperature since 1850 showing linear trends over
the past 25 yr (yellow), 50 yr (orange), 100 yr (blue) and 150 yr (red). (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.)

Climate change
According to the IPCC Fourth Assessment Report (2007), global surface air
temperatures of the last few years (1995-2006, with the exception of 1996) are
among the 12 highest on record since 1850. Global average air temperature
increased by more than 0.7°C between 1906 and 2005, and decadal warming has
almost doubled over the past 50 years with an average value of 0.13°C per decade
(Fig. 3.1). Warming has been greater over land than over the oceans. Since 1979,
air temperature over land has risen, on average, by 0.27°C per decade (versus
0.13°C per decade over the oceans). The greatest warming has occurred at higher
northern latitudes, with mean arctic winter and spring surface air temperatures
having increased by approximately twice the global average, with strong decadal
fluctuations during the past 100 years. A similar trend has been found for what
Auer et al . (2007) call the Greater Alpine Region (the area between 4-19°E and
43-49°N), which has warmed twice as much as the global or northern hemispheric
mean since the late 19th century at all elevations.
Precipitation, though spatially and temporally highly variable, has also changed
significantly in many parts of the globe during the past 100 years with respect to
its amount, intensity, frequency and type. In Europe, average precipitation has