Lisø PhD Dissertation Manuscript - NTNU

4 CLIMATE CHANGE SCENARIOS FOR
NORWAY
Scenarios regarding the climate development under
global warming have been studied worldwide. The
most realistic scenarios for changes in global climate
are based on Atmosphere-Ocean General Circulation
Models, AOGCM’s (IPCC 2001). The spatial resolution
in the recent AOGCMs is still too coarse to
enable these models to reproduce the climate on regional
or local scale. To deduce detailed scenarios
for future climate development in different parts of
Norway, both dynamic and empirical downscaling
techniques have been applied on an integration
(“GSDIO”) with the Max-Planck Institute’s global
climate model ECHAM4/OPYC3. This is a transient
integration up to year 2050, including greenhouse
gases, tropospheric ozone, and direct as well as indirect
sulphur aerosol forcings (Roeckner at al. 1999).
In this integration, the concentration of greenhouse
gases have been specified according to the IPCC
IS92a scenario, with an annual 1% increase in CO2
from 1990, giving a near doubling in concentration
in 2050. The downscaled scenarios for Norway include
climate elements such as temperature (2 m
level), precipitation (solid and liquid amounts), relative
humidity, solar radiation, wind speed, wave
height, sea level, etc. Most elements are given with a
time resolution down to 6 hours.
The empirical downscaled temperature scenarios
(Hanssen-Bauer et al. 2000) indicate average annual
warming rates of 0.2 to 0.5°C per decade up to year
2050 at the Norwegian mainland, and 0.6°C on
Svalbard. The warming rates are generally smallest
in southern Norway along the west coast. They increase
when moving inland and northwards. At the
west coast in southern Norway, the modelled warming
rates are rather similar in all seasons (0.2-0.3°C
per decade). Further north and in the inland region,
considerably larger warming rates are found for winter
than for summer. In northern Norway and inland
valleys in southern Norway, winter warming rates of
more than 0.5°C per decade are projected. Temperature
scenarios for some Norwegian sites are presented
in Table 1.
Table 1 also presents precipitation scenarios, deduced
by empirical downscaling (Hanssen-Bauer et
al. 2001). The scenarios indicate an increase in the
average annual precipitation in Norway of 0.3 to
2.7% per decade during the next 50 years. The projected
increase rates are generally smallest in southeastern
Norway, and largest along the northwestern
and western coast. In winter positive trends (1.8 to
3.2% per decade) are found all over the country.
Also in autumn the precipitation increase (0.6 to
5.9% per decade) at most places, with the largest in-
crease in western and northwestern regions. Modelled
spring precipitation tends to decrease in southern
Norway and increase in northern Norway, while
the summer precipitation tends to decrease in eastern
areas and increase in western areas.
Table 1. Empirically downscaled scenarios for changes in temperature
and precipitation. The values are based upon the differences
between the periods 1961-1990 and 2020-2049, and
are given as changes per decade. (Winter = Dec-Feb, summer =
J un-Aug).
Location Temperature change Precipitation change
(°C/decade) (mm/decade)
W* S* A* W* S* A*
Lillehammer 0.40 0.29 0.32 2.8 -2.6 2.0
Oslo 0.37 0.26 0.30 3.8 -2.8 2.3
Oksøy 0.32 0.22 0.25 8.2 -3.1 6.8
Stavanger 0.33 0.27 0.29 7.7 0.3 20.7
Bergen 0.28 0.28 0.28 18.5 8.0 56.3
Trondheim 0.34 0.25 0.27 4.8 2.1 20.4
Bodø 0.43 0.36 0.41 5.0 -0.7 27.5
Tromsø 0.48 0.28 0.39 5.9 -0.6 29.2
Karasjok 0.79 0.33 0.51 0.9 0.3 5.1
*W = Winter, S = Summer, A = Annual
Table 2. Dynamically downscaled scenarios for changes (%) in
frequencies of wind speeds above 15 m/s, six-hourly precipitation
intensities above 10 mm, and six-hourly snowfalls exceeding
5 mm water equivalent. The values are based on differences
in 6-hourly frequencies between the periods 1980-1999
and 2030-2049 for a limited number of grid points in each re-
g ion (from Haugen & Debenard, 2002).
Region Wind
speed
> 15 m/s
Oslo area
Western Norway
(coast)
North-western
Norway (coast)
Mountain regions,
S. Norway
Nordland (coast)
Troms, West-
Finnmark (coast)
East-Finnmark
(coast)
Precipitation
>10mm/6h
Snowfall
>5mm/6h
0 27 7
10 41 -27
11 24 -25
0 33 8
18 11 -20
28 25 -11
41 50 33
Dynamically downscaled scenarios for changes in
wind conditions (Haugen & Nordeng 2001) show a
zone with increased mean annual wind speed from
south of Iceland eastwards towards Fennoscandia.
For Norway the changes in annual wind speed are
small, with largest increase (~3%) in coastal areas in
Western Norway, and along the coast of Finnmark
county. High wind speeds are connected to the lowpressure
activity over Northern Europe, and an increased
frequency of wind speeds above 15 m/s is
found along the Norwegian coast (see Table 2). In