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The climate change in Europe simulated by the regional climate model
COSMO-CLM
Kai S. Radtke and Klaus Keuler
Brandenburg University of Technology, Environmental Meteorology, 03044 Cottbus, Germany, radtke@tu-cottbus.de
1. Introduction
A small ensemble of regional climate simulations (Hollweg
et al., 2008) was performed with the climate version (Böhm
et al., 2006) of the numerical weather prediction model
COSMO ('COnsortium for SMall scale Modelling', formerly
known as LM) (Steppeler et al., 2003). The COSMO-CLM
has been forced by output of the ECHAM5/MPIOM global
climate model, which contributed to the fourth climate
assessment report of the 'International Panel on Climate
Change' (IPCC, 2007). The simulations were performed by
the Model and Data group (M&D) of the Max Planck
Institute for Meteorology. The configuration of the model
was developed by the CLM Community (http://www.clmcommunity.eu/).
In this context, three realisations of the
climate of the 20th century (1961-2000) were simulated.
Each of the IPCC scenarios A1B and B2 (Nakiećenović,
2000) for the climate of the 21st century (2001-2100) was
simulated twice. The model grid has a resolution of 0.165°
and covers Europe nearly complete.
Here, the climate change signal and its variability with
regard to the different scenarios, the different realisations
and different time periods as well as regional and seasonal
differences are considered. Simulation results for the 2 m air
temperature and the precipitation sum are presented.
2. Temperature
The annual mean temperature for the climate of the 20th
century (1961-1990) amounts 280.77 K to 281.07 K for
Central Europe. Thus, the different realisations vary up to
0.3 K.
The 70-year climate change signals (2031-2060 vs. 1961-
1990) amount from 1.39 to 1.95 K for the A1B scenario
(figure 1) and from 0.84 to 1.30 K for B1. The variability is
caused by considering the different realisations. Six paired
comparisons between the two realisations of the future
climate and the three realisations of the climate of the 20th
century were taken into account for both scenarios. These
variability amounts to 0.56 K for the A1B scenario and to
0.46 K for B1, approximately 25-50% of the absolute value
of the simulated climate change. The warming is 0.55 to
0.65 K larger in the A1B scenario than in B1 for Central
Europe.
The annual cycle of temperature change for the A1B
scenario (figure 1) shows the strongest warming in summer
and winter and a moderate warming in spring. The B1
scenario feature a similar shape of the seasonal distribution
of climate change, but the warming is always lower.
The 100-year climate change signal (2061-2090 vs. 1961-
1990) is more intense than the 70-year signal, but it shows
for both scenarios a similar structure. The warming for
Central Europe amounts from 2.81 to 3.19 K in the A1B
scenario and from 1.79 to 2.13 K in the B1 scenario. The
shape of the annual cycle of the climate change is similar to
the 70-year signal, but the values are larger. For the B1
scenario, this increase in time is somewhat lower.
The simulated warming is in southern, southwest and
northern Europe relative strong, but in Central Europe more
moderate. The increase in annual mean temperature for
northern Europe (A1B, 70-year: 1.8 to 2.2 K for
Scandinavia) and southern Europe (1.8 to 1.9 K for the
Iberian Peninsula) has a similar magnitude. But the
seasonal trends of global warming are completely
different. The warming in southern Europe is strongest in
summer. In contrast, it is strongest in winter time in
northern Europe. This fact is characteristic for both
scenarios.
2,5
1,5
0,5
-0,5
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Figure 1. The 70-year climate change (2031-2060
vs. 1961-1990) for the near surface temperatures for
Central Europe for the scenario A1B in K. Six
paired comparisons (A1B (realisation 1) minus
climate of the 20-th century (realisation 1 to 3) and
the same for A1B (realisation 2)) are given for any
month. The line shows the average of all paired
comparisons.
3. Precipitation
The 30-year averages of annual precipitation sums vary
for the climate of the 20th Century from 1021 to 1036 mm
for Central Europe. The 70-year climate change signal
amounts from 4 to 21 mm for A1B, from -17 to 34 mm for
B1. So, the change of the precipitation in Central Europe
is low (the largest value is lesser than 5% of the total
precipitation amount). The variability of the simulated
climate change for the different paired comparisons is
relatively large. Increases as well as decreases are
simulated. Thus, the simulations show no reliable change
of the annual precipitation sum for Central Europe. But
they feature a shift of precipitation from summer to winter.
This shift is more clearly developed in the 100-year
climate change signal (figure 2). Furthermore, it's stronger
in the A1B scenario. The 100-year time period also does
not show a reliable climate change for the annual
precipitation sum for both scenarios for Central Europe.
The changes amount from -16 to 12 mm for the A1B
scenario and from -2.5 to 18 mm for the B1 scenario.
Central Europe is in the transition zone between two
domains in Europe. An increase of annual precipitation is
simulated in the area of northern Europe (A1B, 70-year:
41 to 97 mm for Scandinavia). It's strongest in the winter.
But, the model produces a decrease in annual precipitation
for south and southwest Europe (-145 to +2 mm for the
Iberian Peninsula). This decrease is mainly caused by the
summer months. Both scenarios show that spatial pattern.