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that cold (Fig. 5). Winter temperatures are on a scale from
around 5°C colder than RP in southern Europe to around
15°C colder in southern Scandinavia and more than 30°C
colder in the ice covered areas. In summer southern and
western Europe are 3-6°C colder and eastern Europe 0-3°C
colder than in the RP. Ice covered areas are around 15°C
colder than RP conditions. Around the Mediterranean Sea,
precipitation amounts are about the same as in the recent
past although with more precipitation in the southwest (not
shown). Most of central Europe gets 10-20 mm/month less
precipitation than today. The largest difference is over the
Norwegian Sea where the sea ice prevents evaporation and
thereby convection and precipitation.
3
0
−3
−6
−9
−12
−15
−18
−21
−24
−27
−30
−33
−36
−39
−42
−45
Figure 3. Mean temperature of the warmest month in
LGM as compared to recent past climate.
Corresponding temperatures as given by proxy based
reconstructions are denoted in the filled circles. Units
are ˚C.
42
36
30
24
18
12
6
0
−6
−12
−18
−24
−30
−36
−42
Figure 4. Mean temperature of the coldest month in
MIS 3. Corresponding temperatures as given by proxy
based reconstructions are denoted in the filled circles.
Units are ˚C.
Proxy data are sparse which limits any profound evaluation
of the model results. The single point of SST proxies at high
latitudes in the Atlantic is in better agreement with the
simulation than the corresponding agreement in LGM,
however the comparison of terrestrial proxies with the
regional climate model results shows that RCA3 is colder
than recorded at the three available sites in the British Isles
for the warmest month of the year (Fig. 5). This may
indicate that summertime SSTs in parts of the North
Atlantic are indeed too low. For all the other locations in
western Europe the agreement between simulation and
proxy data is reasonable and within the uncertainty ranges
assigned to the proxies.
42
36
30
24
18
12
6
0
−6
−12
−18
−24
−30
−36
−42
Figure 5. Mean temperature of the warmest month
in MIS 3. Corresponding temperatures as given by
proxy based reconstructions are denoted in the filled
circles. Units are ˚C.
4. Concluding remarks
RCA3 is able to reproduce climates very different from
today. The results are in broad agreement with available
proxy data and other climate model simulations. The
resulting climate is in a qualitative agreement with the
imposed extent of ice sheets and types of vegetation for
the respective climate case. In particular we show that the
results for the cold MIS 3 case are consistent with ice free
conditions in south-central Fennoscandia. The results of
the iterative simulations with the regional climate model
and the dynamic vegetation model show that this is indeed
a viable approach as the resulting vegetation is close to the
vegetation in the LGM as estimated by other models and
to the vegetation in MIS 3 as deduced from palaeo data.
5. Acknowledgements
This project was initiated by Svensk Kärnbränslehantering
AB (SKB). Joel Guiot, Masa Kageyama, Antje Voelker
and Barbara Wohlfarth kindly provided proxy data. This
research uses data provided by the Community Climate
System Model project supported by the Directorate for
Geosciences of the National Science Foundation and the
Office of Biological and Environmental Research of the
U.S. Department of Energy. All model simulations with
the global and regional climate models were performed on
the climate computing resource Tornado operated by the
National Supercomputer Centre at Linköping University.
Tornado is funded with a grant from the Knut and Alice
Wallenberg foundation.
References
Kjellström, E., Brandefelt, J., Näslund, J-O., Smith, B.,
Strandberg G., Wohlfart, B., Climate conditions in
Sweden in a 100,000-year time perspective, Svensk
Kärnbränslehantering AB, report TR-09-04, pp. 128,
2009