Invited keynote address 

The aim of the symposium 

Gunter Weller, University of Alaska Fairbanks 
Chairman, Scientific Steering Committee 

The polar regions play a crucial role in global 
climate change. They are sensitive indicators of 
change and their snow and ice features are good 
integrators of change. They store long-term 
climatic records in their ice sheets, such as the 
Antarctic and Greenland ice sheets. They also 
affect the global climate directly through interac- 
tions between their atmospheres, ice cover, and 
oceans, and through feedback processes. Practi- 
cally all climate models predict an amplification of 
the global greenhouse effect at high latitudes, but 
models as well as observations have produced 
results that are not easily interpreted. 

There are large differences, for example, 
between the results of various GCM simulations, 
and uncertainties exist about the magnitude and 
timing of the expected changes. Also, the observed 
high latitude climate trends over the last few 
decades are much more regional and patchy than 
predicted by the models. Models are improving, 
however, with the introduction of sulphate aero- 
sols and the elimination of flux adjustments and 
while considerable uncertainties remain in the 
long-term prediction of change there is some 
agreement between model results and observed 
trends by season on shorter time scales. 

The warming observed over the landmasses of 
the Arctic and in the Arctic Ocean over the last few 
decades is matched by corresponding observed 
changes i n  the cryosphere, including decreases in 
snow cover and glacier mass balances. thawing of 
permafrost, and by reductions in sea ice extent and 
thickness. In Antarctica, warming in the Antarctic 
Peninsula and Ross Sea regions is associated with 
dramatic reductions in ice shelf areas and reduced 
ice thicknesses on the lakes in the McMurdo Dry 
Valleys. 

A warmer climate in future will accelerate 
permafrost thawing on land and thus affect 
ecosystems and humans, it will change the 
productivity of marine ecosystems in the Arctic 
and Southern oceans, will have economic impacts 
on fisheries, petroleum production and other 
human activities, and will cause social conse- 
quences on northern indigenous populations. 
While uncertainties exist about the future, climate 
change in the polar regions during the past few 
decades can be shown to have already had major 
impacts which will become much more pro- 
nounced if present trends continue. 

The key questions that need to be answered to 
remove some of the uncertainties include the 
following: 

Are we already seeing a climate change due to 
the greenhouse effect, as predicted by GCMs, 
and if not when are we likely to see it, and 
where? 
Are the changes in climate that we see $h the 
polar regions due to natural or man-’made 
causes, or both; and if both, what are their 
relative contributions to change? 

0 What parameters, processes and interactions - 
past, present and future - do we need to 
understand better in order to predict future 
climate change? 
What are the likely impacts of global change on 
the polar environment and people and of polar 
processes and feedbacks on the global climate 
and society? 

The aim of this symposium is to begin to answer at 
least some of these questions. 

Weller 1999: Polar Research 18(2), 115 115