Environmental Engineering Reference
In-Depth Information
Figure 24.7
The highly fluctuating populations of lynx and
snowshoe hare in the Canadian Arctic as illustrated by
figures for skins traded by the Hudson's Bay Company,
1845-1935.
Source: Hudson's Bay Company records.
snowy owls and gyrfalcons, whose numbers fluctuate in sympathy. Population cycles
have also been noted in caribou and walrus, and are likely to be more common than is
realized, given that there are not many long-term
POLAR CLIMATES, GLOBAL WARMING AND POLAR ICE SHEETS
new developments
There has been much debate over the future climates of the north polar and south polar
regions with global warming. Although predicting climatic change is full of doubts and
uncertainties, it is an important science, as climatic change will have major effects on the
economy and ecology of the entire Earth. In particular the questions being asked are:
what would happen if the Antarctic and Greenland ice sheets were to collapse into the
ocean? What would be the amount and speed of the inevitable rise of sea level?
Predictions are reached by a combination of field observations and constructing computer
models of climate (global climate models or GCMs). There are many lines of evidence in
the first category, from research on the temperature and gas content in ice cores taken
from ice sheets and from permafrost to studies of the mass budgets of the ice sheets
themselves. Cores taken from marine sediments close to ice shelves, where, for example,
the skeletons of marine organisms can accumulate, indicate past water temperatures.
Given the large number of complex relations which make up the climate system, it is
hardly surprising that different GCMs give different results for global warming.
Uncertainty is compounded as some of the main relations are to an external factor,
namely the sun; in addition, many linkages in the climate system are indirect, non-linear
and subject to unpredictable time lags.
The Intergovernmental Panel on Climatic Change (IPCC) notes the rise in average
global temperatures of between +0·5° C and + 0·6° C from 1860 to the present, and a
predicted rise of between + 0·3° C and + 0·5° C from 2000 to 2100. However much
GCMs may differ from one model to another, they all predict that global warming will
not be uniform over Earth, but will be greater at high latitudes, compared with mid and
low latitudes. Some models predict that warming will be equal at both poles, but most
predict that warming in the Arctic will be significantly greater than in the Antarctic
