Geography Reference
In-Depth Information
over the Russian sector of the Arctic and least over parts of the
North Atlantic. Winters are likely to be affected much more
than summers, while precipitation changes are likely to be more
variable.
Physical geographers play an important role in testing the
General Circulation Models (GCMs) that simulate the Earth's
climate system and predict the likely course of future climate.
While few geographers have the physical and mathematical skills
to design GCMs, they are widely involved in the multidisciplinary
effort to test these models using our knowledge of past climates.
Because GCMs are predicting the future, they cannot be tested
by conventional observation and experiment: but they can be
tested by seeing whether they are able to predict what has
already happened. This is why reconstructions of past climates
by physical geographers and others are so important. Such
palaeo-climatic reconstructions are made using evidence
from many different sources (such as ice cores, peat bogs,
lake sediments, and tree rings) collected from many different
environments. The accuracy with which the models can predict
palaeo-climates that differ from present-day climates provides a
measure of the confi dence we can have in their ability to predict
future climatic conditions.
The impacts of global warming also vary in different parts of the
world. Natural environmental systems differ in their sensitivity
to rising temperatures, as do human systems. An example of a
highly sensitive natural system is provided by the African Sahel,
where relatively small changes in annual or seasonal temperature
can greatly infl uence moisture availability, vegetation growth,
and dependent cropping and grazing economies. Regions with
lower temperatures and/or more frequent rains provide a starting
point that is less vulnerable to drought. A very different example
is provided by the impact of rising temperatures on the glacial
and periglacial environments in the European Alps. There,
warming has led to rapidly diminishing glaciers, an increase in
