Chapter 7
The impacts of climate change
The lasttwo chapters have detailed the climate change that we can
expect during the twenty-first century because of human activities in
terms of temperature and rainfall. To be useful to human communities,
these details need to be turned into descriptions of the impact of climate
change on human resources and activities. The questions to which we
want answers are: how much will sea level rise and what effect will that
have?; how much will water resources be affected?; what will be the
impact on agricultureand food supply?; will natural ecosystems suffer
damage and how will human health be affected? This chapter considers
these questions.^1
A complex network of changes
In outlining the character of the likely climate change in different regions
of the world, the lastchapter showed that it is likely to vary a great
deal from place to place. For instance, in some regions precipitation will
increase, in other regions it will decrease. Not only is there a large amount
of variability in the character of the likely change, there is also variability
in the sensitivity (for definition see box below) of different systems to
climate change. Different ecosystems, for instance, will respond very
differently to changes in temperature or precipitation.
There will be a few impacts of the likely climate change that will
be positive so far as humans are concerned. For instance, in parts of
Siberia or northern Canada increased temperature will tend to lengthen
the growing season with the possibility in these regions of growing
a greater variety of crops. In some places, increased carbon dioxide
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