The overall impactof global warming 187warming, although large, at a few per cent of GWP are not imposs-
ibly large, and that we might be able to buy our way out of the problems
of its impact. There are, however, two factors which have been omitted
from the studies cited above. The first is that the studies have only been
concerned with the impacts of global warming up to about the middle
of the next century when, for a business-as-usual scenario, the equi-
valent carbon dioxide concentration will have doubled from its pre-
industrial value. The longer-term impacts, if the growth of greenhouse
gases continues under business-as-usual, are likely to be much greater.^68
The second factor is that impacts cannot be quantified in terms of mon-
etary cost alone. For instance, the loss of life (see question 7), human
amenity, natural amenity or the loss of species cannot be easily expressed
in money terms. This can be illustrated by focusing on thosewho are
likely to be particularly disadvantaged by global warming. Most of them
will be in the developing world at around the subsistence level. They
will find their land is no longer able to sustain them becauseit has been
lost either to sea level rise or to extended drought. They will therefore
wish to migrate and will become environmental refugees.
It has been estimated that, under a business-as-usual scenario, the to-
tal number of persons displaced by the impacts of global warming could
total of the order of 150 million by the year 2050 (or about three million
per year on average) – about 100 million due to sealevel rise and coastal
flooding and about fifty million due to the dislocation of agricultural pro-
duction mainly due to the incidence and location of areas of drought.^69
The cost of resettling three million displaced persons per year (assuming
that is possible) has been estimated at between $US1000 and $US5000
per person, giving a total of about ten thousand million US dollars per
year.^70 What the estimated cost for resettlement does not include, how-
ever (as the authors of the study themselves emphasise), is the human
cost associated with displacement. Nor does it include the social and po-
liticalinstabilities that ensue when substantial populations are seriously
disrupted because their means of livelihood has disappeared. The effects
of these could be very large.
The overall impact of global warming
The incidence of various impacts of global warming is complex and far
from uniform over the world. The following is a brief summary of what
we have learnt in this chapter.
There are many ways in which our current environment is being de-
graded due to human activities; global warming will tend to exacerbate
these degradations. Sea level rise will make the situation worse for