Geography Reference
In-Depth Information
2
Global warming
Keith Boucher
THE NATURE OF THE PROBLEM
FIELD OF STUDY AND RELEVANT
LITERATURE
The greenhouse effect
The 'natural' greenhouse effect occurs because
some of the gases present in the atmosphere are
largely transparent to incoming solar radiation but
not to outgoing radiation, which is partially
absorbed by water vapour, and the three main
greenhouse gases. Their current percentage
contributions are 70 per cent for carbon dioxide,
23 per cent for methane and 7 per cent for nitrous
oxide. Water vapour is very variable in time and
space. CFCs (chlorofluorocarbons) and their
interaction with the variable greenhouse gas,
ozone, also need to be noted as potential
contributors (IPCC 1990). These gases are
collectively known as 'the greenhouse gases'. The
additional amount of such gases that are present in
the atmosphere as a direct or indirect result of
human activity, such as power generation and
vehicle emissions, leads to an 'enhanced'
greenhouse effect.
Although carbon dioxide is not the strongest
absorber of outgoing long-wave terrestrial
radiation, it is believed that it has the greatest long-
term potential for raising global temperatures.
Most attention has therefore been directed to the
increase in the concentration of carbon dioxide
from 280 ppmv (parts per million by volume) at
the beginning of the Industrial Revolution in the
eighteenth century to current levels of 360 ppmv
(Figure 2.1). The annual increase of about 1.8
Global warming is a term that entered the domain
of both popular and scientific literature during the
1980s. It is closely linked with the idea of an
increasing greenhouse effect, which was first
calculated by a Swedish chemist, Svente August
Arrhenius, in 1896 (Arrhenius 1997). It is believed
that our atmosphere acts rather like a greenhouse,
in which the glass allows solar radiation to pass
through, where it is converted into heat. This heat
is absorbed by the soil before being radiated out as
long-wave radiation and intercepted this time by
the glass, which re-radiates some of the energy
back into the greenhouse. The atmosphere has
properties rather similar to the glass of the
greenhouse, hence the 'greenhouse effect',
originally postulated by the French mathematician
Jean-Baptiste Fourier (1824).
Global warming would seem to imply that the
whole atmospheric system is warming up as a
result of the greenhouse effect, but this is far from
certain. Once the nature of the problem has been
outlined, three main areas of investigation will be
addressed. First, there is the scientific evidence for
global warming; second, the study of the likely
impacts and third, the formulation and
implementation of strategies to cope with such
impacts. The contribution of geographers has
chiefly been in the applied field of impact studies.
