Environmental Engineering Reference
In-Depth Information
replacement of high sulphur fuels with low sulphur
alternatives.
fuelwood
Wood products harvested for use as fuel.
The removal of scrub woodland for fuelwood is a
major cause of
desertification
in the arid or semiarid
parts of Africa and Asia.
reports of exploratory expeditions which visited
the plains during one of the periods of
drought
common to the area, and observed the results of
natural
desertification
.
Great Plains
An area of temperate grassland with a
semi-arid climate in the interior of North America,
stretching for some 2,500 km from western Texas
in the south along the flanks of the Rocky
Mountains to the Canadian prairie provinces in
the north. (See also
Great American Desert,
Dustbowl
and
Pueblo drought
.)
Green Parties
Political organizations which aim to
protect the environment through the use of
established parliamentary procedures.
greenhouse effect
The name given to the ability of the
atmosphere
to be selective in its response to
different types of radiation. Incoming short-wave
solar radiation
is transmitted unaltered to heat the
earth's surface. The returning long-wave
terrestrial
radiation
is unable to penetrate the
atmosphere,
however. It is absorbed by the so-called
greenhouse
gases
causing the temperature of the
atmosphere
to rise. Some of the energy absorbed is returned to
the earth's surface, and the net effect is to maintain
the average temperature of the earth/ atmosphere
system some 30°C higher than it would be without
the greenhouse effect. The process has been likened
to the way in which a greenhouse works—allowing
sunlight in, but trapping the resulting heat inside—
hence the name.
greenhouse gases
The group of about twenty gases
responsible for the
greenhouse effect
through their
ability to absorb long-wave
terrestrial radiation
.
They are all minor gases and together make up less
than 1 per cent of the total volume of the
atmosphere.
Carbon dioxide
is the most abundant,
but
methane, nitrous oxide,
the
chlorofluorocarbons
and tropospheric
ozone
also
make significant contributions to the
greenhouse
effect
. Water vapour also exhibits greenhouse
properties, but has received less attention than the
others. Since the beginning of the twentieth century,
rising levels of these gases in the atmosphere,
associated with increasing
fossil fuel
use, industrial
development,
deforestation
and agricultural
activity, have brought about an enhancement of
the
greenhouse effect,
and have contributed to
gradual
global warming
.
grid-point models
Climate models which provide full
spatial analysis of the atmosphere by means of a
three-dimensional grid covering the earth's surface
and reaching as high as 30 km into the atmosphere.
The progressive solution of thousands of equations
G
Gaia hypothesis
Developed by James Lovelock, the
hypothesis views the earth as a superorganism in
which the living matter is capable of manipulating
the earth's environment to meet its own needs.
gas phase reaction
The conversion of
sulphur dioxide
and
oxides of nitrogen
into sulphuric and nitric
acid, all of the reactions taking place with the
various compounds remaining in a gaseous state.
general circulation models (GCMs)
Three-dimensional
models which incorporate major atmospheric
processes plus local climate features predicted
through the process of
parameterization
. They
include some representation of
feedback
mechanisms and are able to cope with the evolving
dynamics of the atmosphere as change takes place.
In an attempt to emulate the integrated nature of
the earth/atmosphere system atmospheric GCMs
are often coupled with other environmental models,
particularly those representing the oceans.
Glaciological Volcanic Index (GVI)
An index based
on acidity levels in glacial ice as revealed by ice
cores. This gives an indication of
sulphur dioxide
levels associated with past volcanic eruptions, an
element absent from both the
Dust Veil Index
and
the
Volcanic Explosivity Index
.
Global Forum
A conference of non-government
organizations (NGOs) held at the same time as the
United Nations Conference on Environment and
Development (UNCED)
. It included a wide range
of topics—from the presentation of biological
diversity to
sustainable development
—which
generally paralleled those included in the main
UNCED event.
global warming
The rise in global mean temperatures
of about 0.5°C since the beginning of the century.
The basic cause of the warming is seen by many
researchers as the enhancement of the
greenhouse
effect
over the same period, brought on by rising
levels of anthropogenically-produced
greenhouse
gases
.
Great American Desert
Common perception of the
western interior plains of North America in the
nineteenth century. The image grew out of the
