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Climate change global Stratospheric ozone depletion
Extraction of abiotic resources Extraction of biotic resources
Acidification Nutrification
Human toxicity Ecotoxicity
local
Photo-oxidant formation Land use

FIGURE 3.3 The need for spatial differentiation in different impact categories. (From UNEP
DTIE, 2003).

related to other categories, such as energy requirement or land use. Extraction of
biotic resources is mainly related to the extraction of specific types of biomass from
the natural environment. The rareness and regeneration rate of the resources is
generally used as indicator (SETAC-Europe, 1999).

3.3.2 CLIMATE CHANGE: GLOBAL WARNING POTENTIAL

Most of the radiant energy received by the Earth as short-wave radiation is reflected
directly, re-emitted from the atmosphere, or absorbed by the Earth’s surface as longer
infrared wave radiation (IR). This natural greenhouse effect is increased by manmade
emissions of substances or particles that can influence the Earth’s radiation balance,
thus raising the planet’s temperature.
Many of the substances emitted to the atmosphere as a result of human activities
contribute to this manmade greenhouse effect and must be classified in this impact
category. Listed in order of importance, they are (Hauschild and Wenzel, 1998):

• CO (carbon dioxide)
2
• CH (methane)
4
• N O (nitrous oxide or “laughing gas”)
2
• Halocarbons (hydrocarbons containing chlorine, fluorine or bromine)
The potential contribution to global warming is computed with the aid of a
procedure that expresses the characteristics of a substance relative to those of the
other gases. The Intergovernmental Panel of Climate Change (IPCC) has developed
a characterization factor system that can weight the various substances according to
their efficiencies as greenhouse gases (Houghton et al., 1995). This system can be
used in political efforts to optimize initiatives to counter manmade global warming.
The system classifies these substances according to their global warming poten-
tial (GWP), which is calculated as the anticipated contribution to warming over a
chosen time period from a given emission of the substance, divided by the contri-
bution to warming from emission of a corresponding quantity of carbon dioxide
(CO ). Multiplying a known emission of greenhouse gas by the relevant GWP yields
2
the magnitude of the CO emission that, under the chosen conditions, will result in
2
the same contribution to global warming: the emission of the greenhouse gas
expressed as CO equivalents.
2
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