Cause-effect pathway

The emission of greenhouse gases will cause a rise in the earth’s atmospheric temperature which ultimately leads to increased damage to Human health and Ecosystems, this overview focuses on the ecosystems.

Modeling approach

A marginal approach for calculating the characterization factors is followed, meaning that the additional impact of a marginal increase in greenhouse gas emissions using today’s situation as the reference state. Impact is measured in potentially disappeared fraction of species for ecosystem quality.

Value choices

A number of choices have been made for the calculation of the characterization factors, namely:

• The time horizon over which effects are assessed
• Whether fish are representative of the freshwater ecosystem as a whole

Depending on which future scenario one chooses, different effects may be considered certain or uncertain. These are summarized below:

Spatial variability

Climate change is a global phenomenon; the effect of the greenhouse gas is location-independent because the emitted greenhouse gas is assumed to spread evenly throughout the entire atmosphere.

Characterisation factors

The following equation can be used to calculate the characterisation factors (CF):

where GWP is the Global Warming Potential of greenhouse gas x. TH is the time horizon δTEMP is the temperature increase due to the release of 1 kg of CO₂ and EF is the effect factor for a given Area Of Protection (AOP), in this case, either freshwater or terrestrial ecosystems.

GWPs are used to compare the effect of different greenhouse gases relative to the reference gas (CO₂), because the atmospheric lifetimes of greenhouse gases differ they are time-horizon dependent. By multiplying the GWP (in kg CO₂ equivalents) by the effect of CO₂ on the global temperature increase and the effect factor of a temperature increase on ecosystems the final characterization factor can be obtained.