Man-made emissions of greenhouse gases are related to climate change and its consequences. This relationship can be represented as a cause-effect chain consisting of emissions of greenhouse gases, change in atmospheric concentrations, radiative forcing, climate change, climate impact, and related economic damage. The GWP has been criticized as being based on an oversimplification of the nonlinear relationship between emissions, radiative forcing, and climate impact, that cannot be represented one-dimensionally. This can lead to a misunderstanding of the concept of 'equivalence' embodied in the GWP procedure: for example, emissions that are numerically equivalent (in terms of CO2 equivalent) are not equivalent in terms of their effect on temperature changes that may occur in the long run. Further criticisms are related to the use of the so-called unit impulse response function and to the fact that constant background atmospheric conditions are considered by the IPCC in the calculation and application of GWPs. In other words, according to some authors, temporal changes in system conditions and capacity of response are not sufficiently considered. The time horizon (H) is also a debated question, since the climatic effects of emissions depend on the residence time of greenhouse gases (50-200 years for CO2; 8.4-12 years for CH4; 114-120 years for N2O; 3200 years for SF6) and what aspect of climate change is considered.
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