The Critical Load concept, emerged in the late 1980s as a response toan expressed need from especially policy makers to create more exactand scientifically based policy tools for the abatement of transboundary air pollution in Europe (Gehring, 1994; Wettestad, 2000). The concept has mainly been used in international negotiationson emission reductions related to the second-generation protocols, tothe Convention on Long-Range Transboundary Air Pollution (CLRTAP), i.e. the 1994 Oslo protocol and the 1999 Gothenburg protocol.
To create a policy based on scientific findings of effects in nature was, by policy makers in the CLRT AP regime, seen as an improvement in relation to the uniform emission reductions, used in earlier protocols. Equal percentage cuts were viewed as arbitrary, economically ineffective and unfair. Arbitrary, as there was no solid scientific base to support the cuts. Ineffective, as the cost for reduction was different in different parts of Europe. Unfair as uniform emission reductions had failed to take into account that ecosystem sensibility varies. The introduction of Critical Load in the CLRTAP can hence be described as a change from a focus on equity of reduction, based on equal commitments for different countries to a focus on equity of environmental effects and economical commitments. The solution to these problems was the Critical Load concept which estimates ofnature's limits to different types of pollutants were aimed to serve asthe base for cost-efficiency calculations, creating the desired policy. The shift from equal percentage cuts to emission cuts based on effects led to an increased importance of scientific estimations (Biickstrand, 2001; Cresser, 2000).
Abstract is an abridged version of the introduction.