In shaping and implementing emission abatement policies, decision makers often have to choose between strategies that are not immediately comparable in terms of their impact on multiple emissions. For example, a move away from diesel to petrol as a vehicle fuel would lead to reduced emissions of SO2 and particulates but increased CO2 emissions, while the opposite substitution would have the converse effect. Which option is to be preferred? To answer questions like these, some form of weighting must be applied in order to apportion a relative value to cuts in each of these emissions.
This study explores two issues. With a view to improving the quality of environmental policy making, at both the design and implementation stage, should some form of explicit national protocol be introduced for emissions weighting? Secondly, should a standardised set of weighting factors be drawn up for this purpose? The focus of the study was on the everyday problems facing policy makers who need to weigh up disparate forms of emission (reduction).
The study shows that at present any mutual weighting of emissions is generally implicit. The factors guiding policies in this realm are largely contingent and many policy makers would welcome an explicit weighting procedure, particularly as this would improve the transparency of decision making. As yet, however, there is insufficient information to draw any conclusions on the desirability of a single, standardised set of weighting factors for use at the national level.