How uncertainty of air emission inventories impacts policy decisions at sub-national level. A Shift-Share Analysis undertaken in Piedmont (Italy).

Emission inventories are compiled at national and regional levels and used without taking uncertainty into account. We attempt to check whether and to what extent uncertainty related to emission inventories affect quantitative analysis used by policy makers to set strategies and implement actions at regional and sub-regional levels. We consider the regional air emission inventory of the Piedmont region in Italy. Uncertainty is calculated by adapting the insurance-based method. A hybrid accounting matrix is built and a Shift-Share analysis is undertaken for manufacturing and construction activities, and for the transport sector at regional and provincial levels. The procedure is repeated for data without uncertainty and data with uncertainty. Although in absolute terms total emissions are remarkably different, the outcomes of the Shift-Share Analysis vary among provinces: sometimes the messages are misleading when uncertainties are not included in the calculation; sometimes the differences are negligible. Some general conclusion can be drawn.