this type of metric allows for overall progress in decarbonising the energy sector to be tracked over time however the larger the scale of assessment and the longer the time horizon for assessment the more difficult and uncertain it becomes to attribute an outcome or impact to a specific intervention when coupled with expost evaluation and later compared to the intended objectives of a project such information can form a useful evidence base for evaluating effectiveness unlike mitigation the ultimate impacts of specific interventions eg increased adaptive capacity and resilience are difficult to model exante or measure directly