ABSTRACT
Climate-change policies aim to prevent ultimate adverse climate-change impacts, stated explicitly by the UNFCCC as 'preventing dangerous anthropogenic interference with the climate system'. This has led to the adoption of specific climate-change targets to avoid exceeding certain temperature thresholds, such as the '2° target' agreed to in Copenhagen in 2009. The UNFCCC also stated that this aim should be achieved through measures that are 'comprehensive and cost-effective'. To achieve comprehensive and cost-effective climate-change mitigation requires an assessment of the relative marginal contribution of different greenhouse gases (GHGs) to ultimate climate-change impacts.
