their results are summarised in table all but one of the models analysed out of assumed atmospheric concentrations of ghgs between and ppm in which is of course considerably higher than the ppm or lower implied in the paris agreement this may be taken as an indicator of the extent to which the policy debate has abandoned any link with modelling efforts attempting to estimate realistic mediumrange scenarios it should also be noted that the models considered calculate abatement costs for the energy sector rather than for the electricity sector in principle this would correspond to the level of the carbon tax required ppm parts per million