This paper forms part of an OECD project which addresses the issue of the costs of reducing CO2 emissions by comparing the results from six global models of a set of standardised reduction scenarios. The IEA model is an econometric energy model with a projection horizon to 2005. One of the major conclusions to emerge from the results presented in this paper is that even seemingly moderate CO2 emissions reduction targets would require very high carbon taxes. The reasons for this are, firstly, that the carbon taxes need to be very high to have any material impact on final prices, especially those of transportation fuels and electricity, and, secondly, that most of the decline in emissions would have to come from a reduction in energy demand because the scope for substitution is very limited over a period of 10-15 years. The model also suggests that the required carbon taxes for any target are likely to be much lower in North America than in the Other OECD region, because North ...