Emission Trading Restrictions with Endogenous Technological Change

In this paper we use a simple climate model for endogenous environmental technical change in order to analyse the effects on equity and efficiency of placing different degrees of restrictions on trade in the market of pollution permits. The model is obtained by incorporating in Nordhaus and Yang (1996)'s RICE model a notion of induced technical change close to the one proposed in Goulder and Mathai (2000). With the help of such a model, we assess the pros and cons of introducing ceilings on emission trading. In particular, we analyse both the cost effectiveness and the distributional effects of placing restrictions of trading emissions. The analysis takes into account the role of environmental technical change that could be enhanced by emission trade limitations. However, this effect is shown to be offset by the increased abatement cost induced by the larger than optimal adoption of domestic policy measures when ceilings are made binding. Hence, our analysis provides little support for quantitative restrictions of emission trading, even when these restrictions actually have a positive impact of technical change. Even in terms of equity, ceilings find no justification within our theoretical and modelling framework. Indeed, we find that flexibility mechanisms in the presence of endogenous technical change increase equity and that the highest equity levels are achieved without ceilings, both in the short and in the long run.