Professor Alan Barrett:

With regard to the modelling exercise, this is a phenomenally complicated area but we need to have some sort of a framework to think about how these things might impact. Many of the ESRI modelling exercises are data driven. We are taking the data and trying to construct somewhat artificial statistical models of the economy. The real usefulness is that it at least provides some sort of quantification. When we talk about the carbon tax going from one level to another, we need to have some sense of whether that is having an effect. That is where much of the intellectual energy goes. That is why entities such as the Department fund us to try to develop these sorts of tools so that we are at least talking a common language and working to a particular benchmark.

On the Senator's point about driving to Galway, I come back to the issue of appraisal. It would be pure opinion to say that I prefer roads or rail but the point is that it is all about how we evaluate these various investments. When the road between Dublin and Galway was being built, I am not convinced that the damage the Senator is doing to the planet as he drives - I am sure he owns a very modest car - was factored in, whereas his timesaving certainly was.