There are different ways of doing that, used with greater or lesser success in different contexts, for example by creating markets for carbon or sulphur dioxide emissions (treating the right to emit as a limited good that can be traded), by levying taxes on certain types of activity that have an impact on the environment, or by offering incentives for the introduction of clean or energy-efficient technology. But there are not always straightforward answers, especially when there is a perceived tension between environmental and development imperatives. I say perceived, because in my experience working in previous jobs on the interface between environment and development, it’s often the case that it isn’t a direct choice between the two – indeed sometimes it’s a choice between an approach that provides both and an approach that provides neither.
There were some interesting questions from the students, mostly about climate change – which is the biggest externality of all – and the future of the international agreements on reduction of carbon emissions. On that issue, the next few months are a crucial time that should see agreement on the shape of a post-2020 legally binding global agreement on emissions reductions. The UK will be pushing hard for a strong and effective agreement.