 A second question is “Who should bear the costs of mitigation and adaptation?” Mitigation will often involve economic (and other) types of cost. For example, if a carbon tax is levied on goods then purchasers of those goods will be financially worse off. Sometimes mitigation policies come with benefits (for example, regulations discouraging car use are likely to improve air quality; encouraging people to cycle rather than drive may improve physical fitness). In many cases, however, the policies come with a cost. Likewise adaptation policies (such as designing cities to cope better with heatwaves) will come at a cost. Who should pay for these? Let us call this the Burden-Sharing Question.