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We develop a one-dimensional energy balance climate model with heat transportation across locations. We introduce the concept of potential world GDP at time t, and we introduce, through the temperature function, spatial characteristics into the damage function which make damages latitude dependent. We solve the social planner’s problem and characterize the competitive equilibrium. We define optimal taxes on fossil fuels and profit taxes on firms that extract fossil fuels. Our results suggest that if the implementation of international transfers across latitudes is not possible, then optimal taxes are spatially non homogeneous and tend to be lower at the poor latitudes. The degree of spatial differentiation of optimal taxes depend on heat transportation. We also locate sufficient conditions for optimal mitigation policies to have rapid ramp-up initially and then decrease over time. By employing the properties of the spatial model and approximating solutions, we show how to study the impact of thermal transport across latitudes on welfare inequality.

We couple a one-dimensional energy balance climate model with heat transportation across latitudes, with an economic growth model. We derive temperature and damage distributions across locations and optimal taxes on fossil fuels which, in contrast to zero-dimensional Integrated Assessment Models, account for cross latitude externalities. We analyse the impact of welfare weights on the spatial structure of optimal carbon taxes and identify conditions under which these taxes are spatially nonhomogeneous and are lower in latitudes with relatively lower per capita income populations. We show the way that heat transportation affects local economic variables and taxes, and locate sufficient conditions for optimal mitigation policies to have rapid ramp-up initially and then decrease over time.

A simplified energy balance climate model is considered with the global mean temperature as the state variable, and an endogenous ice line. The movements of the ice line towards the Poles are associated with damage reservoirs where initial damages are high and then eventually vanish as the ice caps vanish and the damage reservoir is exhausted. We couple this climate model with a simple economic growth model and we show that the endogenous ice line induces a nonlinearity. This nonlinearity when combined with two sources of damages - the conventional damages due to temperature increase and the reservoir damages - generates multiple steady states and Skiba points. It is shown that the policy ramp implied by this model calls for high mitigation now. Simulation results suggest that the policy ramp could be U-shaped instead of the monotonically increasing with low starting mitigation gradualist policy ramp.