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Assets in the fossil fuel industries are at risk of losing market value due to anticipated breakthroughs in renewable technology and governments stepping up climate policies in the light of the Paris commitments to limit global warming to 1.5 or 2 degrees Celsius. Stranded assets arise due to uncertainty about the future timing of these two types of events and substantial intertemporal and intersectoral investment adjustment costs. Stranding of assets mostly affects the 20 biggest oil, gas and coal companies who have been responsible for at least a third of global warming since 1965, but also carbon-intensive industries such as steel, aluminium, cement, plastics and greenhouse horticulture. A disorderly transition to the carbon-free economy will lead to stranded assets and legal claims. Institutional investors should be aware of these financial risks. A broader definition of stranded assets also includes countries reliant on fossil fuel exports and workers with technology-specific skills.

If global warming is to stay below 2°C, there are four risks of assets stranding. First, substantial fossil fuel reserves will be stranded at the end of the fossil era. Second, this will be true for exploration capital too. Third, unanticipated changes in present or expected future climate policy cause instantaneous discrete jumps in today's valuation of physical and natural capital. Fourth, if timing and intensity of climate policy are uncertain, revaluation of assets occurs as uncertainty about future climate policy is resolved. E.g. abandoning climate policy plans immediately boosts scarcity rent, market capitalization, exploration investment and discoveries. To explain and quantify these four effects, we use an analytical model of investment in exploration capital with intertemporal adjustment costs, depletion of reserves and market capitalization, and calibrate it to the global oil and gas industry. Climate policy implements a carbon budget commensurate with 2°C peak warming and we allow for different instruments: immediate or delayed carbon taxes and renewable subsidies. The social welfare ranking of these instruments is inverse to that of the oil and gas industry which prefers renewable subsidy and delaying taxes for as long as possible. We also pay attention to how the legislative "risk" of tipping into policy action affects the timing of the end of the fossil era, the profitability of existing capital, and green paradox effects.

A simple integrated assessment framework that gives rules for the optimal carbon price, transition to the carbon-free era and stranded carbon assets is presented, which highlights the ethical, economic, geophysical and political drivers of optimal climate policy. For the ethics we discuss the role of intergenerational inequality aversion and the discount rate, where we show the importance of lower discount rates for appraisal of longer run benefit and of policy makers using lower discount rates than private agents. The economics depends on the costs and rates of technical progress in production of fossil fuel, its substitute renewable energies and sequestration. The geophysics depends on the permanent and transient components of atmospheric carbon and the relatively fast temperature response, and we allow for positive feedbacks. The politics stems from international free-rider problems in absence of a global climate deal. We show how results change if different assumptions are made about each of the drivers of climate policy. Our main objective is to offer an easy back-on-the-envelope analysis, which can be used for teaching and communication with policy makers.

Keeping climate change within limits requires that most of the available carbon‐based energy sources need to be abandoned underground. We study how fast and how much this transition to carbon‐free energy needs to occur within a welfare‐maximizing Ramsey growth model of climate change. Our model also addresses the market failure in the development of clean energy which leads to an under‐provision of renewable energy, delays the transition time to the carbon‐free era and reduces the amount of dirty fuels locked upin situ. Optimal policy requires an aggressive renewables subsidy in the near term and a gradually rising carbon tax which falls in long run. We also study the transition timing and the performance of recently proposed policy rules for the carbon tax.