This seminar examines debates over the costs - economic, environmental, and social - of climate change. We will explore how economists attempt to solve seemingly impossible problems of valuation like: how much should we value the wellbeing of current versus future generations? How much value does the ecosystem as a whole provide? We will then survey how these numbers (sometimes) enter into environmental regulatory debates. Finally, we will study how movements fighting for environmental justice adopt - or reject - the language of economics to make claims about the morality and economics of fossil fuel producers.