Being aware of the urgency and importance of climate change is not enough to tackle it effectively. To avoid the worst climate outcomes, decisive action has to be taken. But what realistic options do we have? Since our resources are limited, is it better to act now or wait until we have more advanced and less expensive technology? How big do our abatement efforts have to be? This MOOC will help you understand how economists try to answer these questions and find the optimal course of action. Most important, it will give you the conceptual tools to draw your own conclusions. In the first part of the MOOC, you will learn about the two main approaches used by economists to determine when and how much we should invest in the fight against climate change. The first method is the net-present-value approach. Here the social discount rate plays a central role in determining optimal policy, by showing how future benefits and costs can be compared and made comparable (‘present-valued’) with expenditures today. In the second approach you will learn how Integrated Assessment Models (IAMs) work. In particular, you will study in detail the strengths and weaknesses of one of the most popular IAMs, the DICE model, developed by Nobel laureate Professor Nordhaus. This model tries to figure out the optimal course of action by providing a simplified account of the science, the technology and the economics of the problem. The second part of this MOOC then explores the different types of economic policies that decision-makers can adopt. You will be introduced to different methods used to control emissions, such as carbon taxes, regulations and standard-setting. You will also learn about the most developed emissions trading markets around the world and their effects on the economy. This MOOC is for those who wish to understand the economics of climate change and use this understanding to form their own informed opinion about the policies on which we can rely to tackle it. It is not necessary to have specialized prior knowledge, apart from basic familiarity with economic concepts such as utility functions. We do suggest, however, taking the first MOOC of this specialization before starting this one in order to gain a simple but solid understanding of the physical and technological aspects of the problems.