Carbon dioxide has become one of the “defining molecules” of our century, due to its role in Earth's climate. This text traces the development of the perception of carbon dioxide through the ages. With layman summaries at the beginning of each chapter and extensive literature references and notes, the text takes the reader through the history of our understanding of the gas, from its early discovery as a separate gas in the mid-17th century to the recognition of its radiative properties and impact on climate in the late 19th and 20th century. The text describes the world's slow efforts to control the rise in carbon dioxide over the last 50 years and concludes by setting the stage for the Paris climate accords and subsequent negotiations. The world must reduce the emissions of carbon dioxide fast, and this book discusses options to achieve that goal. Han Dolman is a climate scientist and director of the Royal NIOZ, the Netherlands Institute for Sea Research, as well as a Professor at the Department of Earth Sciences, Free University of Amsterdam. For many years, his work has been centered around the global carbon cycle and its relation to our climate. Over the length of his career, he has been involved in several international research programs such as the Global Climate Observing System.