This course begins by exploring the factors that set the Earth's temperature, considering the basic equation, Energy in = Energy out. We focus on the role of astronomical factors (sunspots and the eccentricity, obliquity, and precession of Earth in its orbit around the Sun), the reflectivity of Earth's surface, and the composition of the Earth's atmosphere in setting the Earth’s climate.
The temperature record, based on instrumental measurements, strongly indicates that the Earth has been warming over the last several decades, and dramatically so since 1975 when Wally Broecker, a former lecturer in Frontiers of Science, first coined the term "global warming." At the same time, the concentration of greenhouse gasses in the atmosphere, most prominently carbon dioxide, has been rapidly increasing. To put these recent changes in context of past data, we learn about paleoclimate proxies (e.g. tree rings and ice cores) and how it is that scientists can learn about the temperature and atmospheric content going back thousands and even millions of years ago.
With this knowledge, we confront past data, climate models, and fictions that lack scientific basis. We consider various tools used in climate science that allow scientists to compare contemporary climate change with natural changes that have occurred in the past, as well as to generate future climate forecasts. By investigating carbon isotope content of carbon dioxide in the atmosphere, we learn about the origin of the extra carbon and the role that humans have played in its release into the atmosphere. Finally, we explore the role of positive and negative feedback loops and why they make climate modeling particularly challenging. Feedback loops play an important role not only in climate, but in various biological processes, economics and more, and represent a critical scientific habit of mind taught in this course.
