2016-17 CAS Lecture Series - January 13, 2017
Global Warming: What We Know and What We Don't Know
David J. Hefand, Columbia University
The Earth’s climate is changing. That’s both beyond dispute and nothing new. The important questions are What’s driving this change? How fast will change occur? What does the future hold? Few public debates are carried out with so much misinformation and irrational exuberance. So now for something completely different: a dispassionate analysis of what we actually know and what we don't yet know about climate change. My approach is to distinguish facts from fictions, and physics certainties from feedback uncertainties. Every planet's temperature is controlled by a simple balance between the energy it receives and the energy it radiates back into space, and we examine each of the factors affecting this balance in turn: astronomical phenomena, the reflectivity of the Earth, the composition of the atmosphere, and the state of the oceans. Past climates are reconstructed to test our understanding; models are developed to predict what lies ahead. The goal is to provide a basis for the construction of a rational public policy response to Earth's changing climate.
Bio: David J. Helfand, a faculty member at Columbia University for thirty-nine years, served half of that time as Chair of the Department of Astronomy. He is the author of nearly 200 scientific publications and has mentored 22 PhD students, but most of his pedagogical efforts have been aimed at teaching science to non-science majors. He instituted the first change in Columbia's Core Curriculum in 60 years by introducing science to all first-year students. In 2005, he became involved in the effort to create Canada's first independent, non-profit, secular university, Quest University Canada. He was a Visiting Tutor in the University's inaugural semester in the Fall of 2007 and served as President & Vice-Chancellor from 2008 to 2015. He also recently concluded a four-year term as President of the American Astronomical Society. He is now a member of the Executive Committee of the Board of Science Counts, an organization formed to communicate to the public the importance and impact of publicly funded fundamental research. His recently released book, “A Survival Guide to the Misinformation Age” provides the essential tools informed citizens must acquire to combat the tsunami of mis- and dis-information that threatens rational approaches to personal decision-making and the formation of good public policy.