Global Warming: The Astronomical Factors (NEW RELEASE!)
David Helfand has been a Professor of Astronomy at Columbia University for 47 years, where he served as chair of the Department for two decades. He is also the former President of the American Astronomical Society and of Quest University Canada, and currently serves as Chair of the American Institute of Physics. Professor Helfand has received the Columbia Presidential Teaching Award and the Great Teacher Award from the Society of Columbia Graduates. He is the author of A Survival Guide to the Misinformation Age and, recently The Universal Timekeepers: Reconstructing History Atom by Atom.
Overview
The energy balance of the Earth, and thus, its temperature, is determined by a number of factors–beginning with its location in our Solar System. The light input from the Sun is, by a huge factor, the dominant source of energy that warms the Earth. But this energy input is not constant: the Sun’s output varies, the distance from Earth to Sun is in constant flux, and both the tilt of the Earth’s rotation axis and its orientation in space vary with time.
The rapid increase in global temperatures over the past 50 years is explained in quantitative detail by human alteration of the composition of the atmosphere and our changing land use. Nonetheless, some people like to shift the blame to astronomical factors.
In this program, Columbia Astronomy Professor David Helfand systematically evaluates how changes in the Sun and in Earth’s orbit impact the climate on both long and short timescales. Over times from 20,000 to 100,000 years the orbital changes are dominant, but over the last half-century of rapidly increasing temperatures, the astronomical factors account for less than 1%. Yes, humans cause global warming.