Geologists by nature and training take a long-term view. The professor clicks a slide onto the classroom screen. It reads: “In 1958, Robert Giegengack first heard about Global Warming!”
There are a few chuckles in the classroom. Giegengack waits a beat for comic effect. “I said, ‘Big deal,’” he tells the class. “I lived in New England.”
He’d been born in Brooklyn, but spent much of his life in New Haven. After a false start studying civil engineering at Yale, Giegengack discovered geology and got hooked. He got a master’s degree in Colorado, then returned to Yale for a doctorate and focused his research on rocks and climate change. He arrived as a young assistant professor at Penn just about the time the first Earth Day in 1970 was reflecting — and driving — an interest in the environment. Giegengack got the assignment to set up the university’s environmental studies program, which he would run for more than three decades.
A few years ago, Giegengack told the Pennsylvania Gazette, the school’s alumni magazine, that the environmental analysis course he’s teaching today often attracts students who want to be environmental activists and carry picket signs outside the offices of the bad guys in the military-industrial complex. “But I want them to understand that these questions are enormously complex,” he went on.
Yes, they are. I ask Gieg for a private tutorial based on the lectures he gives his students to make them consider the scientific complications of climate change. We sit one afternoon at a conference table near his office, his laptop open and the PowerPoint ready to go. Charts appear, one after another.
Giegengack may have a personal 50-year perspective on global warming, but the time range he prefers to consult is more on the geologists’ scale. The Earth has been warming, he says, for about 20,000 years. We’ve only been collecting data on that trend for about 200 years. “For most of Earth history,” he says, “the globe has been warmer than it has been for the last 200 years. It has only rarely been cooler.” Those cooler periods have meant things like two miles of ice piled over much of what is now North America. Nothing to be nostalgic for.
The professor hits a button on his computer, and the really long-term view appears — the past 650,000 years. In that time, the Earth’s temperature has gone through regular cycles of rise and fall. The best explanation of those cycles was conceived by a Serbian amateur scientist named Milutin Milankovi´c. Very basically, Milankovi´c said this: The Earth’s orbit around the sun is more or less circular, but when other planets align in certain ways and their gravitational forces tug at the Earth, the orbit stretches into a more elliptical shape. Combined with the tilt of the Earth on its axis as it spins, that greater or lesser distance from the sun, plus the consequent difference in solar radiation that reaches our planet, is responsible for long-term climate change.