It might seem strange to say it, but I am a global warming skeptic because of Carl Sagan.This might seem strange because Sagan was an early promoter of the theory that man-made emissions of carbon dioxide are going to fry the globe.
But it’s not so strange when you consider the larger message that made Sagan famous.
As with many people my age, Sagan’s 1980 series “Cosmos,” which aired on public television when I was eleven years old, was my introduction to science, and it changed my life. “Cosmos” shared the latest developments in the sciences of evolution, astronomy, and astrophysics, but its real heart was Sagan’s overview of the history of science and the distinctive ethos behind the scientific method. Sagan returned again and again to one central theme: that the first rule of science is to follow the evidence wherever it leads, regardless of one’s wishes or preconceptions. He spoke eloquently about the Ancient Greek Pythagoreans and their attempt to suppress the facts about “irrational numbers” that didn’t fit their theory. And he spoke admiringly about the 17th-century astronomer Johannes Kepler, who started out pursuing a theory in which the planets move in circular orbits reflecting the ratios of the perfect Pythagorean solids—and ended up being driven by the evidence to reject this theory and discover completely new laws of planetary motion.
I didn’t end up becoming a scientist, but I absorbed Sagan’s basic lesson and have tried my best to adhere to it in my own field: follow the evidence wherever it leads.
But this can be a difficult rule to follow. It is easy to spot the unexamined assumptions of others, but harder to root out your own prejudices. A few years ago, while watching “Cosmos” again for the first time in 25 years, I was reminded that Sagan did not always practice what he preached, and his error sheds light on the global warming theory’s original sin against science. It is a sin that has only gotten worse and which explains the scandalous state of today’s debate over global warming.