"Nothing is permanent," said the great philosopher Heraclitus, "except change." Tonight's episode of Cosmos was about the changes the Earth has undergone over the eons and the contribution life has made to those changes.
The story starts about three hundred million years ago, on December 23rd of the Cosmic Year, when trees first appeared on the Earth thanks to a miracle molecule known as lignin. Lignin was strong and flexible and gave trees the ability to grow taller than any life forms before or since. Lignin was also indigestible to the agents of decay, the bacteria and fungus that fed off dead plants and animals.
And so trees flourished for millions of years, pulling carbon dioxide out of the air and releasing oxygen. Trees released so much oxygen that they radically changed the climate of the Earth, allowing insects to grow to massive size. Without a mechanism for decay, the carbon in the trees became sequestered in the ground and converted into coal which built up until it was was eventually burned in volcanoes and released into the atmosphere as carbon dioxide. This release created a runaway greenhouse event known as the Permian-Triassic extinction which wiped out most of the life on Earth.
Tyson then turns his attention to the Earth's tectonic forces and the discovery of continental drift by Alfred Wegener, who died on an expedition still the subject of ridicule by his contemporaries who preferred temporary land bridge theories to explain the appearance of identical fossils on continents separated by oceans. Scientists, Tyson tells us, are human beings, with the same biases and flawed judgment all humans share.
Science is a mechanism for ferreting out those biases, but it is far from perfect. Sometimes conclusions that seem obvious in retrospect face years of denial by even the most well meaning of scientists too inured to their assumptions to see the evidence clearly. And so with the evidence of the Permian extinction sitting right before our eyes, Tyson ends with a plea for the ingenuity and courage to free ourselves from our carbon addiction.
In the global warming debate, the false choice is commonly presented that since the climate changed naturally in the past we can safely conclude that human beings are not contributing to climate change now. Lightning causes forest fires, therefore humans do not. In this episode of Cosmos, we see that we cannot so easily separate life from the Earth's other natural processes. If we are not contributing to global warming, it will be the first time biological activity on the scale of human civilization has not affected the climate.
Another argument that is commonly made is that the Earth is undergoing natural warming, an interglacial period between ice ages, and that this can account for the warming we've seen in the climate. This is, of course, also a false choice. At the same time that the Earth is warming naturally due to variations in our orbit, we are also digging up and burning more of the ancient sequestered carbon than at any time since the Permian-Triassic event. That the Earth is warming on its own doesn't make our contribution to global warming less dangerous. It makes it more dangerous, like putting on a sweater while running a fever.
If the history of Earth's violent climatic upheavals tells us anything, it's that the planet does not care whether we live or die. Extinction upon extinction upon extinction has shown us that if we want to preserve this place as our home, the onus is on us to understand how and why the climate works the way it does. No one is going to pull our bacon out of the fire except us.
Or, in the words of another great philosopher, George Carlin, "the planet is fine...the people are fucked."
The good news? Cosmos had its best ratings in a couple months last night, including a big jump among the key demographic. And this show is having an impact that goes beyond viewers, as Carolyn Porco explains: