Do Scientists Ever Change Their Minds? A Flashback to Nuclear Winter

Of course we do!

We scientists get accused of thinking that we know all the answers, but among the scientists I know, this is not the case. It is particularly evident among global-warming denialists: they think that the 99 percent of scientists who accept Global Warming science are closed minded and totally unwilling to consider the facts as presented by the oil companies and the think tanks that they sponsor.

But I have a story to tell that only my older readers will remember, a story that shows how scientists can, in fact, change their minds. It is the story of Nuclear Winter.

The concept of Nuclear Winter entered scientific and public consciousness with something of a splash. In a 1983 issue of Science, two days before Christmas, a pair of articles appeared. The first one claimed that a nuclear exchange between the United States and the USSR would put so much smoke and dust into the air that sunlight would be blocked and the surface of the Earth would freeze. In fact, it would freeze so deeply that it would never thaw. This is because ice reflects sunlight into outer space. A planet covered with ice could not warm up because it would reflect all the sunlight that it would need in order to warm up. The authors did not consider the “dirty snow effect,” in which the dust and smoke would settle on some of the ice, absorb sunlight, and melt the ice, to be important. This one paper, written by Turco, Toon, Ackerman, Pollack, and Sagan (yes, Carl Sagan)—referred to by cognoscenti as the TTAPS paper—painted a stark picture of the fate of the Earth that had not been considered previously. The second paper detailed all the extreme consequences that such a deep freeze would have upon all life on Earth. Merry Christmas, everybody!

By 1984 everyone was talking about nuclear winter. I did not think about it very much, until I had sort of a political conversion experience on Easter Day 1984 and became an anti-nuclear activist. And then I told everyone I could—in particular, my laboratory and discussion sections that I taught as a graduate teaching assistant—about it.

This was about the same time that Global Warming science started to get broadly noticed. While research into Global Warming was already a couple of decades old, it was not talked about very much before about 1984. Global Warming and Nuclear Winter were, therefore, both fledgling theories at that time. In case you wonder how they could both be true, it is simple: Global Warming if you don’t have nuclear war, Nuclear Winter if you do.

That’s when the two theories started to diverge. As more scientists investigated Nuclear Winter, they began to get skeptical. The numbers were a little off. Maybe that dirty-snow effect was a little more important than previously thought. Maybe the smoke and dust would settle fast enough that the Earth would not have a chance to cool off very much. The principle of Nuclear Winter was sound, but the new calculations began to show that the cooling after nuclear war would not be as profound as previously estimated. I remember that by 1986 some scientists were talking about Nuclear Autumn.  And not long after that, Nuclear Winter was just not discussed very much by scientists.

Meanwhile, the evidence for Global Warming became clearer and clearer. Not the least of the evidence was that, since the 1980s, nearly every year has been one of the hottest on record. The arctic ice really has been melting and getting thinner. The Northwest Passage really did open up. Glaciers really have retreated. Global Warming science has advanced as Nuclear Winter science has retreated.

Scientists were willing to give up the theory of Nuclear Winter, even those like me who held it with an almost gospel intensity. Scientists are also willing to give up the theory of Global Warming, should the evidence ever warrant it. I say this because scientists have in fact changed their views about a major global issue that has political consequences. But the evidence supporting Global Warming science is so massive, and of so many different kinds (temperatures, ice, tree buds, bird migrations, methane bubbles in Siberia), that this is extremely unlikely to happen. I guess it could. I guess we might even find out that the geocentrists were correct after all. And if it does turn out that Global Warming scientists, or Copernicus, were wrong, scientists will (eventually) admit it.

Oh, I forgot one little thing. The Great God Donald Trump has proclaimed that Global Warming theory was invented by the Chinese as a way of ruining our economy. Well, Trump has spoken. That takes care of that. Evidence? God doesn’t need evidence.

In Memory of Lynn Margulis

This essay will also be posted on my website at www.stanleyrice.com.

One of the greatest evolutionary scientists, Lynn Margulis, died last November 22. In this essay I would like to reflect on her contributions to our understanding of the world. Not just of a narrow aspect of science, but the whole world.

Lynn was a child prodigy who began her university studies at age 14. In graduate school, she studied genetics, and married her fellow graduate student, Carl Sagan (who was as creative and large a thinker as she). She was not content to just learn what others said about genetics. She wanted to understand why some traits were inherited only through the mother’s side. These traits appeared to be passed on not through the chromosomes in the nucleus but through the mitochondria, which are tiny energy factories inside of most cells. Some plant traits appeared to be passed on through chloroplasts, the tiny green photosynthesis factories in many plant cells. This meant that mitochondria and chloroplasts had, and used, their own DNA. She wondered why they had that DNA. When she read about the work of some Russian scientists in the early twentieth century, she had her answer. Mitochondria and chloroplasts started off as bacteria, which moved into and took up residence inside of larger cells that already had nuclei. They did not consume the larger cell, nor did it consume them. Instead they formed a permanent partnership, which has been going on for billions of years. Mitochondria and chloroplasts began, she said, by symbiosis—cells living together. The result was the genesis of a new, complex kind of cell. She called this process symbiogenesis.

When Lynn Sagan (later Margulis) wrote her paper, it was rejected fifteen times. She was persistent. Finally it was published. At first her ideas were scorned. But in less than a decade, most biologists were convinced that she was right. When I went to hear her speak, while I was a sophomore at the University of California, Santa Barbara (it was the first scientific seminar I ever attended), she was well received, even though the professor who introduced her made some off-color jokes. At the time, I was a creationist, and I thought that there were only two alternatives to the origin of a complex cell: either gradual evolution, or sudden creation. Lynn Margulis presented a third alternative. Her view was entirely evolutionary, of course; but the host cell and the bacteria had evolved, separately and gradually, then suddenly merged together.

Today Margulis’s view of the origin of mitochondria and chloroplasts is a textbook standard. Scientists are working on an even more amazing example of symbiogenesis: many believe that the nucleus itself is the evolutionary descendant of a bacterium that moved into a larger cell that did not yet have a nucleus. I suspect that this idea would have been too wild even for Lynn in the early days.

In her final years, Lynn was looking for evidence that cilia and “flagella” of complex cells (such as paramecia) were the evolutionary descendants of spirochete bacteria. She had some good circumstantial evidence, but never did find proof.

She was also the principal biological champion of the “Gaia” view of the Earth, a view first proposed by atmospheric scientists James Lovelock. All of the organisms of the Earth form a single network of life. The Earth is therefore not just the home of life, but is alive. Not every component of the Earth is alive, of course; but neither is every component of a cell. A cell has living components, such as mitochondria, and nonliving components, such as water. But nobody would say that a cell is not alive. By the same reasoning, the Earth is alive.

Lynn was pugnacious. She was not afraid of a good scientific debate. And she was not afraid to be wrong. Clearly she was wrong in her assertion that HIV is not an infectious virus. But if she had never taken the risk of being wrong, would she ever have had the insights that changed modern biology?

I had a chance to talk with Lynn Margulis in 2004, as I was preparing my Encyclopedia of Evolution. She was 66 years old at the time, and could have retired comfortably and with renown. But she was still fighting for recognition of yet more of her insights. I mispronounced her name, and she corrected me: the emphasis is on the first syllable, Margulis. She said I would only be allowed to make that mistake once. I didn’t make it again. She enjoyed what I had written in my encyclopedia but was not afraid to point out what she considered errors. When I dedicated Life of Earth to her last year, she left me a phone message saying that the dedication brought tears of happiness to her eyes. She bought copies and left them for students to read at the University of Massachusetts, where she worked. I am glad to have brought a little joy and appreciation into the life of this great scientist.

We can carry on Lynn’s legacy if we continue to think big about the world. When Lynn started, most scientists were trying to decompose the big picture down into component parts. But now, many scientists consider that the interactions of those components are the most important thing. An entire research institute, the Santa Fe Institute, is devoted to understanding complex interactions and emergent properties. Geneticists now know that humans and mice have about the same number of genes, and most of them are the same genes; the big difference between a mouse and a human is not the genes but the interactions among the genes. I like to think that Lynn contributed greatly to this important change in the scientific view of the world.

Announcement: I just posted a new YouTube video on www.youtube.com/StanEvolve. It will be up soon. Darwin comments on…Newt Gingrich?

Also, please send comments about what you would like to discuss, and thanks for the comments received.