The Climate in Emergency

A weekly blog on science, news, and ideas related to climate change


The Story of Global Cooling

I’ve been hearing climate deniers talking about a global cooling scare in the nineteen seventies for a while now, and I finally got curious about where this narrative had come from–I didn’t think it had been made up whole cloth, but I hadn’t heard word one about it from any credible source, either. You’d think that if climate scientists had thought an ice age was imminent as recently as the seventies, at least some of the scientists I know would mention it occasionally?

So, I looked into it. And I found not one but two explanations.

In one story, Peter Gwynne, a science writer for Newsweek, wrote a short article on an idea some scientists were kicking around at the time–that a thirty-year cooling trend might continue and develop into a real ice age. The article was published on April 28, 1975, and attracted enough attention that other publications picked up the story with their own articles. Books and TV shows followed.

Scientific American, my source for this particular story, explains that the cooling trend is

now believed to be a consequence of soot and aerosols that offered a partial shield to the earth as well as the gradual retreat of an abnormally warm interlude.

And that

there also was a small but growing counter-theory that carbon dioxide and other pollutants accompanying the Industrial Age were creating a warming belt in the atmosphere, and by about 1980 it was clear that the earth’s average temperature was headed upward.

Scientific American acknowledges that the global cooling thing has no legitimate place in the climate discussion today, and reports that Mr. Gwynne himself is somewhat embarrassed by the anti-scientific uses to which his writing is being put. He does stand by what he wrote, given the limits of available knowledge at the time.

Ok, but there are a couple of problems with that story, starting with the fact that the greenhouse effect was not a “small but growing counter-theory” in the 1970’s–the effect of carbon dioxide on the climate has been known since 1859. The first calculations of the human role in climate change were made in 1896.

And it’s not like global warming was some far-out thing nobody was paying attention to back in the 1970’s, either. No less a person than the fiction writer, Ursula K. LeGuin had started making oblique references to climate change as early as 1969 (her novel, The Left Hand of Darkness, includes a flawless description of the natural greenhouse effect, as well as a reference to an alien planet that is hot because “an exploitive civilization wrecked its natural balances, burned up the forests for kindling, as it were.” Several of her later books also refer to the Earth itself getting warmer, too). Perhaps more starkly, the 1970’s were when Exxon was busy figuring out what it was going to do about global warming, of which its internal documents prove it was well aware.

Beyond all that, thereĀ wasn’tĀ a 30-year cooling trend, except perhaps in a mathematical sense. According to the National Oceanic and Atmospheric Administration (NOAA), the period from the mid-1940’s to the mid-1970’s was cooler than previous years had been, but there was a lot of minor temperature fluctuation, not a consistent cooling. A cool period of relative stability is not the same thing as an oncoming ice age.

So, I did some more poking and found the second story.

Apparently, in the 1970’s, the greenhouse effect was well-known, but the cooling effect of sulfate emissions (“aerosols”) had just been discovered and it wasn’t clear yet which would prove dominant. A few climate scientists thought the aerosols might win out–between 1965 and 1979, 10% of the scientific papers on the subject predicted cooling, but 28% could make no prediction and 62% predicted warming. In other words, the coming ice age was a legitimate scientific idea for a while, but only a small minority of studies ever supported it.

I’m not actually sure, based on what I’ve read, whether anybody ever proved that sulfate emissions couldn’t have counteracted carbon emissions under some scenarios that were plausible back then. As history has actually played out, sulfate emissions have been dramatically reduced (they also cause acid rain), while carbon emissions have continued to climb. Aerosols still complicate climate predictions, but no one thinks they’re going to cause an ice age anymore.

There’s no cooling trend mentioned in there.

The way I see these two stories blending, I suspect that what really happened was that the end of the warming trend of the first third of the 20th century was taken (maybe correctly) as evidence of the cooling power of aerosols. Some climate scientists thought the aerosols could go on to trigger a cooling trend, but most did not. Peter Gwynne, being a writer who cared about science and about getting his writing published, chose to focus on the minority opinion, since that seemed more sensational at the time. He has admitted that the story “pushed the envelope a little bit,” in deference to Newsweek’s penchant for what Scientific American called an “over-ventilated style.”

The ventilation would have seemed harmless at the time, if the article was fundamentally accurate, as I’m willing to buy that it was. Nobody can represent the entire breadth of the scientific conversation on any one topic in just nine paragraphs. You have to choose which of all possible stories you’re going to tell, in order to tell any story at all.

That deniers have since pounced on his article for political and anti-scientific purposes is not Mr. Gwynne’s doing. Being co-opted is a risk all published writers run–it’s the Scylla to the charybdis of being utterly ignored.

Curiously, the one detail I thought would enter the discussion apparently didn’t, except as a note of context written long after the fact by one or another of my sources–astronomically speaking, we’re supposed to be in an ice age already.

The primary factor that dictated the glacial/interglacial cycle through recent geological history was the Milankovitch Cycle, an interaction between three separate variations in Earth’s orbit that together dramatically how much solar radiation we get at different times of the year. We’re at a point in the cycle where we should be heading into a new ice age, but aren’t because our carbon dioxide levels are too high.

The connection between that cycle and climate was confirmed in 1976, so it may be another thread of the “global cooling” story that none of my sources happened to tease out–but if not, there may have been good reason to ignore it.

The onset of ice ages is very slow. I have to cite one of my grad school classes here (Tom Wessels was the teacher–I’ve cited him as a source here before) as I haven’t been able to lay my hands on an appropriate link, but ice ages melt quickly (as in many hundreds of years) and grow slowly (as in many thousands of years). In fact, the warmest point of our current interglacial (before now, anyway) was thousands of years ago. No, the cooling was never enough to initiate continental glaciation on North America or Asia, but cooling was in progress.There is an excellent illustration of this cooling, and how long and consistent it was, here (yes, that is a web comic, but this one’s not a joke).

Sliding towards an ice age doesn’t look like anything special, it turns out. More or less, it looks like all of human history.



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The Fault Lies Not in Our Stars

I recently happened upon an article about a prediction that today would see massive earthquakes caused by a planetary alignment. Apparently, Nostradamus predicted something of the sort as well. The author (quite correctly) explained that the movement of other planets does not and cannot cause earthquakes–he quoted a “contrary view” (contrary to the earthquake prediction) that the gravitational influence of the moon is much greater than that of the other planets, and that because its orbit is elliptical, the moon’s gravitational influence on us varies every month. Since we do not get massive earthquakes as the moon moves around, there is no way the other planets could cause earthquakes.

Well and good.

But the author went on to state that in his “opinion,” the sun has a stronger effect on earthquakes than other planets or the moon. And that is a very odd word to use in this context–“opinion.”

I do not mean to make fun of this man, or the several people who commented on the article. They are all obviously thinking carefully about important issues, and they all apparently care about the truth, reject fear-mongering, and support critical thinking about what they read and hear. What they’re not doing, though, is thinking scientifically. Lots of people don’t think scientifically–I’m willing to bet that even most scientists don’t think scientifically all of the time. There are, in fact, some things science is no good for. But I’ve encountered a lot of misunderstandings about what science actually is and these misunderstandings make public discussion of issues like global warming much harder.

Science is a process.

It is not a world view. There is no reason, for example, that telepathy is not scientific. It’s true that science has found no evidence confirming the existence of telepathy, and it seems unlikely at this point that it ever will–but it has found evidence that some animals can sense electrical signals from the muscles of other animals, which sounds at least as fantastic, if you think about it. The history of science is full of things that intelligent, reasonable people considered impossible turning out to be true. World views, lists of things understood to be true or not true, possible or impossible, are the result of science, or of the other processes humans have developed for understanding our world. It’s not what a person thinks that makes him or her a scientist, but how.

The how of science is that you start with verifiable facts, look for patterns in those facts, and then go look for more facts that either confirm or refute the patterns. You keep track of the facts you verified and the patterns you noticed and how they were either confirmed or refuted.

My favorite example involves baseball.

Randall Monroe, famous among nerds everywhere for the webcomic, xkcd, also has both a blog and a book called What If? in which he uses physics to answer frankly ridiculous questions. One such question was “what happens if you try to hit a baseball that is going 90% of the speed of light?” After deciding to ignore just why and how the hypothetical baseball accelerated, Mr. Monroe explains that because air cannot move out of the way of an object going that fast, the atoms of the air and of the ball would actually undergo nuclear fusion, causing a massive explosion. Also, the batter would be considered “hit by pitch” and could advance to first base, except for being dead.

Mr. Monroe acknowledges that he’s not sure this is exactly what would happen, and obviously the experiment cannot be performed. But the point is that he did not just think up a scenario that seemed plausible to him–he used what we know of physics to make an educated guess. He could, if he wanted to, defend his guess by citing his sources and constructing an extended “if-then” argument stretching all the way back to actual observations of the behavior of air molecules and subatomic particles. Other physicists could then either confirm or refute the plausibility of his guess by constructing arguments of their own. So we might not know for sure what would happen to a baseball pitched at 90% of the speed of light, we can use reason and experience to talk about what might happen with some confidence.

It’s worth noting that an experiment on a similar scale of outlandishness has been tried–when the first nuclear bomb was detonated, obviously no one has any experience with that type of explosion. Yet the physicists responsible for the bomb predicted fairly accurately what would happen–that the thing would explode, that it would explode upon deliberate detonation and not before or after, and that the observation bunker and the people inside it would not be destroyed in the process. That is an amazing degree of predictive power.

The simplicity of the scientific process means that arguments about science work differently than arguments about anything else (at least in principle–scientists are human beings, and as such are just as capable of unexamined bias and threatened egos as anybody else). You simply find out what other people have observed and what theories about those observed phenomena have been supported, and construct a reasoned argument, the same way you might build a tower of blocks. Your opponent in debate then either offers competing observations and theories or demonstrates that you made a mistake somewhere.

There is no reason why a scientist should ever qualify a professional statement with “in my opinion,” or “I feel that….” As a teacher of mine once said, we don’t care how you feel.

We don’t care what your opinion is, does the sun actually cause earthquakes? Has anybody checked? How do you go about finding out if the sun does cause earthquakes? (What you do is keep track of changes in solar behavior and see if any of the things the sun does or any changes in the relationship between the sun and the earth correlates consistently with changes in earthquake behavior–and yes, it has been done, and no, No, the sun does not cause earthquakes).

More importantly, is the earth warming up? Do certain gasses trap heat in the atmosphere? Are human beings increasing concentrations of those gasses to the point that it is changing the climate? Has anybody checked? How do you find out?

Yes, of course, lots of people have checked, and yes anthropogenic climate change is quite real.

And yet the public discourse on the matter proceeds, like that little online discussion I found about earthquakes and astrology, by statements of opinion and belief, and by confident appeals to various emotionally potent tropes (conspiracy, for example–somehow, the idea that some powerful organization is suppressing information makes an assertion seem more believable). And none of that is necessary. A climate scientist does not have to be likeable, popular, possessed of the same political and cultural affiliations as you, or able to argue well in the public sphere in order to be right. All he or she has to do is construct a sound connection between observation and prediction. And you can always check on the validity of that connection yourself, if you want to (you may have to get a science degree or its equivalent, but you are free to do so. The information is not secret).

It’s worth noting that the scientific process is the best means of figuring out how things work that human beings have ever come up with. There are issues it is no good for (like “what is the meaning of life” and “how do I be a good friend right now?”) but if you can read these words, then you have proof that science works.

So, let’s not allow anyone to drag the discussion into the realm of opinion, ok?