Image courtesy of NASA and the National Climate Assessment. Click for full story by Peter Gwynne, "My 1975 'Cooling World' Story Doesn't Make Today's Climate Scientists Wrong."
Writing about science on the internet can be challenging enough. Today's intertoobz are full of miscreants and liars and just plain whacked-out conspiracy-minded flakes. Now add in manufactured controversy over some topics in science, say biology or climate change for example, that draws considerable funding from flaky billionaires, and it can sometimes seem hopeless.
For example, a couple of weeks ago we profiled the second edition of climate scientist Michael Mann and Lee Kump's book Dire Predictions. No sooner had that review been posted than the usual suspects started posting fake reviews on Amazon and elsewhere intended to insult the authors and wave off potential readers. Given that Mike has bent over backward for the planet and this community, it would be awful nice if some of you who have bought the book would head over and post genuine reviews.
You can't spend long in forums full of ditto-heads without coming across a medley of zombie lies on climate change. One of the more underhanded claims you'll see put forth by people who absolutely know better is that climate scientists were predicting another ice age back in the '60s and '70s, but now they're claiming we're in a warming trend, so they obviously have no idea what they're talking about! They can purportedly even back it up with peer-reviewed material from the time.
This "argument" for lack of a better word is utter nonsense, but it's also quite clever in its construction. It depends on youthful memories and conflating two distinct items in climate research that went on back then. One concerned the analysis of Pleistocene ice ages; the other was the effect of sulfate aerosols vs greenhouses gases emitted by human activity.
What actually happened in the '60s and '70s with respect to ice ages and aerosols is a lot cooler—you see what I did there?—than anything you'll see on a denier site. Follow me below and learn the secret behind the trick.
When we talk abut ice ages here, we mean the geologically recent ones. We're looking exclusively at those characterized by the Laurentide ice sheet in the last part of what geologists call the Wisconsin Stage, which lasted from about 25,000 to 14,000 years ago.
In the '60s scientists began to get a clear understanding of how and why recent ice ages happened. A number of the primary forces are now referred to collectively as Milankovitch Cycles. Almost everyone knows the Earth's orbit around the sun isn't a perfect circle, it's an ellipse, but what few people know even today is that the ellipse changes over thousands of years. The Earth's orbital eccentricity cycles between slightly more elliptical with a max of about 0.07, to slightly less elliptical at about 0.00005 or very close to circular, over a period of roughly 400,000 years. The Earth also precesses on its axis every 26,000 years, the orbital plane bobbles a bit, the axial tilt varies slightly between 22 and 24.5°, and if that's not enough complexity, our home planet also traces out a lopsided, rose petal shape over eons as it orbits the sun. Combine all these things and every few 10,000 to 200,000 years or more you end up with the northern hemisphere pointed at the sun—that is, summer in the north—happening when the Earth is as far away as it can get, with a low axial tilt, during an above average elliptical phase. These are perfect conditions for an ice age.
Indeed, we now know that the more widespread Northern Hemisphere ice ages are correlated to much cooler summers and average to warm winters. Because, 1) in warmer winters there is more moisture in the air on average and thus more ice and snow falling, and 2) in a much cooler summer less of that ice and snow melts. Given hundreds to thousands of back-to-back cool summers, it piles up and begins to ooze out everywhere like a big puddle of ice cream. There's already ice to the north in the Arctic, so the growing glaciers link up and flow more freely to the south. Ice reflects a lot more sunlight than darker sea or land, causing cooler local conditions, which cause less summer melt, and the process can feedback, until thick ice is pushing into Indiana like it did 20,000 years ago. But don't go buying a new winter wardrobe anytime soon: the next time conditions are likely to be decent for the onset of a new ice age in North America is currently estimated to be somewhere in the neighborhood of 50,000 years.
Milutin Milankovich as a young and gifted student
A number of naturalists at the turn of the 20th century nibbled around the edges of these phenomena. But it was a young Serbian genius named
Milutin Milankovitch who began to tie them all together with impressive mathematical rigor, starting when he was held as a POW during World War 1. Sadly, his ideas churned around in obscure academic backwater for decades, but undeterred, he spent much of that period further refining and summarizing them. Milankovitch passed away in 1958, but he lived just long enough to get a faint, hopeful glimmer that his life's work might one day get the recognition it so richly deserved.
Because finally, beginning in the 1950s, his comprehensive, elegant analysis of the complex interplay of orbital and planetary dynamics was dusted off and re-examined, their collective effect on past climate became better understood. Over the next decade that work was modeled in the bowels of early computers and cross checked against a rapidly growing body of ancient ice cores and astronomical observations, and a new generation of scientists slowly came to appreciate that Milutin Milankovitch, working with just a few reference books on pen and paper under watch in a glorified prison cell, had quietly cracked the mystery of ice ages decades earlier! Today, he is rightly respected and highly honored as the visionary father of modern paleoclimatology.
The idea eventually filtered out of professional scientific journals and into the mainstream media of the day, which dutifully and correctly reported that more ice ages were in our distant future. Some of those media sources went farther, no doubt in search of higher circulation, and published more sensationalist -- some might even say misleading -- headlines and articles. A couple that got wide attention from the laypublic and local mainstream press were a Time magazine article in 1974 and a Newsweek piece the following year.
Here's the important thing: The study of Milankovitch Cycles that produced the scientific papers at the time and thus drove those popular magazine articles did not take man-made greenhouse gases into account. Scientists were simply trying to solve the longstanding mystery of how and why recent ice ages had occurred. They specifically ignored any modern anthropogenic effects, including fossil-fuel emissions, in predicting when conditions might be ideal for the onset of the next ice age. Some of them even stated that at the top of their papers, such as this one published in the journal Science in December of 1976:
Having presented evidence that major changes in past climate were associated with variations in the geometry of the earth's orbit, we should be able to predict the trend of future climate. Such forecasts must be qualified in two ways. First, they apply only to the natural component of future climatic trends—and not to anthropogenic effects such as those due to the burning of fossil fuels.
But if that's the case, where do the fossil fuel think-tanks get the text of scientists predicting imminent global cooling, cooling that will threaten crop production and bring on terrible winters in the next few decades? Ahh yes, indeed, this is the most underhanded part of the trick. Another field of research in the '60s and '70s was on the shorter-term effect of sulfate aerosols versus greenhouse gases. These specific particulate aerosols reflect sunlight and thus have a cooling effect; GHGs absorb heat and thus have a warming effect. And they had a minor mystery of their own to explain. Note the lull in global warming starting in the '40s and stretching into the mid '70s.
GISS Surface Temperature Analysis or GISTEMP, courtesy of the NASA Goddard Institute for Space Studies.
Nevertheless, even with that warming pause and the role sulfate particulates played coming into focus, the solid consensus at that time was the GHGs would soon
overtake the aerosols:
The paper surveys climate studies from 1965 to 1979 (and in a refreshing change to other similar surveys, lists all the papers). They find very few papers (7 in total) predict global cooling. This isn't surprising. What surprises is that even in the 1970s, on the back of 3 decades of cooling, more papers (42 in total) predict global warming due to CO2 than cooling.
A significant majority of climate scientists in the '70s were
not predicting global cooling from aerosols, quite the opposite, and they sure as hell weren't predicting another ice age in the next decade or century!
But if you're a paid liar, now you have the pieces needed to pull a bait and switch: you show people a Newsweek article predicting an ice age at some undefined time in the future. And if anyone who is halfway informed starts asking pesky questions, you link or quote text from scientific papers on aerosols from the minority view at the time asserting an era of global cooling is immediately at hand—as if they were both talking about the same thing, a new ice age is upon us the day after tomorrow! Then you go on to say that scientists—implying a consensus—were predicting an immediate ice age in the '70s and therefore we should disregard their prediction of global warming now.
Some deniers have even been know to toss in a magazine cover or three, often photoshopped, featuring stories about the 1970s energy crisis or other then current events, that had ice and snow in the background or ledes suggesting colder weather ahead. Some of the more duplicitous jerks will continue to use that material, even after it has been shown to be faked or grossly out of context.
In short, the 1970s global cooling myth is a carefully crafted, well-layered, intentional whopper purely intended to mislead people who are, for the most part, honestly seeking legit information.
But consider that it's taken you at least ten minutes to slog through this post, follow the dots, and see how they connect in a nice, crooked path of deception? Add in that this spiel is particularly effective on people now in their 40s and 50s, because we remember the fascinating articles in venues like Newsweek and Time, and our local newspapers that glommed onto them, about impending ice ages from when we were kids. But it only takes a few seconds to quip that climate scientists in the '70s were predicting an imminent ice age, so they obviously know jack-shit about future climate. And now you understand why the oily propaganda ministers just can't help themselves, even though the precise anatomy of this particular zombie lie has been laid out in exquisite detail at their feet time and time again going on a decade now.
