What did scientists know and say about climate change and global warming in the 1970s? I keep running into claims by modern climate change denialists that scientists in the 1970s firmly predicted a pending ice age. This is usually posited to establish that scientists are fools, and that concerns about warming now are probably displaced because the same scientists were in error 40 years ago.
I worked in air pollution studies way back then. That’s not how I remember it at all. I remember great, good-natured debates between Ph.Ds in the Department of Biology at the University of Utah, and other scientists from other institutions passing through and working in the field with us. Greenhouse effect was very well understood even back then, and the discussions were on the nature of just how much human pollution would affect climate, and in which way.
Savvy scientists then well understood that there were two competing trends in air pollution: Greenhouse gases and particulates and aerosols. Greenhouse gases would warm the climate, but they were offset by particulates and aerosols that reflect solar radiation back into space before warming can occur. At least, back then, the particulates and aerosols counteracted the greenhouse gases.
Looking for something else I took off my shelf a book we used as a text in air pollution courses in the 1970s, Whatever Happened to Fresh Air? by Michael Treshow. Treshow taught at Utah. He was deeply involved in several research projects on air pollution. He was also a great conversationalist and competitive tennis player. His book was a good text, but he intended it to be read by lay people, especially policy makers, also. It’s easy to fathom, intentionally.
Here, below, is what Treshow wrote in the early pages about carbon dioxide as an air pollutant, in sketching the global problems of air pollution. Notice that, while he makes note of the predictions of what would happen with uncontrolled particulate and aerosol pollution, he gives the science straight up, telling what pollution can do, depending on local circumstances and global circumstances. Treshow notes the research that the denialists cite now, but he explains enough of the science so that any reasonable person should be able to see that, if one form of pollution is controlled and another is not, the effects might be different.
Over the past several million years, the earth’s animal and plant life have reached a workable equilibrium in sharing this atmosphere and keeping the oxygen and carbon dioxide concentrations in balance. But man, by burning fossil fuels (particularly coal) at an accelerated rate and by removing vegetation at the prodigious rate of 11 acres per second in the U.S., may be upsetting this equilibrium. Many scientists believe this carbon dioxide build-up is one of the major threats to man’s environment.
Carbon dioxide (CO2) is occasionally regarded as an air pollutant for this reason, even though it is a natural and essential component of the atmosphere. Certainly the present concentrations are not dangerous; but what would happen if the amount of carbon dioxide in the atmosphere should increase appreciably? What hazards would be imposed?
An increase in carbon dioxide would benefit the green plants since they need it for photosynthesis. But what effect would it have on man and animals? Or on the physical environment? The main hazard lies in the effect that carbon dioxide has in absorbing the infrared radiation which normally radiates from the earth back to the atmosphere. If the carbon dioxide content of the lower atmosphere were to increase, it would prevent the infrared heat absorbed by the earth from the sun from reradiating into the atmosphere. Heat energy would accumulate and cause a general increase in the earth’s temperature. Such an increase in temperature, often called the “greenhouse effect,” could cause the ice caps to melt, raising the level of the oceans and flooding most of the world’s major cities.
It is awesome to realize that sea level is actually rising. It is now 300 feet above what it was 18,000 years ago, and is reportedly rising nearly nine inches higher each century. Beaches are being wasted away and tides lap ever closer to the steps of coastal homes. But is the displacement of our beaches more closely related to increasing carbon dioxide concentrations or to the normal warming process between ice ages?
Not everyone agrees that carbon dioxide is to blame. Concentrations vary greatly around the world. Near urban areas, where fossil fuels are burned, concentrations are high; over forested areas, where plants are rapidly removing the gas, they are low. Concentrations also vary with the height above the ground, the latitude, whether over the ocean or land and even with the time of day and season of the year. All of these variables make it difficult to agree on a reasonable average carbon dioxide concentration.
Despite some disagreement, it is generally conceded that carbon dioxide has been added to the atmosphere at an alarming rate during the past century. Actual measurements show that between 1857 and 1956, carbon dioxide concentrations increased from an average of 0.0293 to 0.0319 percent; 360 X [10 to the 9th] tons of carbon dioxide have been added to the atmosphere by man during this period. Upwards of a trillion tons will be added by the year 2000. Such a tremendous release of carbon dioxide would increase the atmospheric concentrations appreciably unless some mechanism is available to absorb the surplus and to maintain equilibrium.
Extensive measurements suggest that carbon dioxide concentrations near the earth’s surface have increased about 10 percent since 1900. During this same time, fossil fuel consumption increased about 15 percent. This is a remarkably, close, meaningful relationship. The 5 percent difference is readily accounted for, since this much would be absorbed by the ocean or by rocks and living organisms, particularly plants, which absorb much of the surplus carbon dioxide. In fact, green plants probably have the capacity to absorb and utilize far more carbon dioxide than man is likely to release.
Calculations presented by Gordon MacDonald of the University of California at Santa Barbara show that a 10 percent increase in the total carbon dioxide content theoretically should cause an increase of 0.4° F in the average temperature of the earth. Although the carbon dioxide content is being increased about 0.06 percent each year by the combustion of fossil fuels, no temperature increase has been demonstrated. Rather, the average temperature appears to be decreasing. During the past 25 years, when the addition of carbon dioxide has been most rapid, the average temperature has dropped half a degree.
This temperature drop has been thought to result from the increase in the amount of submicron sized particulates which remain suspended in the atmosphere. These aerosols obstruct the entrance of the sun’s heat and light rays, thereby disrupting the earth’s energy balance. The effect is one of less heat and lower temperatures. Dr. William E. Cobb of the National Oceanic and Atmospheric Agency predicts the possibility of another ice age.
Whatever Happened to Fresh Air, Michael Treshow, University of Utah Press, 1971, pp. 3-6.
What changed since then? The Clean Air Act provided the legal drive to clean particulates and aerosols out of the air. Alas, we did not then have good controls for greenhouse gases. The success of the Clean Air Act, and similar laws worldwide, rather left the pollution field open for greenhouse gases. Without pollution to offset the effects of GHG, warming became the stronger trend.
I think Treshow was quite prescient back then. His work is still accurate, when we adjust for the events of history that came after he wrote the book.