Guy Stewart Callendar

The pause in the study of anthropogenic global warming continued for a surprisingly long time. After the first decade of the 20th century, it fell out of favor---and anyway seemed like a problem for thousands of years down the road. But there was one who thought differently.

Guy Stewart Callendar (1898-1964) was not a meteorologist. Or a climatologist. Or a physicist. In fact he was not a scientist of any kind! And a lot of his work was really flimsy. That was not all his fault---there was still no way of measuring carbon dioxide with the sort of pinpoint accuracy that we see today from Mauna Loa and other sites. But he was the only one who made any sort of impact at all during the long period of inactivity in greenhouse studies, so he is worth going over.

Callendar was the son of a prominent British physicist, Hugh Longbourne Callendar, and Victoria Mary Stewart. Hugh Longbourne Callendar specialized in thermodynamics, and held the lead physics chair at McGill University from 1893-1898. So Guy Stewart Callendar was born in Montreal. Hugh Callendar did make one innovation outside of thermodynamics---he developed and implemented the idea of using X-rays to inspect machine parts. He started with aircraft engines in World War I, helping to discover hidden defects and making engine manufacturing more efficient, by revealing how and where defects occurred---enabling manufacturing processes to be revised to lower defects and increase efficiency.

Back to Guy Callendar. As I said, he was not a scientist---although he stayed in the general field of his father. Guy was a power plant engineer, and he was a good one. From the 1920s on he developed methods to make energy production more efficient--which obviously required a good working knowledge of thermodynamics. He was also an amateur meteorologist. Well, not really. He didn't have a lot of training, although he read a lot of work in meteorology. But he never obtained a degree or took advanced coursework. And he was convinced the world was warming. And he was right about that. He was also convinced that mankind's CO2 emissions were responsible. About that, he was not right. At least not yet.

[It has to be said here that CO2 emissions, while rising rapidly from the 1870s on, were rising from a very low base, compared to today. By the 1920s and 1930s, CO2 emissions were just enough to have a very slight effect on climate, especially if sustained. However, they were not enough to account for the warming that took place from the 1880s to the 1930s, which must therefore have mostly resulted from natural causes.]

Whatever the causes, the warming was noticed by the 1920s and 1930s. Arctic ice shrank. Warming was most pronounced over the Arctic (Antarctica had no good weather records---expeditions kept meteorological diaries, but no permanent bases were established until the 1957-1958 International Geophysical Year, and there was only the testimony of the whalers who talked of "good ice years" and "bad ice years" and almost NEVER braved the Antarctic winter.

The warming was also most noted in continental interiors and less in the oceans--exactly what Arrhenius had predicted!

[This is also questionable. Callendar was basing this on the Dust Bowl drought of the 1930s, with the record heat waves in 1934 and 1936. Stalin's Soviet Union was not cooperating with other countries in releasing meteorological information. There was also political pressure on climate statistics there. Stalin and the Lysenko clique believed that the development of Siberia---the growth of cities and the leveling of the forests would result in a warmer climate. The point was made when meteorologists were executed when their records showed that the temperature had dropped from one year to the next. Temperature records therefore showed steady rises from year to year. This data was not released to the world, being a 'state secret'. Mongolia of course did not have regular meteorological observations that could be used to determine climate well. Republican China had a few places with reliable observations--Beijing, Shangghai, Hong Kong. But the Chinese did not have reliable climatic records for the interior.]

So on the basis of temperature records in Spitsbergen, Greendland, the Canadian Arctic, and the United States, Callendar concluded that anthropogenic global warming was occuring---and was occuring NOW (in the 1930s)

Callendar researched the levels of carbon dioxide in the atmosphere. The method for determining atmospheric CO2 concentrations was primitive, and not very accurate. What one did was get a dilute alkaline solution, and bubble air though it at a fixed temperature and rate and determined how much air flowed through before it neutralized the alkaline solution (CO2 being an acid compound). But this was fraught with difficulty. First of all, it assumed that all the CO2 in the air bubbling through the alkaline solution was interacting with it--what if some made it through? Second, observers did not always use the same alkaline compound---and we now know that CO2 reacts more easily with some basic compounds than others. Absorption of CO2, like all gases, varies according to temperature. The colder it is, the more easily the gas dissolves. And the apparatuses scientists used were not the same--each one tended to build his own apparatus (scientists being almost all male in those days--as far as I can tell, none of the pre-World War II observations were made by a woman)

There were also problems with local effects. The level of CO2 varies measurably between night and day. Downwind of herds of farm animals it was elevated. And observed CO2 levels in cities were very high--some of the observations in London during "pea soup" smogs when pollution was trapped under inversions were over 550 ppm! And those figures were probably correct. Greenwich Observatory reports figures over well over 500 ppm now during inversions.

Callendar was convinced that atmospheric CO2 was rising but it was almost impossible to prove. In fact, it was impossible, unless he made some arbitrary assumptions. First, he eliminated urban observations. Then he went over rural observations---and took out some downwind of large herds or in a couple of cases, power plants. After that, his decisions on what CO2 observations to include, and what not to include, seem mostly arbitrary. Callendar did include observations from ocean islands, like the Azores and Bermuda---and those were probably the best sites to observe what he was looking for. But his methodology was questionable. However in fairness, these primitive observations were all he had to work with.

Callendar wrote articles for science journals until the early 1960s, and here is his data reproduced from a late article. The observations he included when he made his presentation to the Royal Meteorological Society in 1938 are circled in the graph below.

As you can see, the observations Callendar chose do show a rising trend. And no one believed that the observations above 400 ppm were representative of the atmosphere of the Earth. But you can also see how there were a lot of observations Callendar excluded that seem like 'reasonable figures'.

Callendar was nervous as he addressed the Royal Meteorological Society. They listened politely. They did ask some questions about his choice of data. There was a little scattered applause when he finished.

And that was pretty much it. Callender published his work later in 1938 in the Journal of the Royal Meteorological Society. Callendar, G.S. (1938). "The Artificial Production of Carbon Dioxide and Its Influence on Climate." Quarterly J. Royal Meteorological Society 64: 223-40

After the questions about 'cherry picking' data and some correspondence with meteorologists, he omitted the graph above. His article contains some interesting statements, such as the one below:

"By fuel combustion, man has added about 150,000 million tons of carbon dioxide to the air during the past half century. The author estimates from the best available data that approximately three quarters of this has remained in the atmosphere."

n.b. At present we add that amount in 4 years.

Callendar believed that global warming would proceed at about 0.5C per century.

He believed that the concentration of CO2 in the atmosphere was 274 ppm before industrial activities began.

He believed that CO2 in 1936 was about 296 ppm.

Unlike Arrhenius, Callendar took into account economic growth. He believed that CO2 emissions were rising over time. So CO2 concentrations would go up faster and faster! But his estimates for the future seem quaint.

2000 AD 335 ppm
2100 AD 396 ppm (will probably be reached in 2012)
2200 AD 458 ppm (will probably be reached by 2060)

Callendar had some notions that were just plain wrong. We know that only about half of CO2 remains in the atmosphere. He also ignored the roles that convection and fronts have in redistributing heat in the atmosphere, and for this was roundly criticized.

But Callendar was also right in some ways. He believed that the oceans would not absorb all CO2 as it was emitted---pointing out correctly that if CO2 was absorbed so readily---then why was there any CO2 in the atmosphere at all? That caused many scientists some uneasiness--there must be some property of the ocean to resist absorbing CO2 to account for its presence.

Callendar was also right about the examination of CO2 absorption spectra and saturation. He argued that the behavior of CO2 infrared absorption in the cold dry upper levels of the atmosphere was not addressed by laboratory experiments at room temperature and pressure.

Callendar, G.S. (1941). "Infra-Red Absorption by Carbon Dioxide, with Special Reference to Atmospheric Radiation." Quarterly J. Royal Meteorological Society 67: 263-75.

However, most scientists believed Callendar was beating a dead horse there. Richard Russel, writing for the United States Department of Agriculture, pronounced that the absorption saturation was the "fatal flaw" in Callendar's argument. And that settled it for several years.

Russell, Richard J. (1941). "Climatic Change through the Ages." In Climate and Man. Yearbook of Agriculture, edited by United States Department of Agriculture. Washington, DC: US Govt. Printing Office.

For a non-meteorologist, Callendar's ideas did get a surprising amount of tolerance. Most meteorological textbooks of the 1940s and 1950s give him a short section, then rebuttals by meteorologists and physicists explaining why he was wrong. Callendar published many articles--but the general reaction of meteorologists at the time was to let him present his view, and address his ideas and answer his questions.

A short selection of more of his articles below:


Callendar, G.S. (1949). "Can Carbon Dioxide Influence Climate?" Weather 4: 310-14.

Callendar, G.S. (1958). "On the Amount of Carbon Dioxide in the Atmosphere." Tellus 10: 243-48.

Callendar, G.S. (1961). "Temperature Fluctuations and Trends over the Earth." Quarterly J. Royal Meteorological Society 87: 1-12.

Not everyone dismissed Callendar completely. Although the infrared radiation absorption saturation question was considered settled---the question of absorption of CO2 by the sea was not. It was well known that for every molecule of CO2 in the atmosphere, there were 50 in the sea. But then why didn't the sea absorb the 51st molecule?

Callendar thought that the oceans were stratified, that the surface layers did not mix readily with the deeper layers, and that the thin surface layer would be saturated quickly and not absorb more CO2. Harald Sverdrup, (1888-1957) perhaps the greatest oceanographer of the 20th century, and worthy of several blog entries himself, published his monumental work The Oceans: Their Physics, Chemistry and General Biology in 1942 and conclusively showed this was incorrect. The deep waters and surface of the oceans are exchanging readily.

So then what was keeping the oceans from absorbing all the CO2 in the atmosphere? No one was able to propose an acceptable mechanism for why the oceans would absorb CO2 until it reached 274 ppm and then stop.

Callendar lived long enough to see the first few years of the Mauna Loa readings taken by Charles Keeling. CO2 was accumulating in the atmosphere.

But that's for another blog entry.

Guy Stewart Callendar's picture: