During Callendar’s later years (c.1950-1964) his CO2 climate warming theory was questioned by other climate scientists, who pointed to the undoubted complexity of global climate science and called for more research into factors such as the timescale of ocean-atmosphere exchange, deep ocean conditions and apparent discrepancies in the uptake of fossil fuel carbon. He continued his deep research (in a private capacity) and by the time of his death opinion was swinging strongly in his direction. As James Fleming concludes about this remarkable man:

“[His research judgment]] led him to conclude that the trend towards higher temperatures was significant, especially north of the 45th parallel: that the increased use of fossil fuels (and, to a lesser extent, deforestation and other practices) had caused a rise of the concentration of CO2 in the atmosphere that would only continue and would most likely accelerate; and that increased sky radiation from the extra CO2 was directly linked to the rising temperature trend. The world’s glaciers were shrinking, and he thought it unlikely that the oceans would absorb the excess carbon” [Callendar Effect, p.87].

Fleming goes on to say that most scientists now agree that Callendar was basically right, and that we now live in a world that has reached levels of atmospheric CO2 unknown to Callendar. 

Rising levels of CO2 in the atmosphere had been well documented by 1950. What was the effect?

“Reduced to its simplest terms…whereas CO2 is almost completely transparent to solar radiation, it is partially opaque to the heat which is radiated back to space from the earth [mainly due to the expansion of industry]. In this way it acts as a heat trap, allowing the temperature near the earth’s surface to rise above the level  it would attain if there were no CO2 in the air… It may be said that the climates of the world are behaving in a manner which suggests that slightly more solar heat is being retained in the atmosphere. This could be due to its increasing opacity to terrestrial heat as a result of the additions of CO2”

[Guy Callendar, “Can CO2 Influence Climate? ” Weather  4 (1949), pp. 310-314].

Despite Guy Callendar continuing to collect vital statistics on global warming, and publishing significant papers (such as one in 1961) his ideas met with dogged resistance from fellow meteorologists. Callendar explained this in a revealing note in his papers:

His fossil fuel theory was seen as too single-minded; ” the idea that man’s actions could influence so vast a complex [system] is very repugnant to some”; authorities in the past had pronounced against it, on the basis of faulty observations (which he had corrected); “Last, but not the least. They did not think of it themselves”.

Finally: ” CO2 as a cause of climate change… is above the heads of nearly all writers on the subject”‘

[from Fleming, Callendar Effect, pp.82-83] 

Guy Callendar wrote a game-changing paper in 1938 documenting rising global temperatures and linking this to the increasing burning of fossil fuels since the Industrial Revolution. Since 1900 humans had added over 150,000 million tons of CO2 to the air, and this was not dissipated in any of the ways that scientists had suggested (absorbed by oceans, circulation of the atmosphere, etc). He predicted a steady increase in temperatures in the century ahead.

However as James Fleming has pointed out, “Callendar was by no means an environmental alarmist, since he wrote of the benefits of the combustion of fossil fuels, including extension of the cultivated region northward, stimulation of plant growth by CO2, and the probable indefinite delay of the ‘return of the deadly glaciers’ “. [Callendar Effect].

Callendar’s thesis was for a time weakened by the fact that there was a period of relative cooling from the 40s to the 60s. Callendar himself became more seriously alarmed about disastrous future trends in climate change as he got older, and his “Callendar Effect” would go on to become a highly influential climate change theory.

In the 19th century great scientists such as John Tyndall and Svante Arrhenius anticipated greenhouse theory, arguing (in Tyndall’s words) that “rays from the sun and fixed stars could reach the earth through the atmosphere more easily than the rays emanating from the earth could get back into space” (1863) and that concentrations of CO2 could trigger feedbacks that would account for rising global temperatures (Arrhenius 1896). This in fact became conventional wisdom until critics in the early 20th century suggested other factors to explain climate change than human production of CO2. The critics included T. C. Chamberlin who pointed to changes in oceans as a key cause, Knut Angstrom, Charles Greely Abbott and F. E. Fowle who believed water vapour would absorb infrared radiation. By 1929 G. C. Simpson was able to say confidently that CO2 could have no real effect on climate. This became the orthodoxy until Guy Callendar strongly challenged it in 1939.

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“Guy Stewart Callendar (1898-1964) is noted for identifying, in 1938, the link between the artificial production of carbon dioxide and global warming. Today this is called the “Callendar Effect”. He was one of Britain’s leading steam and combustion engineers, a specialist in infra-red physics… and designer of the burners of the notable World War II airfield fog dispersal system, FIDO. He was keenly interested in weather and climate, taking measurements so accurate that they were used to correct the official temperature records of central England and collecting a series of worldwide weather data that showed an unprecedented warming trend in the first four decades of the twentieth century. He formulated a coherent theory of infrared absorption and emission by trace gases, established the 19th century background concentration of carbon dioxide, and argued that its atmospheric concentration was rising due to human activities, which was causing the climate to warm”:

[James Rodger Fleming, The Callendar Effect (2007), p. xiii}

see Paul website under Writings.

Gaia is “a complex entity involving the Earth’s biosphere, atmosphere, oceans and soil… the totality constituting a feedback or cybernetic system which seeks an optimal physical and chemical environment for life on this planet” [Lovelock’s definition].

“organisms interact with their inorganic surroundings on Earth to form a self-regulating, complex system that contributes to maintaining the conditions for life on the planet”.

Gaia was the Greek goddess of the earth, mother of all living things.

Here are some descriptions of the “Gaia Effect”, first put forward by James Lovelock in his book Gaia: A New Look at Life on Earth (1979) and many works since.

“All living things on earth (biosphere) function as one SUPERorganism that changes its environment to create conditions that best meet its needs, with the ability to self-regulate critical systems needed to sustain life”

“Over 4.6 billion years the Earth has become self-evolving, self-regulating, self-sustaining”.

The medical engineer ad earth scientist James Lovelock – still active and alert at 100 – became famous (or infamous) for his Gaia Hypothesis, which suggested that the earth was a self- regulating system (unless, as is now happening, it is threatened by dangerous human behaviours). As he defined it Gaia was “the totality constituting a feedback or cybernetic system which seeks optimal physical and chemical environment for life on this planet”.

He was attacked by some biologists (such as Richard Dawkins, whose views outside biology are to be treated with suspicion) for breaching natural selection theory, which Lovelock has robustly rebutted. He has not been helped by over-enthusiastic Greens, futurists and fantasy writers, who have taken his ideas to mystical heights. Lovelock modestly keeps proclaiming that he knows nothing about spiritualist things and is just an engineer trying to save the planet from environmental disaster.