Guy Callendar: Reflections on his biography.

The Callendar Effect – The Life and Work of Guy Stewart Callendar (1898–1964) The scientist who established the carbon dioxide theory of Climate Change in 1937.

Friends, as you may or may not know, Guy Callendar was the first person to discover that humanity’s emissions of carbon dioxide were measurably warming the Earth.

Astoundingly, he discovered this as an ‘amateur’ researcher in 1937, working part-time from his study in his modest home in Worthing.

His foundational paper on the discovery was published in 1938 and I wrote a précis of the paper earlier this year.

But since he lived his life as an establishment ‘outsider’, it was difficult to find out any information about his life on the web.

But last month I discovered that there is in fact a 2007 biography : The Callendar Effect by James Rodger Fleming. It arrived last week and I found reading the slim volume very moving.

So I thought I would just note down a few reflections. Please note, just about everything below is simply re-stating a few elements from James Rodger Fleming’s work.

Personal Life.

Guy Callendar was born in 1898, the third child of eminent polymath physicist and engineer, Hugh Callendar.

His father was a professor at Imperial College and Guy and his siblings had a privileged upbringing in what appears to have been an engineer’s dream household.

For example, in 1902 his father bought a motorbike, added an 8-speed gearbox and an ‘armchair’ to create a two-passenger tricycle allowing him and his wife to tour “the fearful hills of Porlock” and to treat the children to joy rides around the neighbourhood.

At age 5 his elder brother Leslie, for reasons undisclosed, “stuck a pin” in Guy’s left eye, blinding him in that eye.

He started at St Paul’s public school in 1913. His elder sister died of pneumonia in 1914, and with the start of the first world war, in 1915 he left school early.

Unfit for war service because of his blindness, he went to work for his father at Imperial College, using X-ray technology to search for defects in engine castings.

In 1919 he entered City & Guilds College – then part of Imperial – earning a certificate in Mechanics and Mathematics in 1922 – before starting work for his father on establishing the properties of steam at high temperatures and pressures. He continued this work intermittently throughout his life, and carried on the work after the death of his father in 1930.

In 1930 he married and a year later he and his wife Phyllis were “blessed” with twin daughters. He appears to have been a loving and devoted father and husband, enjoying family life, cycling, and tennis.

During and after the Second World War he worked at a secret establishment at Langhurst near Horsham on many topics but most significantly on the implementation of FIDO, a system for dispersing fog around runways.

He retired in 1958, and died of a heart attack in 1964

Throughout his life he seems to have been ‘modest and quiet’, not seeming to have been interested in advancement within the organisations within which he worked. I got the sense that he was perhaps something of a misfit, feeling most comfortable at home with his family.

Working for his father from an early age he would have been exposed to advanced ideas and technologies, but his credentials were built on practical knowledge rather than higher degrees and academic stature.


The chapter of James Rodger Fleming’s book on Callendar’s work on the climatic effect of carbon dioxide begins with a quote from Callendar himself.

“How easy it is to criticise, and how difficult to produce constructive theories of climate change

This seemed such a sad quote, because it was true in his own lifetime, when his work was initially dismissed by the meteorological establishment. Indeed during his lifetime his work was only recognised as significant within a very small circle.

And even 60 years after his death, with the climate change he predicted being seen as the greatest threat to humanity, and with his work having been validated a million times over, it is still commonplace for even otherwise well-educated people to criticise the theory without taking the effort to study it.

19th Century Insights & 20th Century Confusion

That the Earth’s surface is warmed by the atmosphere was not a new idea. In 1824 Jean Baptiste Joseph Fourier had written:

“The temperature of the Earth can be augmented by the interposition of the atmosphere, because heat in the state of light [i.e. visible light] finds less resistance in penetrating air than in re-passing into the air when converted into non-luminous heat [infrared light].

John Tyndall was, according to Callendar, the first to put forward the CO2 theory of Ice Ages. In the middle years of the 19th Century Tyndall demonstrated experimentally that:

“Perfectly invisible and colourless gases and vapours were able to absorb and emit radiant heat.

Around 1860 he wrote:

“The solar heat possesses… the power of crossing an atmosphere; but when the heat is absorbed by the planet, it is so changed in quality that the rays emanating from the planet cannot get with the same freedom back into space. Thus the atmosphere admits of the entrance of solar heat, but checks its exit; and the result is a tendency to accumulate heat at the surface of the planet.

Tyndall also concluded that:

“… changes in the amount of any radiatively active constituents of the atmosphere – water vapour, carbon dioxide, ozone or hydrocarbons – could have produced “all the mutations of climate which the geologists reveal… they constitute true causes, the extent alone of their operation remaining doubtful.

In 1896 Svante Arrhenius…

“…following Tyndall’s suggestion, demonstrated that variations in atmospheric CO2 concentration could have a very great effect on the overall heat budget and surface temperature of the planet and might trigger feedback phenomena that could account for glacial advances and retreats.

He later speculated…

“…on a ‘virtuous circle’ in which the burning of fossil fuels could help prevent a rapid return to the conditions of an ice age and could perhaps initiate a new carboniferous age of enormous plant growth.”

These 19th Century insights set the groundwork for Callendar’s work. But the first four decades of the 20th Century were filled with work which appeared to deny the possibility of the effect. One quote will suffice from the US Department of Agriculture in 1941:

“No possible increase in atmospheric carbon dioxide could materially affect either the amount of insolation reaching the surface or the amount of terrestrial radiation lost to space”

The Callendar Effect

Beginning around 1934, Callendar worked on his investigation of whether anthropogenic CO2 emissions were actively warming the Earth.  He begin this epic work in his study at home in Worthing.

Given his meagre resources I can only imagine his endeavours must have been all-consuming.

I find myself asking why it was Guy Callendar in particular that somehow pulled together all the parts of this complex problem and realised that the humanity was actually warming the Earth.

I think one part of the reason was that his eclectic experiences since an early age, and his lack of a well-defined academic role, probably allowed him to see the problem unconstrained by conservative meteorological views.

But his amateur status was probably (at least part) the reason why the meteorological establishment regarded his ideas with ongoing negativity.

In 1961, as he prepared for a summary publication of his ideas, he wrote a note listing “Reasons for the unpopularity of CO2 theory in some meteorological quarters“.

  1. The idea of a single (easily explained) factor causing world-wide climatic change seems impossible to those familiar with the complexity of the forces on which any and every climate depends.
  2. The idea that humanity’s actions could influence so vast a complex [system] is very repugnant to some.
  3. The metrological authorities of the past have pronounced against it, mainly on the basis of faulty observations of water vapour absorption, but also because they have not studied the problem to anything like the extent to required to pronounce upon it. 
  4. Last but not least. They did not think of it themselves!

But Callendar’s evident zeal for this project probably arose because of a profound understanding of the fundamental role of infrared light in establishing the temperature of the Earth, coupled with an understanding of the dynamics of CO2 in the atmosphere.

Additionally, he had worked extensively with the most accurate thermometers on Earth – developed by his father – and he was aware of the weaknesses and strengths of practical meteorological measurements.

In short, he had a uniquely eclectic combination of the necessary experience.

Together his insights led him to understand that increased atmospheric CO2 would inevitably warm the Earth independent of any degree of complexity in the details of atmospheric processes, and that that warming could be detected in spite of the difficulty.

His insights resulted a truly remarkable fact.

  • In 1937 using pencil and paper in his study, Callendar calculated that doubling the atmospheric concentration of CO2 would cause around ~1.5 °C of global warming.
  • In 2021 using resources beyond anything which Callendar might have imagined, and considering thousands of effects Callendar neglected, the IPCC 6th Assessment Report estimates that doubling the atmospheric concentration of CO2 would cause ~3°C of global warming with a likely range of 2.5°C to 4°C.

The similarity of these results is a testament to Callendar’s insight that the details don’t matter. This is analogous to the problem of putting an extra blanket on ones bed. Even though the heat transfer through woollen materials is complex, warming to some degree is inevitable.

A singular life

Ultimately, Callendar’s singular contribution to science has to remain something of a mystery. He produced an insightful work of genius in the most unlikely of circumstances.

But the slimness of his biography is indicative of a man who in many ways did not leave much of a trace, and his work was certainly not appreciated by many in his own lifetime.

But the slimness of the book also makes the little we know of his life even more poignant.


4 Responses to “Guy Callendar: Reflections on his biography.”

  1. David Edwards Says:
  2. Melissa Lord Says:

    Thank you for writing this thoughtful account, found via Twitter, and bringing to my attention Guy Callendar’s work.
    This is us poignant story – it will take me a while to work out the many layers of significance within it. So much to learn from, not just about his science, but also about the way that prestige speaks.
    Thank you, Protons.

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