April 22: British scientist Guy Stewart Callendar became the first expert to link carbon dioxide emissions to global warming in a groundbreaking paper published on this day in 1938.
The renowned steam engineer was also the first person to acurately demonstrate that global land temperatures had increased over the previous 50 years.
But, counter to modern scientific thinking, Callendar believed this warming would be beneficial to humanity because it would help delay a “return of the deadly glaciers”.
His work went largely unnoticed at the time, although the Callendar Effect – as it was known for a short time – would help future climate scientists understand the change.
“In hindsight, Callendar's contribution was fundamental,” Dr Ed Hawkins, a climatologist at the University of Reading, said in a report published last year.
“He is still relatively unknown, but in terms of the history of climate science, his paper is a classic.
“He was the first scientist to discover that the planet had warmed by collating temperature measurements from around the globe, and suggested that this warming was partly related to man-made carbon dioxide emissions.”
Callendar’s research, published in Royal Meteorological Society’s journal, was an incredible feat for a man who considered climatology only an amateur interest.
His findings have since been shown to be remarkably accurate, which is an astonishing achievement given that he didn’t have a computer.
Callendar, the son of renowned British physicist Hugh Longboune Callendar, found that the world had heated by about 0.3°C between 1888 and 1938.
Compiling his report from his home in West Sussex, he suggested that about half this was due to the accumulation of carbon dioxide – or CO2 - in the atmosphere.
He performed his calculations by collecting temperature readings from 147 weather stations scattered over the planet and working out a global average.
However, Callendar, who was born in Montreal, Canada, had little or no data from the Arctic, Antarctica or the oceans, where recent studies have found the most warming.
Yet, despite scope for further tests, other climate experts at the time largely ignored Callendar’s findings and would remain sceptical for decades.
“Scientists at the time also couldn't really believe that humans could impact such a large system as the climate - a problem that climate science still encounters from some people today, despite the compelling evidence to the contrary, ” Dr Hawkins added.
It was only in the 1950s that experts began understanding the effect of carbon dioxide after new technology showed how the waste gas absorbed infrared radiation.
In 1963, experts from McGill University in Canada – filmed conducting tests in a British Pathé newsreel – showed that the icecaps were melting.
Yet many people remained sceptical about climate change, partly because the world did not warm further – and, for a brief period, land temperatures fell slightly.
Even after warming resumed in 1975, there continued to be doubts. But Scientific and public opinion began to change at the end of the 1980s.
British Prime Minister Margaret Thatcher, who had trained as a chemist at Oxford University, was the first global leader to voice alarm over climate change in 1988.
The same year, Americans also took notice when climatologist James Hansen told the U.S. Senate that global warming was to blame for a severe drought.
Since then, a raft of international deals – including the 1995 UN Kyoto Protocol – have been agreed to help combating climate change.
Nevertheless, the general public and many governments, while acknowledging the effect, are much less inclined to agree with scientists that man is to blame.
But the fact that any debate or further research into the matter has been carried out remains an enduring credit to the work of Callendar, who died aged 66 in 1964.