How An Amateur Meteorologist Set Off A Climate Change Firestorm — In 1938
The idea of global warming had already been theorized, but Guy Callendar showed it was already happening.
In 1938, a British engineer and amateur meteorologist made a discovery that set off a fierce debate about climate change.
Scientists had known for decades that carbon dioxide could trap heat and warm the planet. But Guy Callendar was the first to .
He showed that land temperatures had increased over the previous half-century, and he theorized that people were unwittingly raising Earth鈥檚 temperature by burning fossil fuels in furnaces, factories and even .
When Callendar , it set off a firestorm. The scientific establishment saw him as an outsider and a bit of a meddling gentleman scientist. But, he was right.
His theory became widely known as 鈥渢he Callendar Effect.鈥 Today, it鈥檚 known as global warming. until his death in 1964, increasingly bewildered that the science met such resistance from those who did not understand it.
A theoretical basis for climate change had been developed over the 114 years leading up to Callendar鈥檚 research.
Scientists including , , and had developed an understanding of how water vapor in the Earth鈥檚 atmosphere trapped heat, noted that carbon dioxide in the atmosphere also absorbed large quantities of heat and speculated about how increasing fossil fuel use could raise Earth鈥檚 temperature and change the climate.
However, these scientists spoke only of future possibilities. Callendar showed global warming was already happening.
An Engineer Runs His Own Climate Experiments
Callendar received a from City and Guilds College, London, in 1922 and went to work for his father, a well-known British physicist. The two shared interests in physics, motorcycles, racing and meteorology.
Callendar would later join the U.K. Ministry of Supply in armament research during World War II and continued to conduct war-related research at Langhurst, a secret research facility, after the war.
But his climate change work was done on his own time. Callendar kept journals with detailed weather data, including carbon dioxide levels and temperature. In an , he claimed there was an 鈥渋ncrease in mean temperature, due to the artificial production of carbon dioxide.鈥
He averaged diverse sets of temperature data from all over the world, primarily using the Smithsonian publication 鈥淲orld Weather Records,鈥 and derived global average temperatures that .
He also calculated how much carbon dioxide humans were putting into the atmosphere 鈥 the annual net human addition. In 1938, it was about 4.3 billion tons, which for that year of about 4.2 billion tons. Note that global carbon dioxide emissions in 2018 were .
Gathering published data on carbon dioxide levels in the atmosphere, Callendar created a graph correlating temperature increases over time with increases in atmospheric carbon dioxide levels.
What Callendar Discovered
Perhaps most importantly, Callendar recognized that new data on the heat absorption of carbon dioxide at meant that adding carbon dioxide would trap more heat than water vapor alone.
In the period before Callendar鈥檚 paper, key scientists thought the huge volume of , one of the 鈥済reenhouse鈥 gases that keep Earth warm, would dwarf any contribution by carbon dioxide to Earth鈥檚 heat balance. However, heat is radiated out to space as waves, with a range of wavelengths, and water vapor absorbs only some of those wavelengths. Callendar knew that recent, more precise absorption data showed that carbon dioxide absorbed heat at wavelengths that water missed.
After Callendar published his paper, global warming caused by human activities generating carbon dioxide was widely referred to as the 鈥.鈥滳allendar also considered different layers in the atmosphere. Carbon dioxide concentrates at a higher altitude in the atmosphere than water vapor. Atmospheric water vapor evaporates and then precipitates out of the atmosphere as rain or snow, but adding carbon dioxide severely upsets Earth鈥檚 energy balance because it stays in the atmosphere for hundreds of years. Carbon dioxide forms a heat trapping layer high in the atmosphere, absorbing heat that radiates upward from Earth鈥檚 surface and then emitting it back towards Earth鈥檚 surface. provided insight into this mechanism.
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However, his 1938 view was limited. Callendar did not foresee the magnitude of temperature rise that the world now faces, or the danger. He actually speculated that by burning carbon we might forestall 鈥 of the deadly glaciers.鈥
projected a 0.39 degree Celsius temperature rise by the 21st century. The world today is already than before the industrial era 鈥 three times the magnitude of the effect Callendar predicted.
Backlash To The Human Connection
The 鈥淐allendar Effect鈥 faced immediate resistance. Comments of initial reviewers questioned his data and methods.
The debate Callendar ignited . Temperature and carbon dioxide data, meanwhile, accumulated.
By the late 20th century, reviews of climate science held stark warnings about the path the world was on as humans continued to burn fossil fuels. The debate Callendar triggered is long since over.
Scientists from around the world, brought together by the United Nations and the World Meteorological Organization, have been reviewing the research and evidence since 1990. : The science is clear about . The danger is real and the effects of climate change are all around us.
Neil Anderson, a retired chemical engineer and chemistry teacher, contributed to this article.
This article is republished from under a Creative Commons license. Read the .
