Scientists have known for decades that carbon dioxide can trap heat and warm the planet. But Guy Callendar was the first to link human activities to global warming.
He showed that Earth’s temperatures had risen over the previous half-century, and he theorized that people were unwittingly raising the Earth’s temperature by burning fossil fuels in ovens, factories, and even his well-known motorcycles. loved.
When Callendar published his findings, it sparked a firestorm. The scientific establishment viewed him as an outsider and somewhat of an indiscreet scientific gentleman. But, he was right.
His theory became widely known as the “Calendar Effect”. Today, this is called global warming. Callendar defended his theory until his death in 1964, growing baffled that science met with such resistance from those who did not understand it.
The theory – A theoretical basis for climate change had been developed over the 114 years prior to Callendar’s research.
Scientists including Joseph Fourier, Eunice Foote, John Tyndall and Svante Arrhenius had developed an understanding of how water vapor in Earth’s atmosphere trapped heat, noted that carbon dioxide in the atmosphere absorbed also large amounts of heat and have speculated about how the increase in fossil fuels its use could raise the Earth’s temperature and alter the climate.
However, these scientists were only talking about future possibilities. Callendar showed that global warming was already happening.
Who was Guy Callendar?
Callendar received a certificate in mechanics and mathematics from City and Guilds College, London in 1922 and went to work for his father, a well-known British physicist. The two share interests in physics, motorcycles, racing, and meteorology.
Callendar would later join the British Ministry of Supply in weapons research during World War II and continued to conduct war-related research at Langhurst, a secret research facility, after the war.
But his work on climate change was done in his spare time. Callendar kept logs with detailed weather data, including carbon dioxide levels and temperature. In an innovative article published in 1938, he claimed that there was an “increase in the average temperature, due to the artificial production of carbon dioxide”.
He averaged various temperature data sets from around the world, primarily using the Smithsonian publication “World Weather Records”, and derived global mean temperatures that match current estimates of mean temperatures at the time very well.
He also calculated how much carbon dioxide humans were releasing into the atmosphere – the annual net human intake. In 1938 it was about 4.3 billion tons, which compares well with current estimates for that year of about 4.2 billion tons. Note that global carbon dioxide emissions in 2018 were around 36 billion tons.
By collating published data on carbon dioxide levels in the atmosphere, Callendar created a graph correlating increases in temperature over time with increases in atmospheric carbon dioxide levels.
Discovery – Callendar acknowledged that new data on the heat absorption of carbon dioxide at different wavelengths than water vapor meant that adding carbon dioxide would trap more heat than water vapor. water alone.
In the run-up to Callendar’s paper, leading scientists believed that the huge volume of water vapor in the atmosphere, one of the greenhouse gases that keeps the Earth warm, would dwarf any contribution from carbon dioxide. carbon in the Earth’s heat balance. However, heat is radiated out to space as waves, with a range of wavelengths, and water vapor only absorbs a portion of these wavelengths.
Callendar knew that recent and more accurate absorption data showed that carbon dioxide absorbed heat at wavelengths that water lacked.
Callendar also considered different layers of the atmosphere. Carbon dioxide concentrates at a higher altitude in the atmosphere than water vapour. Atmospheric water vapor evaporates and then rushes out of the atmosphere as rain or snow, but the addition of carbon dioxide severely upsets Earth’s energy balance because it remains in the atmosphere for hundreds of years. Carbon dioxide forms a heat-trapping layer in the atmosphere, absorbing heat that radiates upward from the Earth’s surface and then radiates it back to the Earth’s surface. Callendar’s article gave an overview of this mechanism.
After Callendar’s publication of his paper, global warming caused by human activities generating carbon dioxide has been widely referred to as the “Calendar effect”.
However, his 1938 vision was limited. Callendar had not anticipated the scale of the temperature rise the world is currently facing, nor the danger. He actually hypothesized that by burning carbon we could prevent “the return of the deadly glaciers”.
His paper predicted a temperature increase of 0.39 degrees Celsius by the 21st century. The world today is already 1.2 degrees Celsius (2.2 Fahrenheit) warmer than before the industrial age, three times the magnitude of the effect predicted by Callendar.
The backlash — The “Calendar effect” met with immediate resistance. Comments from initial reviewers questioned his data and methods.
The debate triggered by Callendar continued for the rest of the 20th century. Temperature and carbon dioxide data, meanwhile, accumulated.
At the end of the 20th century, journals of climate science contained stark warnings of the path the world was on as humans continued to burn fossil fuels. The debate triggered by Callendar is long over.
Scientists around the world, convened by the United Nations and the World Meteorological Organization, have been reviewing research and evidence since 1990. Their reports confirm: The science is clear on the role of humans in climate change. The danger is real and the effects of climate change are already evident all around us.
This article was originally published on The conversation by Sylvia G.Dee at rice university. Read the original article here.