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The year was 1800. Sir Frederick William Herschel (1738-1822) sat in his laboratory deep in concentration. He would discover one of the great mysteries of science — heat from light you can’t see.

Sunlight could warm a room. A prism would break sunlight into a spectrum of colors, but Herschel wondered if the different colors would have different heating properties. That question seems so simple today, but it marked the beginning of a completely new field of scientific investigation.

Light splitting into the visible spectrum. (Photo via WikiMedia Commons)

Light splitting into the visible spectrum. (Photo via WikiMedia Commons)

Herschel passed sunlight through a prism and then placed a thermometer in each band of color. He moved the thermometer to each band starting from violet. Each band was progressively warmer. Then something amazing happened.

Herschel placed the thermometer just outside of the red band. There was no visible light there but the thermometer continued to rise. Was there light that we can’t see? There must be. That invisible band had the property of producing more heat than any of the visible bands of color. This was the first time anyone had proven that there were types of light (or radiation) human eyes cannot see.

Today we know that 99.9 percent of the energy driving our climate comes from the sun. It’s the invisible infrared light that prevents Earth from being a frozen wasteland. How this happens was the next big mystery.

View from Rothera Research Station (on Adelaide Island) over Laubeuf Fjord, Antarctica. (Image Credit: Vincent van Zeijst)

View from Rothera Research Station (on Adelaide Island) over Laubeuf Fjord, Antarctica. (Image Credit: Vincent van Zeijst)

By the middle of the 1800s another breakthrough explained how radiant energy is captured by certain gases.

In 1824, French mathematician and physicist Joseph Fourier proposed the idea that something in the atmosphere must be preventing the heat from escaping the atmosphere. He suggested that our atmosphere must act like a box with a glass lid, like a greenhouse. This is not what actually happens, but the greenhouse metaphor caught on.

During the Victorian era, science was becoming the “in thing.” The study of physics and chemistry had made considerable progress. There was a better understanding of the states of matter. We knew that respiration and combustion used oxygen to produce carbon dioxide. The sun heats the earth, but why doesn’t all the heat return to space? Science was finally ready to answer that question.

Deep in the basement of the Royal Institution in central London, a 38-year-old, self-educated Irishman named John Tyndall came up with a means of measuring the capacity of water vapor and CO2 to capture radiant energy (heat) from sunlight. On May 18, 1859, he wrote in his journal: “Experimented all day; the subject is completely in my hands!”

Tyndall found that infrared energy could be captured by some gases and increase the temperature of the atmosphere.

Illustration of John Tyndall's setup for measuring the radiant heat absorption of gases. Appears in John Tyndall's 1872 book "Contributions to Molecular Physics in the Domain of Radiant Heat."

Illustration of John Tyndall’s setup for measuring the radiant heat absorption of gases. Appears in John Tyndall’s 1872 book “Contributions to Molecular Physics in the Domain of Radiant Heat.”

His apparatus was elegant. It consisted of a long vacuum tube with a infrared light source at one end and a thermometer at the other. Inside the tube he added water vapor. It turned out that water vapor did capture the energy and re-radiate it as heat. He repeated this experiment with CO2 and found that it also captured energy and re-radiated it as heat, though not as powerfully as water vapor. Not all gases he tried had this characteristic but water vapor and CO2 were clear winners. He found that increasing their concentration also increased the heat. Imagine how mysterious this must have seemed because he was working with something no one could see but nonetheless could be measured.

The “greenhouse effect” was not like the glass lid Fourier had described. “Greenhouse gases” are responsible for our comfortably warm planet. Tyndall immediately realized his discovery must have implications for Earth’s climate.

Carbon emissions from the Fisk Generating Station in Chicago, Illinois. (Photo Credit: Señor Codo / Fisk)

Carbon emissions from the Fisk Generating Station in Chicago, Illinois. (Photo Credit: Señor Codo / Fisk)

Science was still to determine how much influence greenhouse gases had in warming the atmosphere.

This task fell to Svante Arrhenius (1859-1927), a brilliant Swedish scientist, Nobel Laurate, and one of the founders of the science of physical chemistry. He was the first to attempt to estimate how much the climate would change for a given amount of CO2. He is often referred to as the first climate modeler. He devised a model of the Earth’s atmosphere and attempted to determine how much warming would take place if the CO2 concentration were doubled. His calculations were amazingly accurate considering there were no supercomputers in those days. What he couldn’t anticipate was the explosion in population and emissions from industrial expansion.

Over the next century, atmospheric science was expanded. More sampling was possible. Accuracy was improved. National Academies of Science were established around the world. The World Meteorological Organization (WMO), NASA, NOAA, The United Nations Environmental Programme; and The U.S. EPA were formed. In 1960, the first of dozens of climate and Earth monitoring satellites were launched. Hundreds of other government, academic and private institutions focused on greenhouse gases and a changing environment. Every year an ugly realization came into clearer focus.

Bert Bolin (1925-2007) was a pioneer in climate research and international policy. His work in the 1950s on the carbon cycle is relevant today. He was the founding chairman of the United Nations Intergovernmental Panel on Climate Change (IPCC) – today recognized as the most authoritative source of information on climate change and its effects. He served as chairman of the IPCC from 1988 to 2007.

Image Credit: Data source: Carbon Dioxide Information Analysis Center

Image Credit: Data source: Carbon Dioxide Information Analysis Center

The IPCC is formed by the U.N. Environment Programme and the World Meteorological Organization. The IPCC does not conduct research, but as a scientific body of internationally nominated experts, it assesses “on a comprehensive, objective, open and transparent basis the latest scientific, technical and socioeconomic literature produced worldwide relevant to the understanding of the risk of human-induced climate change, its observed and projected impacts and options for adaptation and mitigation.”

In 2007 the IPCC and Al Gore received the Nobel Peace Prize, “for their efforts to build up and disseminate greater knowledge about man-made climate change, and to lay the foundations for the measures that are needed to counteract such change.”

The history of climate science (link is more comprehensive than this article) has evolved from the first time we felt the sun’s rays to the study of quantum mechanics today. Step by step we have learned about Earth’s climate. Today the anthropogenic cause of global warming is no longer conjecture but fact.

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