On June 10, 1859, six months before Charles Darwin published his On the Origin of Species, the physicist John Tyndall demonstrated a remarkable series of experiments at the Royal Institution in London. The meeting was chaired by Prince Albert. But neither he, nor Tyndall, nor anyone in their distinguished audience could possibly have anticipated the extent to which the experiments’ results would preoccupy the world 150 years later.
This month, thousands of people from all over the world, including many heads of state, will gather in Copenhagen to try to forge an agreement to drastically cut atmospheric emissions of an invisible, odorless gas: carbon dioxide. Despite efforts by some leading countries to lower expectations ahead of the conference about what can and will be achieved, the meeting is still being called the most important conference since World War II. And at the conference’s heart are the results of Tyndall’s experiments.
But the story starts even before Tyndall, with the French genius Joseph Fourier. An orphan who was educated by monks, Fourier was a professor at the age of 18, and became Napoleon’s governor in Egypt before returning to a career in science. In 1824, Fourier discovered why our planet’s climate is so warm — tens of degrees warmer than a simple calculation of its energy balance would suggest. The sun brings heat, and earth radiates heat back into space — but the numbers did not balance. Fourier realized that gases in our atmosphere trap heat. He called his discovery l’effet de serre — the greenhouse effect.
It was Tyndall who then put Fourier’s ideas to the test in his laboratory. He proved that some gases absorb radiant heat (today we would say long-wave radiation). One of these gases was carbon dioxide.
In 1859, Tyndall described the greenhouse effect in beautifully concise words: “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.”
Then, in 1897, Svante Arrhenius, who earned a Nobel Prize for chemistry six years later, calculated how much global warming a doubling of carbon dioxide in the atmosphere would cause. His answer was 4ºC to 6ºC (a little more than the 2ºC to 4ºC degrees that modern studies consistently find).
Arrhenius was not in the least troubled by the prospect of global warming. Perhaps because he was Swedish, he proposed setting coalmines on fire to speed it up, since he thought a warmer climate was an excellent idea. But it was all just theory in Arrhenius’s time, since nobody had measurements to prove that carbon dioxide levels in the atmosphere were in fact increasing.
That changed only in the late 1950s, when Charles Keeling started to measure carbon dioxide with unprecedented accuracy in Antarctica and on Mauna Loa in Hawaii, far away from any sources. By 1960, he was able to prove that carbon dioxide was indeed on the rise.
It then took only a few years until, in 1965, an expert report — the first of many — to then US president Lyndon Johnson warned of global warming: “By the year 2000, the increase in carbon dioxide will be close to 25 percent. This may be sufficient to produce measurable and perhaps marked changes in climate.”
In 1972, a more specific prediction was made in the leading science journal Nature, namely that temperatures would warm by half a degree Celsius by 2000. And, in 1979, the US National Academy of Sciences issued a stark warning of impending global warming.
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