The Scientific Road to Copenhagen

BERLIN – On June 10, 1859, six months before Charles Darwin published his 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 CO2. 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.”