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French physicist Joseph Fourier was the first to document the greenhouse effect. Fourier suggested in 1824 that the Earth stays warm at night because its atmosphere traps sun-warmed gases in the same way that a greenhouse holds heated air - hence “greenhouse gases”.
In 1896, Swedish physical chemist Svante Arrhenius predicted that, if levels of carbon dioxide in the atmosphere doubled, the average temperature of the Earth would rise between 1.6 and 2.1 degrees Celsius. Arrhenius was later involved in setting up the Nobel Institutes and the Nobel Prizes.
But not every scientist agrees that the world is undergoing anthropogenic (man-made) warming. In fact, in the 1970s, climate scientists debated whether the globe might be warming or cooling. They were not sure.
Time magazine for June 24, 1974 declared: "However widely the weather varies from place to place and time to time, when meteorologists take an average of temperatures around the globe they find that the atmosphere has been growing gradually cooler for the past three decades."
The debate moved into the public domain at about the time of the Kyoto Protocol on climate change in 1997.
But why the focus on carbon dioxide? After all, it forms such a tiny percentage of Earth’s atmosphere. In fact, the Kyoto Protocol covers four greenhouse gases: carbon dioxide, methane, nitrous oxide and sulphur hexafluoride.
The Earth’s atmosphere is made up of about 78 percent nitrogen, 20 percent oxygen and 0.9 percent argon. That leaves 1.1 percent for everything else. In fact, the consensus is that, at the beginning of the 20th century, carbon dioxide accounted for about 280 parts per million in the atmosphere. That was 0.028 percent of the atmosphere!
How could a gas which takes up just 0.028 percent of our atmosphere cause our climate to warm?
On its own, it doesn’t, of course. There are the other greenhouse gases mentioned above and even water vapour. All make up tiny percentages of the atmosphere. Yet we should be grateful for them. Without them, Earth would be a frozen wilderness (first proposed by Joseph Fourier - see above). Scientists can calculate the amount of heat that reaches planet Earth from the Sun. It is not a lot; not enough to sustain life as we know it. So the greenhouse gases help to capture the heat radiated by the Sun and hold it in the troposphere, the layer of the atmosphere closest to the surface of Earth. Those gases might be poorly represented in the atmosphere, but they pack a punch.
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