In the early 19th century Joseph Fourier, a French pioneer in the study of heat, showed that the atmosphere kept the Earth warmer than it would be if exposed directly to outer space. By 1860 John Tyndall, an Irish physicist, had found that a key to this warming lay in an interesting property of some atmospheric gases, including carbon dioxide. They were transparent to visible light but absorbed infrared radiation, which meant they let sunlight in but impeded heat from getting out. By the turn of the 20th century Svante Arrhenius, a Swedish chemist, was speculating that low carbon-dioxide levels might have caused the ice ages, and that the industrial use of coal might warm the planet.
The Economist: The past, present and future of climate change
Sun shines from a cloudless sky in Kempten, southern Germany, where temperatures reached around 34 degrees Celsius on June 26, 2019.
