LONDON, England (CNN) -- Climatology was once a small and often overlooked branch of science. But important discoveries made as early as the 19th century have contributed to what is the most important field of scientific study in the world today. Listed below are some key dates in climate change history.1824French physicist Joseph Fourier is first to describe a "greenhouse effect" in a paper delivered to Paris's Académie Royale des Sciences.1861Irish physicist John Tyndall carries out research on radiant heat and the absorption of radiation by gases and vapors including CO2 and H2O. He shows that carbon dioxide can absorb in the infrared spectrum, and it can cause a change in temperature. Tyndall famously declares: "The solar heat possesses. . . the power of crossing an atmosphere. But when the heat is absorbed by the planet, it is so changed in quality that the rays emanating from the planet cannot get with the same freedom back into space. Thus the atmosphere admits of the entrance of the solar heat, but checks its exit. The result is a tendency to accumulate heat at the surface of the planet.