Periodization in the history of science is governed by the appearance of certain texts: Newton (1687), Lavoisier (1789), Lyell (1833), Darwin (1859), Einstein (1905), Watson and Crick (1953). Knowing the names and dates, we can call off the titles of these works, all seen to initiate a new phase in the life of a given science. These foundational classics are seen to be built upon, but not overthrown. In climatology, such a foundational work is Köppen (1901): Versuch einer Klassification der Klimate, by Wladimir Köppen (1846-1940).
This text and its accompanying map defined what we mean by climate today-- suites of animals and plants living at different latitudes, in regions whose character is defined by mean temperature and precipitation. The system of climate zonation Köppen presented in 1901, and his scheme for mapping it, is still in use everywhere. Temperature and precipitation provide the threshold boundaries for suites of animals and plants that we now call indicator species; the shift in thermal and precipitation regimes at given latitudes, and the changing animal and plant communities at these same latitudes, constitutes what we mean by "climate change.” The “Köppen zones” and their associated species at the beginning of the 20th century function, to a very great extent, as the baseline climate for the modern world. Given scientific interest in climate change today, Köppen’s 1901 monograph has every right to be considered one of the most important scientific works of the last century.
