A. E. Douglass

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A. E. (Andrew Ellicott) Douglass (July 5, 1867, Windsor, Vermont – March 20, 1962, Tucson, Arizona) was an American astronomer. He discovered a correlation between tree rings and the sunspot cycle.

"Douglass tracked this into past centuries by studying beams from old buildings as well as Sequoias and other long-lived trees. Noting that tree rings were thinner in dry years, he reported climate effects from solar variations, particularly in connection with the 17th-century dearth of sunspots that Herschel and others had noticed. Other scientists, however, found good reason to doubt that tree rings could reveal anything beyond random regional variations. The value of tree rings for climate study was not solidly established until the 1960s." [1]

Douglass founded the discipline of dendrochronology, which is a method of dating wood by looking at the growth ring pattern. He started his discoveries in this field in 1894 when he was working at the Lowell Observatory. During this time he was an assistant to Percival Lowell and William Henry Pickering, but had a falling-out with them, when his experiments made him doubt the existence of artificial "canals" on Mars and visible cusps on Venus

A crater on Mars is named in his honor.