Distinctly Montana Magazine

67 w w w. d i s t i n c t l y m o n t a n a . c o m T HE LITTLE ICE AGE, WHICH PRIMARILY AF- FECTED THE NORTHERN HEMISPHERE, was the coolest and wettest period since, perhaps, the Younger Dryas event ended roughly 11,700 years ago. Depending on the criteria used to iden- tify its origin and geographical scope, climatol- ogists commonly interpret the Little Ice Age as a regime that lasted from ca. 1300 until the mid- or late 19th century. On the other hand, environmen- tal historians and anthropologists, especially those whose research focuses on the Plains culture area, typically frame the LIA more narrowly, limiting its boundaries to the Neo-Boreal period (1550-1850). Of the many factors that have been identified as possible contributors to the onset and duration of the Little Ice Age, two are particularly noteworthy. Sunspots, which are a visible indicator of fluctua- tions in the intensity of solar radiation, have been observed tele- scopically by astronomers for more than 400 years, as evidenced by Galileo's drawing on June 23, 1613. Lengthy periods of low sunspot activity, notably the Spörer (1460-1550), Maunder (1645-1715) and Dalton (1790-1830) minimums, correlate high- ly with both the coldest portions of the LIA and concentrated periods of explosive volcanism. A paleoclimatological study by Gifford Miller et al. (2012) presents a compelling argument that the first pulse of Little Ice Age cooling was triggered by a massive eruption of Mount Samalas (Indonesia) in 1257, followed closely by three large eruptions elsewhere during the late 13th century. Clive Op- penheimer (2011) concludes similarly that almost "half of the decadal variability seen in northern-hemisphere temperature reconstructions" for the period from 1400 to 1850 "can be at- tributed to volcanism." This correlation is particularly strong for the years from 1630 to 1850, when 16 major eruptions and cooling events oc- curred. Given the volatility of the Little Ice Age and Montana's reputation for extreme weather, an intriguing question comes to mind: Were conditions, particularly in winter, significantly more severe in Big Sky Country during the LIA than they are today? That question, unfortunately, cannot be answered definitively. The earliest instrumental and observa- tional data available for the Upper Mis- souri, including Montana, are ultimately attributable to Thomas Jefferson. Best known, of course, as America's third pres- ident, Jefferson also maintained a lifelong interest in meteorology. Indeed, his earli- est surviving weather observations were recorded at Philadelphia on those fateful days in early July 1776, when the Continental Con- gress formally adopted the Declaration of Indepen- dence. Twenty-seven years later, Jefferson instructed Meriwether Lewis to systematically document ther- mometric readings and weather observations on his forthcoming exploration of the Louisiana Territory. The Corps of Discovery did not enter pres- ent-day Montana until April 28, 1805, but journal entries made during the winter of 1804-1805 at Fort Mandan (North Dakota) chronicle the severity of conditions that existed then on the northern plains. They experienced a 13-inch snowfall on November 29, the coldest weather of their trip on December 17 (-45°F), and a ten-day period (January 5-14, 1805) during which overnight lows averaged -24°F. The accuracy of meteorological instruments from that era certainly can be questioned. Never- theless, Arlen Large compared thermometric data recorded by Lewis and Clark during January-March 1805 with the seasonal average for the same months from 1951-1980 at Bismarck, which is approximately 45 miles from the corps' encampment site. Large determined that temperatures at Fort Mandan were, on av- erage, eight degrees lower than corresponding values from the 20th century. Prince Maximilian of Wied compiled comparable data during the winter of 1833-1834 at Fort Clark, an American Fur Company post, located near the Mandan village of Mih-tutta- hang-kusch, in North Dakota. His most eye-popping comment, however, presents anecdotal data. On January 30, 1834, James Kipp, the post superintendent, returned to Fort Clark from Fort Union, where "the thermometer supposedly registered -45°F for more than fourteen days." Without an archival record consisting of instrumental obser- vations, paleoclimatologists utilize proxies, most commonly tree-ring and ice-core analyses, to reconstruct previous climate regimes. Brian Fa- gan, author of The Little Ice Age, observes that "Two cores from the Greenland ice cap, known as GISP- 1 and 2, are of particular interest [to researchers]. GISP-2 has an accura- cy in calendar years of ± 1 percent, which makes it exceptionally useful for dating temperature changes." Tree-ring studies, on the other hand, indicate that, from 1602-1900, winters on the plains were colder than those of designated 20th-cen- tury normal periods. The greatest temperature reduction, 5.6°F, was reported for the northeastern plains. Available evidence does not suggest by DOUGLAS A. SCHMITTOU illustrated by ROBERT RATH -45 0 f Thomas Jefferson

• Cover