Climate is a complex thing.
It undergoes periodic shifts. Surprisingly, even very slight changes in overall temperature can have significant impact on the daily lives of ordinary people. This can be easily illustrated by what is known as the Little Ice Age, a relatively recent epoch in world history. During the Little Ice Age, the average change in temperature over the globe was only a one degree Celsius decrease. And yet the world was altered in significant ways.
Although there is some disagreement on precisely when it started, it seems to have been at its worst from the 1500s through about 1850. Some suggest it began about 1250 when the Atlantic pack ice began to grow. Others place its beginning in the 1550s when glaciers began expanding around the world.
The Little Ice Age brought bitterly cold winters to most of the world. The population of Iceland dropped by half. During the winter the sea ice extended for miles in every direction around that island, cutting it off from all shipping. The settlements in Greenland that had been established centuries earlier by the Vikings were abandoned because they could no longer grow sufficient food. In the mid 1600s glaciers in the Swiss Alps advanced, slowly swallowing up farms and crushing whole villages. In England, the Thames regularly froze over in the winter (something it doesn’t do today). Likewise, the canals and rivers of the Netherlands often froze, with people regularly skating on them and holding frost fairs on the ice. The first frost fair in England on the Thames occurred in 1607. The last was held in 1814. In 1780 New York Harbor froze, allowing people to walk from Manhattan to Stanten Island.
Crop practices throughout Europe changed; the growing season became unreliable and in fact, on not a few occasions summer simply didn’t come. There are records of snowfalls in July and August in parts of Europe during the Little Ice Age. In fact, 1816 is called the Year Without a Summer. In May of that year frost destroyed the crops that had been planted. In June, there were two large snowstorms in eastern Canada and New England. Many people died. There are records of ice in lakes and rivers as far south as Pennsylvania in July and August. The Year Without a Summer inspired Lord Byron to write his 1816 poem, Darkness. The novel Frankenstein was written by Mary Shelley when the constant rainfall of that cold, wet summer forced her and her friends to stay indoors during their vacation in Switzerland. They decided to see who could write the scariest story. The lack of oats to feed horses—thanks to the bad weather—may have inspired Karl Drais, a German inventor, to research new ways to achieve horseless transportation. He invented the velocipede, the ancestor of the modern bicycle.
Why did the Little Ice Age occur? The Year Without a Summer may have been due to a volcanic eruption that occurred from April 5 to 15, 1815 on the island of Sumbawa in what is today Indonesia. The eruption was the largest the world had seen in 1600 years and it threw enormous quantities of dust into the upper atmosphere, reducing sunlight.
The eruption also happened to occur during what is called the Dalton Minimum, a period of very low sunspot activity that stretched from 1790 to 1830. And, in fact, the worst period of the Little Ice Age corresponds to the time of the Maunder Minimum, which lasted from 1645 to 1715. While no physical link between low sunspot activity and cooling temperatures has been established, the coincidence of the Maunder Minimum with the worst part of the Little Ice Age has led some scientists to hypothesize a connection. For instance, during one thirty year episode within the Maunder Minimum, astronomers observed only about 50 sunspots, as opposed to a more typical 40,000–50,000 spots that should have been observed during that time. It is also worth noting that the gradual warming of the world since 1850 corresponded to an increase in solar sunspot activity.