The Little Ice Age and America’s Great Dying
Anybody who has been following the climate change file closely will have heard of the Maunder Minimum. It was a period between 1645 and 1715 when there was major decrease in sunspot activity, a phenomenon which is associated with a cooler sun.
And if you have heard of the Maunder Minimum in the context of climate change, then you will have heard of the Little Ice Age. In some circles, one was supposed to have caused the other. The trouble is that the Little Ice Age is a mighty big splash for such a small pebble.
Things that affect changes in climate are called climate forcings. Solar intensity is a climate forcing. When solar intensity goes down as it did during the Maunder Minimum, you can expect things to get cooler. The question is, how much cooler? How strong a climate forcing are we talking about? It turns out the effect is equivalent to 0.2 watts per metre squared of the Earth’s surface. That’s not enough to produce the effects recorded during the Little Ice Age. For comparison, the effect of greenhouse warming today is equivalent to 2 watts per metre squared, a factor of ten larger. Even admitting that climate change in the present century is more extreme (in the other direction) than the climate change represented by the Little Ice Age, a factor of ten is an awfully big difference in climate forcings.
To explain the Little Ice Age adequately, further causes need to be found. A possible one has been identified in a series of four volcanoes which erupted within 50 years of each other in the 1300s. The volcanoes sent particles into the atmosphere which temporarily blocked out sunlight, which, according to theory, caused more ice to form in the Arctic. This ice prolonged and extended the cooling effect of the volcanic aerosols, and, according to one climate model, sent icebergs down Greenland’s coast and introduced fresh meltwater into the Atlantic. This fresh water would not mix as well with salt water, a factor that would have interfered with ocean currents and impeded the flow of warm water from the Atlantic back to the Arctic, thus accelerating the build up of Arctic Sea Ice, etc. The Maunder Minimum could have fed into this system, adding another cooling factor into the one already underway.
Something else likely contributed too, carbon dioxide. Ice cores in Antarctica show that there was a decrease in carbon dioxide in the atmosphere between 1525 and the early 1600s amounting to 6 to 10 parts per million. What could have caused this sudden drop? Some scholars point to the effect of disease on the Americas following Columbus.
Many people don’t know about these most fateful of all epidemics. Before Columbus, the Americas lacked even the common cold. Diseases to which the people in the Americas had no immunity were introduced time after time by the European invaders. Smallpox had killed perhaps a third of Mexico City, and corpses already lay in piles on the causeways before Cortés came calling back with his armies. Some scholars have calculated that introduced epidemics following Columbus were responsible for eliminating 90% or more of the populations of the Americas, and often the plagues arrived out of European sight, the plagues moving ahead of the Europeans themselves, destroying communities and civilizations that the Europeans never had a chance to see or visit. Many of the so-called “empty lands” that the Europeans encountered had in fact been recently widowed. The effect was so devastating that even early European encounters with dense populations—on the West Coast of North America, in the Mississippi basin, in South America along the Amazon—were discounted by later historians because the people were largely gone by the time of a second visit.
The widowing of the Americas naturally had an effect on the ecosystems of the Americas, because the people who lived there had had a powerful effect which fell away when the people died. Forest lands that had been claimed by agriculture (most Aboriginal people were agriculturalists) were reclaimed by the forests. “Deer parks” created by Aboriginal people to facilitate hunting, opened up by the judicious and ongoing use of fire, filled up again. All of which resulted in more carbon dioxide being taken out of the atmosphere. Geochemist Richard Nevle estimated that an area as large as California was reforested as a result of the demographic disasters in the Americas. The new growth could have absorbed anywhere from 2 billion to 7 billion metric tons of carbon dioxide from the atmosphere.
The Big Chill in America—the death of 90% of the people in the hemisphere—brought about (or at least strongly contributed to) the big chill in Europe, the Little Ice Age. Nature engaging in literary metaphor. Now that’s something you don’t read about in the history books.
See also Charles C. Mann, 1493: Uncovering the World Columbus Created (Alfred A. Knopf, 2011.)