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We can deduce that there was "an extended period of volcanic activity," one that — like emitting greenhouse gases from fossil fuels — "put all kinds of stuff up on the stratosphere..."
Nor were reduced sunspot activity and increased volcanic activity alone in causing the Little Ice Age. In the early 20th century, Serbian scientist Milutin Milankovitch speculated that as Earth's position relative to the Sun changes, there are long-term and cumulative effects that alter Earth's climate. This is now known as the Milankovitch Effect.
"What happened is that, if you look back at Earth's history over the past 2000 years, we were in a period where because of changes in Earth's tilt, there was an overall global cooling going on," Serreze observed. "And that turned around right around the mid-to-end of the 19th century to the warming that we see today."
Yet there is also a fourth factor that Serreze lists in addition to solar activity, volcanic activity and changes in the Earth's orbital geometry. It all comes down to the Atlantic Meridional Overturning Circulation, or AMOC for short. This system of ocean currents — which is also being destabilized by climate change — includes one "belt" of ocean water that flows north and is warm, so that upon reaching the northern Atlantic it cools and evaporates. While that happens, AMOC causes the water in that region to become saltier and therefore both colder and heavier, sinking and flowing south to create a second belt. These two currents are connected by other oceanic features in the Labrador Sea, the Nordic Sea and the Southern Ocean.
In terms of modern climate change, the ongoing concern is that if AMOC slows down too much or stops entirely, temperatures in Europe will plummet to Little Ice Age levels and the number of extreme storms all over the world will increase. As for the Little Ice Age, "there is evidence from ocean cores and things like this that that overturning circulation may have been disrupted somehow so that it wasn't bringing the warmth into Northern Europe that it normally would."
Lapointe also added a new interesting hypothesis to understanding what exacerbated the Little Ice Age — namely, that Western colonization of the American continents played a significant role.
The logical fallacy committed by those who sincerely believe that the Little Ice Age disproves climate change is that, because humans were not responsible on that particular occasion, they assume this means they could not be responsible today.
"On a more speculative yet interesting hypothesis is the 'Great Dying' of the Americas," Lapointe argued. "In 1492, Christopher Columbus reached the Americas, initiating a significant period of European exploration and colonization. Over the ensuing decades, Europeans encountered Indigenous American populations, leading to conflicts, violence and the introduction of deadly diseases. Among the most devastating diseases brought by Europeans was smallpox, which resulted in the deaths of millions of Indigenous Americans, causing immeasurable tragedy and loss of life."
The hypothesis, Lapointe asserted, is that in addition to the horrors of the Western genocide against indigenous peoples, "the colonization process may have had unintended ecological ramifications with potential climate implications. Many Indigenous American communities were skilled farmers who practiced land cultivation and clearance for agricultural purposes. The arrival of European colonists disrupted these established farming practices, leading to depopulation in certain regions."
Since the forests were left untended, the hypothesis holds that "the reforestation following the decline of Indigenous American populations might have resulted in a temporary drawdown of carbon dioxide from the atmosphere. The increased forest cover could have absorbed CO2 through photosynthesis, thus contributing to a cooling effect on the planet," Lapointe said.
If there is one consistent lesson that can be drawn from what science tells humans about the Little Ice Age, it is that the climate is a delicate combination of elements that can be dramatically changed by outside variables. Perhaps the logical fallacy committed by those who sincerely believe that the Little Ice Age disproves climate change is that, because humans were not responsible on that particular occasion, they assume this means they could not be responsible today. Yet that mindset is inherently unscientific, according to anthropologist Brian Fagan, who wrote a 2000 book called "The Little Ice Age" and is professor emeritus of Anthropology at the University of California, Santa Barbara.
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