Christopher Columbus, the great explorer who brought the Old and New Worlds together, has been lauded in some quarters as a hero while attacked in others as a villain. Now, climate researchers have weighed into the debate, suggesting that Columbus’s arrival in the Americas may have touched off the Little Ice Age. Was Christopher Columbus a “Climate Change Villain?”
Did Christopher Columbus cause the Little Ice Age?
The Little Ice Age was a period of global cooling “that lasted from about A.D. 1550 to about A.D. 1850 in Europe, North America, and Asia.” It affected both Hemispheres and led to colder temperatures as well as increased ice formation. The Little Ice Age was characterized by crop failures, famine, hypothermia, strange weather patterns and bread riots. How in the world could a single explorer cause all that?
Well, it’s a pretty roundabout path, according to geochemist Richard Nevle. Prior to Christopher Columbus, some 40-100 million people lived in the Americas. They periodically burned vast swathes of land in order to farm crops, leaving large charcoal deposits in their wake.
Then Christopher Columbus arrived. While his own voyages were harmless, the same cannot be said of those of his successors. Europeans quickly followed in Columbus’s path. They sailed to the New World and set about colonizing it. It’s estimated that ~90% of the indigenous population died from either war or disease during this period.
The devastation left far fewer people to care for crops. Charcoal deposits vanished and trees began to grow in formerly-cleared areas. This new flora absorbed as much as 2-17 billion metric tons of carbon-dioxide in the process. The reduced levels of this greenhouse gas left the atmosphere unable to trap as much heat as in the past. And thus, the planet cooled.
“We have a massive reforestation event that’s sequestering carbon … coincident with the European arrival.” ~ Richard Nevle, Stanford University
Guerrilla Explorer’s Analysis
It should be noted that this reforestation theory is not a new one. And it’s not necessarily limited to the Americas either. For example, paleoclimatologist William Ruddiman has suggested in the past that the Black Death, which reduced Europe’s population from somewhere between 30-60%, reduced farming and thus, allowed for new tree growth.
In terms of evidence, Nevle and his team point to ice core samples from Antarctica. Samples corresponding to the Little Ice Age tend to have increasingly higher concentrations of carbon-13, which could be explained by the fact that tree leaves tend to absorb carbon-12. Also, the samples “suggest that levels of the greenhouse gas decreased by 6 to 10 parts per million between 1525 and the early 1600s.
“6 to 10 parts per million? Wow. That’s an extremely small change and, from what I understand, far too small to account for a significant geological event like the Little Ice Age. Plus, this data can be interpreted in other ways. For example, the oceans might’ve absorbed the carbon-dioxide, “perhaps in response to cooling induced by lower solar activity and increased aerosols due to volcanoes.”
To be fair, Nevle is on record stating that reforestation in the Americas was not the only factor that led to the Little Ice Age. But he does consider it a significant one. And the idea that changes in land-use might foster long-term climate change is an intriguing and potentially viable concept.
“…change and variability in land use by humans and the resulting alterations in surface features are major but poorly recognized drivers of long-term global climate patterns … these spatially heterogeneous land use effects may be at least as important in altering the weather as changes in climate patterns associated with greenhouse gases.” ~ Roger Pielke Sr.
Still, the fact remains that a carbon-dioxide reduction of just 6-10 parts per million is far too small to account for the resulting change in temperatures associated with the Little Ice Age. At the same time, there are plenty of other natural variables out there that seem far more likely, namely orbital cycles, reduced solar activity, increased volcanic or cometary fragment activity, inherent variability of climate, and/or a slowing of thermohaline circulation. It’s even possible that it was caused by natural forces we don’t yet understand.
Future evidence could change things. But for the moment, I think it’s safe to say that Christopher Columbus and the explorers that followed him were most likely not a major factor in bringing about the Little Ice Age.