Did Past Climate Change Cause Medieval Black Death?

Recent research suggests volcanic eruptions in the tropics
around the year 1345 was the spark that eventually 
led to the Black Death in Europe.  It was an 
instance showing that climate change, whether
natural or man made can have 
tragic, unintended effects.

Climate change deniers have one argument that is at least partly right: Climate change has always happened. 

There's the human-induced climate change we're experiencing now. Fossil fuel emissions keep making the planet hotter and hotter.  

As most of us know, many other things can change the climate, sometimes slowly, sometimes at the drop of a hat. Like volcanic eruptions. 

Maybe the most famous instance was in 1815, when the erupting Mount Tambora in present-day Indonesia threw so much gunk into the atmosphere that it created the "Year Without a Summer" in 1816.

Crop failures and other calamities with that cold summer causes suffering world wide. 

There's evidence another volcano caused an even more extreme human disaster - the Black Death in the 14th century.  . 

It was easily among the worst pandemics in human history. It killed probably half of Europe's population. 

So what set it off? Recent research seems to indicate a volcano or volcanoes started the dominoes to topple.  

Researchers digging through historical documents, tree rings, ice core samples from Antarctica and Greenland came up with an explanation for the Black Death. The research was recently published in the journal Communications Earth and Environment. 

According to CNN:

"The study authors believe an eruption occurred around 1345, about two years before the start of the pandemic, from either a single volcano or a cluster of volcanoes of unknown locations, likely in the tropics. The resulting haze from volcanic ash would have partially blocked sunlight across the Mediterranean region over multiple years, causing temperatures to drop and crops to fail." 

The resulting grain shortage threatened to spark civil unrest or even a famine. Italian city-states like Venice and Genoa, resorted to emergency imports from near the Black Sea, and that helped prevent trouble.

At first.

But then there's this, according to CNN:

"However, ships that carried the grain were loaded with a deadly bacterium: Yersinia pestis. The pathogen, originating from wild rodent populations in Central Asia, went on to cause the plague that devastated Europe."

The bacteria can survive for months on grain dust, so it had no trouble making it to Venice and Genoa and places like that. It survived in grain storage, and when the grain was traded elsewhere in Europe. 

The bacterium that was in the grain infects rat fleas, which in turn hits rats and other rodents. The bacterium pretty much killed all the rats once they got to Europe. So, the bacteria had to find some other mammal to attack. Those mammals were human Europeans. 

The bacterium was really effective. Before the Black Death, the world's population was a little under 450 million. Between 1347 and 1351, the Black Death killed more than 25 million people. 

The bottom line: Climate change, in this instance natural, temporary and brief, helped trigger one of the most disruptive and tragic chapters in human history. 

Just to be clear, I'm not at all suggesting climate change had anything to do with the Covid pandemic that started in late 2019 and engulfed the world in 2020. That pandemic and climate change are two completely separate issues.

However, the Black Death study is a reminder that the climate change we're going through now can have scary effects that could take us all by surprise. This blog has for years been telling you about things climate change has caused, and things it might cause. 

But there are other effects of climate change we have no way of predicting. As they say, we don't know what we don't know.