Gather round the fire, oh traveler, and listen to an ancient story. The days of the old gods are numbered; one day, catastrophe will strike and the final battle-to-end all battles will take place. Here the gods will die and the world as we know it will end. This is the story of Ragnarök, the apocalyptic narrative at the heart of Norse mythology, which has become well-known through recent movies and game franchises. However, scholars have started to wonder whether this mythical event may have actually happened.

Before Ragnarök arrives, so the story goes, the world will be beset by “Fimbulwinter” (the Great Winter), a three-year-long disastrous winter that sees no intervening summer. During Fimbulwinter, snow blows in from all directions, temperatures plummet, and famine and suffering spreads across the land. Wars spring up among humans as they struggle to survive in these extreme conditions, and soon after Ragnarök is destined to begin.

This event has often been interpreted as a symbolic narrative device that highlights the rise and fall of human civilization, the power of nature, and the Norse cycle of destruction and rebirth. However, some scholars have wondered whether Fimbulwinter may have had a real-world equivalent.

The year 536 CE has been recognized as potentially the worst year in human history, as one or possibly multiple volcanoes erupted in the Northern Hemisphere. This event triggered a decade-long “volcanic winter” that covered the globe in a veil of ash and sulfur gases that blocked the sun. The devastation affected the lives of people across the world – China witnessed snows in summer and the average temperature in Europe fell by 2.5°C (4.5°F). Across the Atlantic, Peru witnessed droughts, while bubonic plague eventually made its way to Egypt in 541.

According to new research from the National Museum of Denmark, this volcanic winter may have really been interpreted as a sign of the end times and could be the root of Fimbulwinter.

“Many have speculated about it, but for the first time we can now demonstrate that perhaps the greatest climate disaster in human history affected Denmark – catastrophically,” Morten Fischer Mortensen, a senior researcher at the museum, said in a translated statement.

Until recently, it was not clear to what extent this climatic event affected Denmark, but the new study into farming practices in the country from the Bronze Age to the Viking Age has shown how severely it was impacted. They achieved this by examining the annual rings in over 100 pieces of oak from the sixth century, which indicate poor to no growth over this time – especially during the summers between 539 and 541.  

“When the trees could not grow, there was also nothing that could grow in the fields. In a society where everyone lives off agriculture, this has disastrous consequences. This is supported by other studies we are undertaking. Here we see a drastic decline in grain production, we see areas that are simply abandoned by people, and forests that spread beyond the abandoned fields,” Mortensen added.

“In Norway and Sweden, researchers believe that up to half the population died, and it is not inconceivable that the same happened in Denmark. It almost gives me chills to see these small, narrow annual rings, because I know how much sorrow, death and misfortune they represent.”

Interestingly, archaeological evidence also supports the idea that this was a harsh time in Denmark, as several large gold finds – gold horns, the Vindelev Hoard, and the Broholm Hoard – appear from this period, but treasures created from earlier periods appear surprisingly little after this. The current interpretation is that everything of value had already been sacrificed to the gods in the hope it would return the Sun.

At the same time, analysis of the crops grown in the following years suggests the survivors of the harsh winters were forced to diversify their options for better food security. It seems the cultivation of rye was one such development as it became increasingly common in the following centuries, possibly because it is less Sun-demanding than other cereals. Rye effectively became an insurance against future hardship.

“One can speculate whether the rye bread originates from this period, because historically rye has been used for bread. It’s an interesting thought if our love for rye bread is born out of a climate crisis,” said Mortensen.

Of course, this is not definitive proof that the mythological Fimbulwinter was based on these events, but the coincidence is certainly compelling.

“Such myths may well be free imagination, but they may also contain an echo of truth from a distant past. Several people have speculated whether the Fimbulwinter refers back to the climate disaster in the sixth century, and now we can state that there is a great match with what we can demonstrate scientifically,” Mortensen concluded.

The study is published in the Journal of Archaeological Science: Reports.