At the end of every year, we tend to grumble about how terrible it was. Political upheavals, mass shootings, global warfare and environmental disasters all make us think that whatever year we just (barely) got through had to have been the worst.

But historians would like to remind us that we have it pretty good, at least compared to those poor saps who had to live through A.D. 536 — the year they declared the worst in human history.

What made A.D. 536 just so awful? For starters, we lost the sun.

There goes the sun

Sometime early in 536, a thick haze covered Europe, the Middle East and some of Asia. The sun was visible, but that good, life-giving warmth wasn't breaking through the fog. "For the sun gave forth its light without brightness, like the moon, during the whole year," Byzantine historian Procopius observed. Other reports from this hazy time include a summertime snowfall in China, and Europe experienced "spring without mildness, summer without heat."

The haze lasted for 18 months.

The mysterious gloom resulted in a steep temperature drop, somewhere between 34.7 degrees Fahrenheit (1.5 degrees Celsius) to 36.5 degrees. This decline in temperatures kicked off the coldest decade in 2,300 years. The wonky weather resulted in crops not growing and severe food shortages. Irish Annals reported three years of no bread between 536 and 539.

By A.D. 541, things significantly worsened due to a bubonic plague outbreak. The pandemic ravaged the eastern Byzantine Empire, claiming between a third to half of the empire's population, hastening its collapse.

"[A.D. 536] was the beginning of one of the worst periods to be alive, if not the worst year," medieval historian Michael McCormick from the Harvard University Initiative for the Science of the Human Past told Science magazine.

Always with the volcanoes

A volcano erupts in Iceland The eruption of a volcano in Iceland may have been responsible for plunging the Northern Hemisphere into a hazy darkness in A.D. 536. (Photo: Nathan Mortimer/Shutterstock)

We've known about the 536 dust veil for years. Tree ring chronologies conducted in the early 1990s told of a massive cooling event in either late 535 or early 536, with another drop recorded in 542, indicating a potential double-whammy of cold temperatures and bad air sometime in the early 540s.

A team of researchers that included McCormick suggests that the eruption of an Icelandic volcano was responsible for the worst year in human history.

The researchers analyzed a 235-foot (72-meter) ice core sample pulled from a Swiss glacier, studying dust and other airborne particles trapped in the core. They learned about a Saharan dust storm and an earlier-than-originally-thought silver mining boom. But in the case of 536, the team found shards of volcanic glass which they traced back to volcanic rocks in Iceland. These shards, the researchers contend, are proof of a massive volcanic eruption that loosed a massive plume of ash, which shrouded the Northern Hemisphere for more than a year.

The researchers published their findings in the journal Antiquity.

Another suspect

This doesn't settle the debate, however. A 2015 study published in the journal Nature agrees that a volcano caused the dust veil, but pinpoints a volcano in North America — not Iceland — as the culprit. Another eruption in 539 or 540 is also linked to North America, potentially explaining the temperature drop recorded in the tree rings.

"Iceland is a lot closer to Britain and North West Europe than California, which means that the impact of this eruption at the time on climate in these areas would have been much greater than previously thought," Christopher Loveluck from the Department of Classics and Archaeology at the University of Nottingham in the U.K. and lead author of the Antiquity study said in a statement.

"It would have made places very cold very quickly and would have been most felt in Britain and places in North Western Europe. The consequences for these areas would have been immediate, with an increased likelihood of famine and ill health due to poor crop yields."

The previously mentioned silver mining boom was noted in the core by 640, likely the result of silver mining operations. This, the researchers of the Antiquity study contend, indicates that a recovery was underway by then, with the emergence of a new merchant class leading Europe out of a desolate period.

So maybe instead of complaining about how horrible everything is, remember this history lesson — and be thankful you weren't around in 536.

At least this year wasn't as bad as A.D. 536 — the worst year in human history
In A.D. 536, a volcanic eruption sent a thick haze into the air that blocked the sun over Europe, the Middle East and some of Asia for 18 months.