Did Halley's Comet Cause A Famine 1,500 Years Ago?

From Live Science:

A piece of the famous Halley's comet likely slammed into Earth in A.D. 536, blasting so much dust into the atmosphere that the planet cooled considerably, a new study suggests. This dramatic climate shift is linked to drought and famine around the world, which may have made humanity more susceptible to "Justinian's plague" in A.D. 541-542 — the first recorded emergence of the Black Death in Europe.

The new results come from an analysis of Greenland ice that was laid down between A.D. 533 and 540. The ice cores record large amounts of atmospheric dust during this seven-year period, not all of it originating on Earth.

According to the article, in 536-37, the Earth cooled by as much as 5.4 degrees F. (3 degrees C).

Ice core data record evidence of a volcanic eruption in 536, but it almost certainly wasn't big enough to change the climate so dramatically, Abbott said.

An extraterrestrial impact in the tropical ocean likely blasted these little low-latitude organisms all the way to chilly Greenland, researchers said. And Abbott believes the object responsible was once a piece of Halley's comet.
"There was, I think, a small volcanic effect," she said. "But I think the major thing is that something hit the ocean."

She and her colleagues have found circumstantial evidence of such an impact. The Greenland ice cores contain fossils of tiny tropical marine organisms — specifically, certain species of diatoms and silicoflagellates.