Absolutely. You may have heard about the "Year Without A Summer" -- a term applied to 1816 when temperatures plummeted in Europe owing to the eruption of Mount Tambora and leading to a large loss in agricultural yields. Tambora was the largest eruption since late 535 / early 536 when Krakatoa blew its top.
As in 1816, this led to a year where crop yields and temperatures decreased. Procopius, an Eastern Roman Historian, wrote:
the sun gave forth its light without brightness, and it seemed exceedingly like the sun in eclipse, for the beams it shed were not clear.
The Irish 'Annals of the Four Masters' notes a failure of bread in 536-539, and Cassiodorus, a Western Roman Senator at the time, wrote in part:
We marvel to see no shadows of our bodies at noon, to feel the mighty vigour of the sun's heat wasted into feebleness, and the phenomena which accompany an eclipse prolonged through almost an entire year.
It was by no means limited to Europe either. It's estimated that up to 70% of the population in parts of China died from famine during this time, and there may have another large eruption in 539-540 to add to the misery.
Some sources:
Smithsonian Magazine: Sixth-Century Misery Tied to Not One, But Two, Volcanic Eruptions
Are you talking about the rising sea-levels/increased salinity that paved the way for more barley/millet harvests as opposed to wheat along the north west of France through to what is now modern day Denmark?