The PDF [probability density function] peak between 1430 and 1455 AD corresponds with a large eruption in 1452 AD, although the ages of the three largest 5-year bins appear to precede the eruption date.Wow. If you were arguing that the increasing cold caused volcanic eruptions, then the sequence here makes sense. It would be a stretch to argue this; maybe even require some magic, but at least the order would be right. The climate became colder; a big volcanic eruption happens near the end of this increase in cold. But the paper is arguing the opposite: that big volcanic eruptions cause the cold. So how does a "large eruption in 1452 AD" explain the cold that happens almost entirely before 1452? Does the climate know what's coming, and make adjustments?
Maybe the rest of the paper makes sense, but sentences like this make me think that they are engaged in a faith-based activity, not science.