What do we know about the climate events that happened around 535/6 CE? I've read suggestions of volcanic eruptions or comets impacting the earth, and claims that these events resulted in several years of terrible famine which may have accelerated the social restructuring that followed in the latter half of the sixth century (in Europe, at least).
What is the current consensus about these ideas? Was there a serious climatic event? What caused it? Do we think climate played a role in later 6th century society?
It's weird that I don't know the answers to this - it seems to never come up in Anglo-Saxon archaeology, which makes me question whether the idea itself is bogus, or whether Anglo-Saxon archaeology is still too mired in culture history (or radical postprocessualism) to ask these kinds of questions.
Climate change was not just limited to Europe at the time. A recent study of caves in Guerrero and the Quelccaya icecap in Peru reaffirm the hypothesis that drying spells occured in the 600s in Mexico and Peru which played a role in the downfall of polities in each respective region. Previous work had put forth the idea that drought triggered migrations in north-central Mexico which may have further disrupted polities like Teotihuacan and lead to the formation of new polities like the Toltec state. Perhaps knowing the date for climate change in Europe is more fine grained with written records or perhaps change struck Europe earlier than Mexico and Peru. It is safe to say that something was going on around the world around the same time.
I don't think there's a consensus yet unfortunately. I did some reading on this a while ago (see here) and I thought that historians didn't think it was too important, since although the cloud was mentioned in many primary sources, all of them were far more concerned with the plague that followed shortly afterwards.
Three articles were particularly useful for me back then, though I noted that archaeologists/scientists wrote about this in more apocalyptic terms than the perspective taken by historians (see Arjana's paper for the argument that it wasn't that big a deal):
Arjava, A., The Mystery Cloud of 536 CE in the Mediterranean Sources, Dumbarton Oaks Papers (2005)
Graslund, B. & Price, N., Twilight of the gods? The ‘dust veil event’ of AD 536 in critical perspective, Antiquity (2012)
Löwenborg, D., An Iron Age Shock Doctrine – Did the AD 536-7 event trigger large-scale social changes in the Mälaren valley area?, Journal of Archaeology and Ancient History (2012)
There's also a fun article linking the cloud to Gildas, which I thought was quite amusing. I think McCormick is doing some work on environmental history now, so it's probably useful to see if he's published anything on this lately - I only recently found out that he compiled a spreadsheet of all natural disasters in the Roman/post-Roman world (see here), which might be useful for you as well for a broader perspective. His article here also spent a few paragraphs specifically in 536, which also came with a helpful bibliography on this topic:
The 536 event has a bibliography all its own: Joel D. Gunn (ed.), The Years without Summer: Tracing a.d. 536 and Its Aftermath (New York, 2000); Antti Arjava, “The Mystery Cloud of 536 CE in the Mediterranean Sources,” Dumbarton Oaks Papers, LIX (2005), 73–93. L. B. Larsen et al., “New Ice Core Evidence for a Volcanic Cause of the a.d. 536 Dust Veil,” Geophysical Research Letters, XXXV (2008), L04708.
Let me know if your research turn up something as well. It's something that I'd love to read more about since it fits quite well into my 'EVERYTHING IS CONNECTED' argument about late antiquity.
A long while ago I read a book by David Keys called "Catastrophe" about this series of events, and at the time I wrote it off as trashy PopHist of the sort where the author posits a thesis at the beginning of the book and then spends the rest of the book assuming that the thesis is true and using it as a jumping off point for explaining other events (instead of trying to use various events and documents to prove the thesis). Recently though I read a much more scholarly book "Plague and the End of Antiquity" (can't recall the editor, sorry) that deals with the 5-6th centuries and examines textual and archaeological evidence for bubonic plague throughout the Mediterranean and Atlantic worlds. Climate events are mentioned though it's not the focus of the book; but many of the articles cited the Keys work in respect of climate events in the period. I've dug it back out of storage and I'm going to give it another read to see if I was wrong in my initial impression. It's a bit older now (late 90s I think) but you might find it to be a good jumping off point. The plague book is much more recent (2014?) and its repeated reference to Keys suggests there isn't really any newer scholarship in the field. (If anyone in this thread knows of more recent work, I'd love to hear about it!)