It may have actually been the opposite, the medieval warm period overlaps quite well with the Viking age meaning it’s entirely possible that the longer growing period caused a population surplus and overflow. I actually have a hypothesis that the same thing happened in antiquity causing the Germanic migration out of Scandinavia. Same thing possibly caused the Nordic Bronze age.
It may have actually been the opposite, the medieval warm period overlaps quite well with the Viking age meaning it’s entirely possible that the longer growing period caused a population surplus and overflow. I actually have a hypothesis that the same thing happened in antiquity causing the Germanic migration out of Scandinavia. Same thing possibly caused the Nordic Bronze age.