so how stable was agriculture in Greenland when colonised by the Vikings?
Agriculture's birthplace was in the middle east and sufficient to feed a relatively small population
The middle east's agriculture hasn't changed much - the population it has to feed has changed
the climate has not been stable for the last few millenia - the failure of agriculture due to climate has been one fo the main reasons for migratory trends in Europe
"During the Pre-Roman Iron Age (from the 4th to the 1st century BC), the climate in Denmark and southern Scandinavia became cooler and wetter, limiting agriculture and setting the stage for local groups to migrate southward into Germania"
