The global warming of the last century needs to be placed in a broader temporal context in order to determine its singularity and distinguish the underlying causes, both natural and anthropogenic. Climate variations over the last few millennia can be used to test multiple hypotheses, with records that are generally sufficiently reliable.
For these remote periods, connections between human populations were relatively limited compared with our globalized society. It is therefore a priori easier to identify the impact of regional climatic changes on ancient societies. These lessons from history and prehistory can also inform our choices and reactions to current climate change and its regional expressions, which are often amplified compared to global trends.