Climates and human societies for the past two thousand years

Current global warming must be placed in a broader temporal context in order to determine its singularity and distinguish the underlying causes, both natural and anthropogenic. Climatic variations never repeat themselves identically, but the same mechanisms are at work and are the subject of numerical simulations using the same models used to forecast possible futures. Studying the climate of the historical period is therefore crucial to testing our understanding of the climate system. For most of the last two millennia, connections between human populations were limited by comparison with our current globalized society. This is an advantage for identifying the impact of regional climate change on populations. By considering human reactions (or lack of them), the study of climate in the historical period can also inform our choices in the face of current warming and its amplified regional expressions compared to the global trend.