Climate of ancient Rome

The climate of ancient Rome varied throughout the existence of that civilization. In the first half of the 1st millennium BC, the climate of Italy was more humid and cool than now and the presently arid south saw more precipitation.^[1] The northern regions were situated in the temperate climate zone, while the rest of Italy was in the subtropics, having a warm and mild climate.^[1] During the annual melt of the mountain snow, even small rivers would overflow, swamping the terrain (Tuscany and the Pontine Marshes were deemed impassable in antiquity).^[1] The existence of Roman civilization (including the Eastern Roman Empire) spanned three climatological periods: Early Subatlantic (900 BC–175 AD), Mid-Subatlantic (175–750) and Late Subatlantic (since 750).^[2]

The written, archaeological and natural-scientific proxy evidence independently but consistently shows that during the period of the Roman Empire's maximum expansion and final crisis, the climate underwent changes.^[3] The Empire's greatest extent under Trajan coincided with the Roman climatic optimum.^[4] The climate change occurred at different rates, from apparent near stasis during the early Empire to rapid fluctuations during the late Empire.^[3] Still, there is some controversy in the notion of a generally moister period in the Eastern Mediterranean in c. 1 AD–600 AD due to conflicting publications.^[5]