The climate was generally moderate in ancient Rome. There is evidence, however, that there were greenhouse gases present in ancient Rome, which contributed to a level of air pollution.
Ancient Rome is said to have existed between 753 B.C. and 509 A.D. The onset of the Roman Empire saw cooler climates since the glaciers in the Alps did not begin their retreat until around 300 B.C. There were a number of severe winters recorded in the early history of the empire but generally the temperatures across the period were mild.
Ancient Rome also saw wet seasons. Records show precipitations patters similar to those found in the Mediterranean today. Sea levels had dropped by comparison to modern levels by the first century A.D. As the Roman Empire was ending, sea levels began to rise and as such, a number of active ports during the time came to be underwater.
Scientists discovered that human activity during the Roman Empire led to a methane signature, which affected the entire planet. Methane is a byproduct of digestion and at the time, Romans were active agriculturists. Farms included various forms of domestic livestock, including cows, sheep and goats, all of which excrete methane gas. Wood burning from blacksmiths also produced methane gas. Between activities in the Roman and Chinese dynasties of the period, greenhouse gas and pollution were on the rise.