Following the assassination of military leader and statesman Gaius Julius Caesar on the Ides of March 44 B.C.E. during a meeting of the Senate, the struggle for power by the conspirators led to decades of civil war, marking the end of the Roman Republic. According to contemporary sources, the collapse of the Republic was accompanied by unusual weather phenomena, as the Sun mysteriously disappeared behind a mist and temperatures dropped significantly, causing widespread crop failures and famine, adding to the political crisis. Part of the described weather phenomena can be explained by ash clouds coming from Mount Etna on the island of Sicily. However, a study published in the journal Proceedings of the National Academy of Sciences argues that the dropping temperatures were the result of a far more remote volcanic eruption.
Ash layers discovered in ice cores from Greenland and Russia suggest that around 43 B.C.E. a powerful eruption ejected large amounts of volcanic ash and sulfur compounds, subsequently dispersed by atmospheric currents around the northern hemisphere. Analyzing the chemical composition of the recovered ash particles and comparing the composition with volcanic rocks of known origin, the researchers identified a possible volcanic source, Alaska’s Okmok volcano in the Aleutian Islands. Calculating the absorption of sunlight by ash particles and sulfur-aerosols and considering the size of the Okmok eruption, the biggest volcanic eruption in the last 2.500 years, the researchers estimate that the resulting volcanic mist could have cooled southern Europe and northern Africa by up to 7°C for over two years.
Unlike the Roman Republic, Gaius Octavius, a military leader who became the first emperor of the Roman Empire after Caesar’s death, may have benefited from the climatic tumult following a volcanic eruption.
A series of sulfur spikes, found in ice-cores recovered from the Arctic, suggests that at least two volcanic eruptions happened in 46 and 44 B.C.E. Weakening the Monsoon winds blowing from the Indian Ocean to Africa, the volcanic aerosols caused a series of dry years on the continent. Historic texts document a period of famine, diseases, and land abandonment, followed by a religious and political crisis in Egypt. Octavian’s troops easily overpowered the hungry and demoralized Egyptian soldiers.
In 30 B.C.E. the last pharaoh of ancient Egypt, the famous and beautiful Cleopatra, committed suicide after a series of disastrous defeats of the Egyptians by the Roman army, including the battle of Actium in September 31 B.C.E. when part of the fleet deserted. Soon after the once independent Egypt became a Roman province and Octavian used this military success to solidify his hold on the emerging Empire.