The decade between 50 and 40 BC was one of the more remarkable decades in Mediterranean history. In 50 BC, the young Cleopatra, on the throne less than a year, issued a decree that required all grain ships to sail to Alexandria and to no other destination under pain of death. Less than two years later, the Nile river was at its lowest level ever recorded. Something was happening to the critical annual flood of the river, the lifeblood of the country and the force by which, in years of good flood, Egypt was the wealthiest grain bearing land in the world. In the same year (48 BC), two encounters would alter the political landscape forever. The Roman general Pompey, seeking refuge and a friendly welcome in Egypt after the disastrous Battle of Pharsalus, was murdered within sight of Alexandria. Soon after this drama, Caesar met Cleopatra in the Ptolemaic capital and formed an alliance with the last great monarch of antiquity. Cleopatra needed a Roman ally. The royal treasury was running as low as the Nile was flooding in these years. And then came the Ides of March in 44 BC - a political shocker to both Rome and to Egypt. Cleopatra, and her dream of reinvigorating the great Ptolemaic empire, turned to another Roman general, Marc Antony. But the dream would turn into a nightmare.
The eruption of Etna in 44 BC created a lot of portends in the Roman world, solar dimming, the sun “giving forth little heat,” and blood red moons but it did not change the world’s climate. Another volcano in a part of the world totally unknown to the ancients, however, was about to erupt, and it would spell disaster not only to Egypt and Rome but to many parts of the world. In one of the remotest places on Earth, the Aleutian islands in Alaska, in the winter of 43 BC, the largest eruption in the northern hemisphere in the last 2500 years produced a sudden and massive drop in global temperatures that persisted for a decade. Tree ring records from the White Mountains of California tells us that the decade between 43 and 33 BC was the second coldest in the northern hemisphere in human history, and it brought misery not only to Egypt, where the Nile failed to flood for several years in a row, but to Italy, which endured severe cold Summers that disrupted agriculture and military campaigns, and even to China. While we have to guess what the 30’s BC were like—little historical evidence survives from these years— recovery from famine and disease would not have been quick. By 31 BC, the Roman Empire had replaced both the Republic and the Ptolemaic kingdom.
The paper just published in PNAS that Frank Ludlow and I were involved in was led by Joe McConnell, a pioneer in the field of ice core Geochemistry at the Desert Research Institute in Reno (https://www.dri.edu/directory/joe-mcconnell/). He and his lab have produced many important papers in the last few years, including the ground-breaking paper led by Michael Sigl that revises the volcanic eruption sequence in Greenland and Antarctic ice cores. We knew thanks to Sigl et al. about an enormous eruption around 44 BC. Thanks to the new paper, we can revise slightly the eruption dating, from 44 to 43 BC. With tree rings we can understand and model the northern hemisphere cooling, a decade in length, forced by the eruption. Even more spectacularly, though, the volcano has been identified thanks to tephra analysis. It is not Etna or Apoyeque in Nicaragua, the two leading candidates, but Okmok, on the remote island of Umnak in the Aleutian islands of Alaska. This is now another example of a high north latitude eruption interfering with the East African Monsoon and with the Atlantic system of the Mediterranean as well.
All in all, this is a very exciting paper and illustrates a wonderful collaboration between scientists, historians and archaeologists. One thing is certain, the paper will generate all kinds of additional work, and our team is already at work on several follow-on papers on both regional and global climatic and historic impacts. We are certain others will jump in to respond as well. As the motto of my alma mater (The University of Chicago) says: crescat scientia, vita excolatur “Let knowledge grow from more to more; and so be human life enriched.”
Author: Joe Manning, PI (Yale University)