Mixed greens

The message of Janus

Posted 1/12/22

January takes its name from Janus, the deity ancient Romans believed presided over beginnings and endings; births and journeys; gateways, doors, bridges, borders and other points of transition; trade …

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Mixed greens

The message of Janus


January takes its name from Janus, the deity ancient Romans believed presided over beginnings and endings; births and journeys; gateways, doors, bridges, borders and other points of transition; trade and commerce; conflict and reconciliation; and time itself. Depicted with two faces, he looked simultaneously to the past and to the future. The Romans celebrated this duality just after the winter solstice and placed him at the beginning of the modern calendar, inspiring our New Year custom of reflecting on the year that has passed and looking ahead with fresh hope, wishing each other good fortune and resolving to change for the better.

Over the holiday I had the chance to catch up with new research in the field of paleoclimatology—the study of earth’s climate over hundreds of thousands of years. Paleoclimatologists study tree rings and core samples from lakes, bogs, ocean beds and coral reefs to gather evidence about the climate, but the most dramatic information comes from ice core samples collected from glaciers and ice sheets around the world. These samples can go more than a mile deep, providing data dating back 800,000 years. According to NASA, ice cores preserve all kinds of atmospheric evidence in the form of particles—dust, pollen, ash, trace minerals, sea salt—and bubbles of air that capture greenhouse gases like carbon dioxide and methane, trapped over millennia in identifiable layers of compacted ice. Through this evidence, scientists have refined their climate models and identified the severity and extent of events like major volcanic eruptions, going back thousands of years.

What’s relatively new in the field of paleoclimatology is that, as the quality of data analysis has grown along with the sheer volume of information from all of these various climate proxies, scientists can now pinpoint occurrences of cataclysmic events like volcanic eruptions with far greater accuracy. In turn, this greater certainty has given historians a new understanding of the extent to which major volcanic eruptions and the prolonged disruptions in global temperature that follow can be correlated with agricultural collapse, famine, warfare, pandemics, political upheavals and periods of intense social unrest in the historical record.

For example, a new study published in Springer Nature’s online journal, “Communications Earth & Environment,” used state-of-the-art ice core data to model volcanic eruptions over 2,000 years of Chinese history, and found what the paper describes as “a systematic association” between volcanic eruptions and the collapse of 62 out of 68 ruling dynasties. The authors defined collapse as episodes characterized by “rapid reductions in socioeconomic complexity, population loss or displacement, and/or political discontinuity.”

The climate impacts of volcanic eruptions typically started with disruption of agriculture and the food supply, with short-term catastrophic impacts including multiple years of unusual summer cooling, crop failure, drought and famine.

Links to sources


Gao, C., Ludlow, F., Matthews, J.A. et al. Volcanic climate impacts can act as ultimate and proximate causes of Chinese dynastic collapse. Commun Earth Environ 2, 234 (2021). https://doi.org/10.1038/s43247-021-00284-7



The authors note the importance of other stressors, including epidemics, mass migrations and demographic changes, warfare, poor leadership and government corruption or inefficacy, and environmental degradation. To varying degrees, these stressors might pre-exist or be exacerbated by the environmental impacts of a major volcanic eruption, and the authors note the potential for interaction and compounding of these stressors as a result of the climatic event. Another important part of the discussion centers on the historical importance of traditional Chinese belief systems, which interpreted natural disasters as signs that a ruling dynasty had lost the “mandate of heaven”—the divine right to rule.

This look backwards left me pondering the present, since there is ample evidence that climate science interacts with our own pre-existing societal stresses and belief systems. Our concept of Western history has for so long been dominated by the idea that larger-than-life political figures, mostly “great men,” shape the world through sheer force of will and their outsized personalities. Other perspectives emphasize technological advancement, with Nature as a neutral backdrop to be acted upon by human ingenuity. Could our current, painful age of anxiety arise from the disruption of these illusions, just as the dread of nuclear annihilation hovered over the second half of the 20th century?

In 2021, more than 40 percent of Americans experienced a climate-related disaster, according to a recent analysis by the Washington Post, and the Oxford English Dictionary officially added “eco-anxiety” to the lexicon. The realization that we do not control the forces of nature may lock us in self-perpetuating feedback loops of fear and exploitation, or show us, Janus-like, the way to new beginnings.

Janus, January, paleoclimatology, climate change, climate science, eco-anxiety


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