Dagomar Degroot

History for an Uncertain Future

Welcome! I’m a professor of environmental history at Georgetown University in Washington, DC. I bridge the sciences and humanities to write histories that guide responses to today’s urgent challenges. I’m an expert on climate change, space exploration, and existential risk.

My newest book is Ripples on the Cosmic Ocean (Harvard University Press/Viking, 2025), which reveals how changes in cosmic environments influenced human history. I also wrote The Frigid Golden Age (Cambridge University Press, 2018), a book that, for the first time, explores how a society thrived in a period of preindustrial climate change.

I’m the lead editor of several volumes on the history of climate change, including the forthcoming Oxford Handbook of Resilience in the History of Climate Change. I publish equally in major scientific and historical journals, such as Nature and the American Historical Review, and write for popular audiences in, for example, the Washington Post, Aeon, and The Conversation.

I also create popular online resources, most recently the award-winning podcast, website, and video series, The Climate Chronicles. I’ve been interviewed by many news outlets, including the New York Times and CNN. I’ve shared the unique perspectives of the past with policymakers, corporate leaders, journalists, and the public in many cities, from Wuhan to Washington, DC.

I’m always happy to answer questions, to join new research efforts, and to consult on matters pertaining to my areas of expertise. Click here to send me a note.

Just Released: Ripples on the Cosmic Ocean

Our solar system is a dynamic arena where asteroids careen off course and solar winds hurl charged particles across billions of miles of space. Yet we seldom consider how these events, so immense in scale, influence our fragile blue planet: Earth.

In Ripples on the Cosmic Ocean, I trace the surprising threads linking human endeavor to the rest of the solar system. I reveal how variability in planetary environments shaped geopolitics, spurred scientific and cultural innovation, and encouraged new ideas about the emergence and fate of life. Martian dust storms altered the trajectory of the Cold War and inspired fantastical stories about alien civilizations. Comet impacts on Jupiter led to the first planetary defense strategy. And volcanic eruptions spewed sulfuric acid into Venus’s atmosphere, exposing the existential risks of climate change at home.

As we stand on the brink of a new era of space settlement, cosmic environments are becoming increasingly vulnerable to human activity. They may also hold the key to slowing the destruction of environments on Earth. Ripples on the Cosmic Ocean urges us to develop an interplanetary environmentalism across a vast mosaic of entangled worlds and to consider the profound connections that bind us to the cosmos and each other.

You can now watch a series of videos introducing the ideas, sources, methods, and goals of Ripples on the Cosmic Ocean.