“We are at a crossroads in human history. Never before has there been a moment so simultaneously perilous and promising.”
So reads an epigraph in my new book Our Fragile Moment, which is about the lessons we can learn from the past about the climate crisis we face today. The quote itself is from the great Carl Sagan, from his 1979 book, Broca’s Brain.
Sagan was a seer—not in the mystical sense (pseudoscience and magical reasoning were among Sagan’s greatest peeves), but in the historical sense. He displayed the foresight that comes from a deep understanding of our world. In words written nearly half a century ago, Sagan seemed to be describing the very fragility of the moment we find ourselves in today, where the promise of technology—think generative AI and CRISPR—contrasts with the perils of our technology, and the damage to our global environment that it has caused.
Sagan’s words and thoughts infuse Our Fragile Moment. Indeed, it was Sagan who first inspired my aspiration to pursue a career in science back in the early 1980s as I grew up watching his PBS series, Cosmos. It exposed me and others of my generation to the wonders and grandeur of science and the mysteries of our Universe that science could help solve. Sagan’s legacy would prove prophetic for me in ways I couldn’t possibly have imagined back then, however.
Sagan played a pivotal role in raising awareness of the threat of nuclear war in the mid 1980s at the height of cold war tensions between the United States and Russia and an escalating arms race. His scientific work showed that the massive detonation of nuclear warheads would not just cause physical destruction, or fatalities from exposure to radiation, but far more widespread mortality and suffering due to the abrupt planetary cooling that would result, wiping out crops and creating mass upheaval.
Such a “nuclear winter” was analogous to what scientists had only recently discovered to have caused the extinction of the (non-avian) dinosaurs 66 million years ago. A massive asteroid collision ejected dust and particulate matter into the atmosphere, blocking out the sun and chilling the planet for years. That deep freeze killed off all large fauna that couldn’t burrow into the ground to escape the cold (for a more through discussion of this connection, see my recent commentary in the Bulletin of the Atomic Scientists).
Sagan publicized his findings far and wide prior to publication, calling a major press conference and publishing an article in the widely read “Parade” insert of Sunday newspapers across the USA. While it is unconventional for scientists to promote their findings before they’ve gone through the peer-review process, Sagan felt that the existential threat of nuclear winter called for such extraordinary measures.
His policy advocacy incurred the wrath of cold warriors and members of the military-industrial complex, who promoted and indeed profited from the continued escalation of the arms race. They set their sights on Sagan. A group of conservative cold-war physicists, with support from industry special interests, formed an entity calling itself the “George Marshall Institute” (an excellent historical account can be found in Oreskes and Conway’s Merchants of Doubt). Its main purpose was to provide a vehicle for launching attacks against Sagan, not just criticizing his scientific work, but questioning his objectivity and integrity. Sagan was not deterred by the attacks. Possibly, he was emboldened by them. I say that, because that’s how I reacted when I would come under similar attacks 15 years later.
In the late 1990s, my co-authors and I published the “Hockey Stick” curve, which laid bare the dramatic warming coinciding with the industrial era, underscoring the threat of ongoing fossil fuel burning. It—and I—would be attacked by climate-change deniers, and some of the same industry special interests that sought to discredit Carl Sagan for his nuclear winter messaging. Now heavily funded by the fossil-fuel industry, the George Marshall Institute was one of the groups that attacked me and the Hockey Stick.
Yet, following Sagan’s lead, I did not allow myself to be deterred. Playing a central role in the contentious debate over human-caused climate change was hardly what I had in mind when I’d left pure physics research in the early 1990s to work on the more wide-open problem of climate modeling. However, I felt I had an obligation to defend my science—and the science of climate change more generally—from what I considered to be bad faith, agenda-driven attacks. In so doing, I’ve come to embrace the opportunity—indeed, the privilege—I have been given to inform the public discourse over climate change.
Decades later, as the evidence of an unfolding climate crisis has become indisputable and plain for all to see, polluters and those doing their bidding have turned to other tactics to keep us reliant on fossil fuels. Denial has given way to deflection, distraction, division, and last, but not least of the “d” words, delay. Chief among delay tactics is the promise of future technology that will magically solve the problem, even as we continue to burn fossil fuels, so-called geoengineering.
In the course of my own communications efforts, I often first ask myself ,“What would Carl think?” In the case of geoengineering, I’ve come as close as possible to getting a direct answer. In his book, Earth in Human Hands, astrophysicist David Grinspoon—who was the son of Sagan’s best friend and Harvard colleague Lester Grinspoon, and so close to Sagan he called him “Uncle Carl” when he was a boy—channels Sagan on this topic, providing us a glimpse of what he very well might have thought and said:
“I believe that were he here today, Carl would urge extreme caution about geoengineering. I can close my eyes and hear his deep, resonant voice saying “It would be an act of consummate recklessness and arrogance to try to jury-rig the only home we have, to attempt a quick-and-dirty repair job on the complex, deeply mysterious, and exquisitely balanced mechanisms that all human life, and all other life we know of, depends upon, when we are still so ignorant about their functioning”.
As I read this and my mind’s ear intones Sagan’s uniquely sonorous voice, and I draw upon what I know of him from his writings and outreach efforts, this rings true to me.
This matter isn’t one of just academic or scientific interest. In a recent article that garnered substantial media attention, another high-profile scientist, Dr James Hansen—sometimes called the “Grandfather of Global Warming”—argued that global warming is exceeding model predictions, and we have no choice but to turn to geoengineering. Hansen and colleagues advocate a specific form of geoengineering euphemistically called “Solar Radiation Management”, in which particulates such as sulphates are injected into the upper atmosphere in an attempt to block out incoming sunlight. Critics—including myself—have pointed out that such interventions could both (a) result in disastrous unintended consequences and (b) provide an excuse for polluters to continue with business as usual, delaying critical efforts to address the climate crisis in the only safe and reliable manner (decarbonizing our societal infrastructure).
And so we return to the Sagan quote with which we began. For we truly find ourselves at a “fragile moment” in history where technology offers us both promise—in the form of the clean, safe and renewable energy sources with which we can power our civilization—and desperate and dangerous gambits like geoengineering. It’s fairly clear to me what path Carl Sagan would have advocated.
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Michael E. Mann is presidential distinguished professor and director of the Center for Science, Sustainability and the Media at The University of Pennsylvania. He is author of the new book “Our Fragile Moment: How Lessons from Earth’s Past Can Help Us Survive the Climate Crisis.”
Image: Tony Korody