Planetary Crises: The End of “Our Fragile Moment” on Earth?

With climate change and extreme weather events making daily headlines, Michael Mann’s new book Our Fragile Moment: How Lessons From Earth’s Past Can Help Us Survive the Climate Crisis provides an in-depth look at our planet’s critical events triggered by nature at work alone—illustrating what we can learn from them while battling our own, human-made, crisis.

Working in climate change, I often hear the claim that the Earth has been through, and survived, several crises in the past, and the climate crisis will be no different than these earlier events. While climate change is nonetheless painted in stark detail in this book, Mann provides a user-friendly guide to what kind of events have preceded this current crisis, and how various species did (or did not) survive these past junctures. Most importantly, he finds parallels (and also differences) between these past events from characteristics of the climate crisis. The outcome is both reassuring in some aspects, and frightening in others.

Mann is a renowned climate scientist, and director of the Center for Science, Sustainability & the Media at the University of Pennsylvania. One of his most famous works is the “hockey stick” graph (first published in 1990s), which became an icon of climate science. It indeed looks like a hockey stick lying on its side, blade tilted up. Global average temperature is on the Y-axis, time along the X-axis. The graph shows thousands of years of a relative stable climate flat as time progresses along the X-axis—but the blade sticks up at the far right when temperature increases rapidly due to human-induced changes to the climate since the beginning of the Industrial Revolution.

As Mann himself describes the graph in his book, the sheer simplicity of the sharply angled line made it so popular: “You do not need to know about the complexities of climate science to understand the message of the graph: that we are perturbing our planet’s climate in a profound way.”

The graph also made Mann the target of significant attacks from climate deniers. As a result, Mann sued two climate deniers for defamation, and over a decade after initiating the litigation, in February he was awarded $1 million in damages by a jury. His work, and public persona defending climate science, has made him a profound and important thinker in the climate change arena. Most relevant for this piece, his new publication makes complex Earth history accessible to non-scientists.

Mann’s book is clearly written and easily accessible. It charts major events in Earth’s history, and connects each to the climate crisis. He also helpfully weaves in his own personal narrative and experiences with some of the effects of the climate crisis that we see today.

The result is some tamping down on climate doomism—while the climate crisis has some hallmarks of these other catastrophic events, it does not include all of them. As a result, he helpfully navigates the reader toward an understanding that the climate crisis is real, requires urgent attention, and may cost hundreds of millions of lives if more urgent political action is not taken. But he is also careful not to fall into the mire of the inevitable destruction of human civilization from climate change. Instead, he links what the climate crisis might look like with each degree or fraction of a degree of warming.

He is also very careful in this work to clarify the narrative around uncertainty. Many climate sceptics and climate deniers point to uncertainty in climate models to build a tale that we do not need to act urgently on climate change. Mann takes the opposite view. In many parts of the book he illustrates that uncertainty is not our friend. Some climate models are not able to, or not accurately able to, account for certain phenomena, and so may be overly conservative and thereby can underpredict key impacts.

An example he gives toward the end of the book is the melting of the Greenland ice sheet, which appears to be exceeding past model predictions. The additional water entering the oceans would not only raise sea levels, but may contribute to the collapse of the Atlantic Meridional Overturning Circulation—and this could already be underway. These underpredicted events could interact with other climate-related events, and cause more cascading negative effects than currently anticipated. In this respect, Mann is clear that uncertainty is cause for more (not less) urgent action on reducing emissions of fossil fuels and other measures.

Mann begins his work by explaining how fragile the climate conditions are that allow humans to live on Earth. He explains that there is a relatively narrow envelope of climate variability within which human civilization remains viable. The concentration of carbon dioxide in the atmosphere today is already well outside the range that existed when our civilization arose. This is our fragile moment. Despite this, there is also, within Earth’s history, lessons around climate resiliency (he explains this through the Gaia effect). As a result, while climate change is a crisis, it is, for now, a solvable crisis. While we have the advantage of anticipating the future through climate models, he cautions that we also have to respect planetary thresholds—exceeding those thresholds will exceed the adaptive capacity of human civilization, so past examples of societal collapse are important warnings for us to heed.

Mann walks us through the Permian-Triassic extinction (or the Great Dying) 250 million years ago. Ninety six percent of marine species died off, along with two thirds of amphibian and reptile species, and one third of insects. What caused this event? Spiking levels of carbon dioxide caused massive heat and drying, and dramatic falls in oxygen, leading to hypoxia, all probably caused by volcanic eruptions. These events were all concentrated on the one continent on the globe at the time, which geologists call Pangea.

Our input of carbon dioxide is actually more rapid than that which occurred during the Great Dying; indeed, it is almost a hundred times faster, which is not good news, particularly for our marine environments. Recent research demonstrates that the oceans are warming faster than models originally predicted. Again, as Mann reiterates throughout his work, uncertainty is not our friend.

While today we have similar effects of atmospheric carbon dioxide increases and ocean acidification going on, we do not seem to have other similar contributors to the Great Dying, such as atmospheric anoxia (lack of oxygen) or the global hydrogen sulfide “stink bomb” effect (think rotten eggs) so while there is cause for concern, we are not automatically doomed to replicate the Great Dying.

Mann also draws comparisons, and distinctions, with the K-Pg event—the asteroid collision in what is today Mexico’s Yucatan region which led to the extinction of the dinosaurs. This massive event created significant cooling, not heating. But it is the rapid scale of the change which should give us pause. Plants and animals cannot adapt to rapid changes, and the rate of change today of shifts in climate zones exceeds the ability of species to adapt and move to more favorable regions.

Similar lessons can be learned from the Paleocene-Eocene Thermal Maximum (otherwise known as Hothouse Earth). This period of rapid warming occurred 55 million years ago. Rapid releases of carbon that accompanied this event are probably the closest analogy we have to the existing climate crisis. And tellingly, the elevated levels of warmth lasted for 200,000 years after the Hothouse Earth event was triggered.

While our rate of warming is faster, Hothouse Earth did not see a “methane bomb” such as the one that concerns us today with permafrost melting (although he caveats this, as our methane locations differ), and Hothouse Earth was characterized by greater climate sensitivity. This means there is good news and bad news. The good news is if we maintain the climate policies we have today, we are unlikely to experience the same Hothouse Earth dystopia. The bad news? If we do not ambitiously increase our climate action and instead reach the upper end of temperature predictions (7°F by the end of the century), Mann directly states that we and our progeny are in for a world of hurt.

Mann ends with a balanced call to action. Instead of submitting to doomsayers and the emotions of fear, anxiety, and depression, which can lead to passivity, he charts a call to action through the use of righteous anger. The failure of ambitious climate action is not a failure of technology, science, or even society. It is a failure of politics—funded and underpinned by climate deception tactics of the fossil fuel industry. The identification of these bad actors can motivate us to engage in political action to combat these forces.

He ends with a measured and sober picture of the future. Even in a business-as-usual scenario, where we do not exceed 3°C by the end of this century, there will be no methane bombs, no runaway warming, and no Hothouse Earth. But there will be a tremendous amount of human suffering, species extinction, loss of life, chaos, conflict, and destabilization of social structures.

This would be the end of our fragile moment—and is not a world any of us should want to live in. According to Mann, if we seize this brittle juncture to rapidly phase out fossil fuels and take other urgent and ambitious action on climate change, we should not have to live in such a world.

Lisa Benjamin is an associate professor at Lewis & Clark Law School.