By Blake Wells
In last month’s Third Act PA newsletter, we gained an appreciation of our place in Earth’s geological history with a review of Timefulness: How Thinking Like a Geologist Can Save the World. Continuing this theme, we consider climate scientist Michael Mann’s book Our Fragile Moment: How Lessons from Earth’s Past Can Help Us Survive the Climate Crisis. Mann is one of the creators of the famous hockey stick chart. This graph, depicting global temperatures over the last 2,000 years, is an icon in the fight against climate change. The chart, appearing in United Nations climate assessments, shows that the global warming we’ve experienced in the last 50 years is a sharp break from the stable temperatures over the last 2,000 years. However, in Our Fragile Moment, Mann traces Earth’s changing climate over its entire history and goes beyond the chart to reveal that the current warming exceeds anything experienced in the last hundred millennia. As Mann says, “Let that sink in.”
Mann traces Earth’s climate from when it formed 4.55 billion years ago up to the present era. In this timeline, it’s humbling to conceive that modern humans emerged only 200,000 years ago, and human civilization has existed for just 6,000 years. During this “fragile moment,” prior to the hockey stick’s upward spiking blade in the 1970’s, the climate has been remarkably stable and has provided conditions for humans to thrive. This stability has been maintained by self-reinforcing mechanisms that resist changes to the climate. However, Mann warns that pushing the climate system too much through the burning of fossil fuels will disrupt these mechanisms and trigger new ones that will destabilize our climate.
Mann’s book describes Earth’s climate resilience, detailing one example 4 billion years ago when high levels of greenhouse gases provided temperatures warm enough for life despite the Sun being 30% dimmer than it is today—the Faint Young Sun paradox. He also delves into destabilizing mechanisms, like a “Snowball-Earth” episode 2 billion years ago in which photosynthesis caused a rapid increase in oxygen that cannibalized atmospheric methane, resulting in an ice-covered Earth. These examples inform us about the climate-disrupting tipping points seen today, such as the slowdown — and resulting impacts — of the ocean conveyor belt (AMOC), a future including worst-case rising sea levels of 6.5 feet by the end of the century, and the US East Coast suffering a Superstorm Sandy event every few years. With business-as-usual climate policies, Mann warns of warming as much as 5.4ºF, resulting in “…a lot of suffering, species extinction, loss of life, destabilization of societal infrastructure, chaos, and conflict. An end, perhaps, to our fragile moment.”
Mann emphasizes that uncertainties in climate models, often cited by climate-change deniers, are reasons for more action, not less. At this stage of the climate debate, he says, the larger issue isn’t climate denialism but doomism—the idea that it’s too late to ameliorate the worst effects of climate change. On the contrary, his analysis concludes that limiting these impacts is still entirely within our power both physically and technologically. The problem is politics.
For a fascinating glimpse of how Earth’s climate history informs us of the possibilities of our future climate, I highly recommend this book’s rigorous yet readable treatment of this topic.