For most of its 4.54 billion years, Earth has proven it can manage just fine without human beings. Then came the first proto-humans, who emerged a little more than 2 million years ago—a fleeting moment in geological time. What made it possible? Ironically, it’s the very same thing that now threatens us—climate change.
The drying of the tropics during the Pleistocene period created a niche for early hominids, who could hunt prey as forests gave way to savannahs in the African tropics. The sudden cooling episode known as the Younger Dryas 13,000 years ago, which occurred just as Earth was thawing out of the last Ice Age, spurred the development of agriculture in the fertile crescent. The Little Ice Age cooling of the 16th–19th centuries led to famines and pestilence for much of Europe, yet it was a boon for the Dutch, who were able to take advantage of stronger winds to shorten their ocean voyages.
The conditions that allowed humans to live on this earth are incredibly fragile. Climate variability has at times created new niches that humans or their ancestors could potentially exploit, and challenges that at times have spurred innovation. But there’s a relatively narrow envelope of climate variability within which human civilization remains viable—and our survival depends on conditions remaining within that range.
Climate scientist Michael Mann, director of the Center for Science, Sustainability and the Media at the University of Pennsylvania, examines the knowledge necessary to appreciate the gravity of the unfolding climate crisis, while emboldening us to act before it becomes too late.
Mann’s book Our Fragile Moment: How Lessons from Earth's Past Can Help Us Survive the Climate Crisis (PublicAffairs) is available for purchase