Holocene

Based on Wikipedia: Holocene

You are living in a geological accident. About 11,700 years ago, the ice retreated, the seas rose, and the planet entered a brief warm spell between glaciations. We call it the Holocene—from the Greek words meaning "entirely new"—and everything humans have ever built, written, or remembered has happened within it.

Every city. Every empire. Every war and every poem. The pyramids, the printing press, the internet. All of it fits inside this narrow window of mild weather, a mere eyeblink in Earth's four-and-a-half-billion-year history.

The Warm Pause Between Ice Ages

Here's the thing most people don't realize about our current era: it's not normal. For most of the past few million years, Earth has been locked in repeating cycles of glaciation—ice ages that bury continents under kilometers of frozen water, punctuated by brief warm periods called interglacials. The Holocene is one of these interglacials. It's a pause, not an ending.

The ice ages haven't stopped. They're just taking a break.

This becomes clearer when you look at the bigger picture. The Holocene and the epoch before it, the Pleistocene, together form what geologists call the Quaternary period—essentially the "Ice Age era" that began about 2.6 million years ago. During the Pleistocene, massive glaciers advanced and retreated dozens of times, reshaping continents, carving out the Great Lakes, and periodically making places like New York and London uninhabitable under miles of ice.

Then, around 11,700 years ago, the most recent glacial period ended. Different regions have their own names for this last freeze: North Americans call it the Wisconsinan glaciation, Europeans know it as the Weichselian, and the British refer to it as the Devensian. Whatever you call it, when it ended, the Holocene began.

A World Transformed by Melting Ice

The transition wasn't subtle. As the glaciers melted, they released staggering amounts of water. Sea levels rose about 35 meters—roughly 115 feet—in the early Holocene alone, then another 30 meters later. To put that in perspective, that's enough water to flood every coastal city on Earth many times over.

But the changes went far beyond rising seas. In the northern latitudes, where glaciers had pressed down on the land for tens of thousands of years, the earth itself began to bounce back. This process, called post-glacial rebound, is still happening today. Scandinavia is rising so quickly—in geological terms—that it still causes weak earthquakes across Northern Europe. The Gulf of Bothnia between Sweden and Finland was once a much larger sea; it's been shrinking ever since the ice left.

The same thing happened in North America. Hudson Bay was once the Tyrrell Sea, a much larger body of water left behind by the retreating glaciers. As the land rose, the sea shrank to its current size. Some areas have bounced back by as much as 180 meters—nearly 600 feet—since the ice melted.

This combination of rising seas and sinking-then-rising land created temporary marine invasions into places that seem impossibly landlocked today. Geologists have found Holocene marine fossils in Vermont and Michigan—evidence of ancient seas that briefly flooded these regions before the land finished rebounding.

Three Ages Within an Age

In 2018, the International Union of Geological Sciences—the organization that serves as the official keeper of Earth's timeline—decided to slice the Holocene into three distinct ages. Each marks a dramatically different climate regime.

The oldest is the Greenlandian, lasting from 11,700 to 8,200 years ago. Named for the Greenland ice cores that help define it, this was the warming phase—the planet shaking off its glacial chill and entering the balmy conditions that would make human civilization possible.

Then came the Northgrippian, from 8,200 to 4,200 years ago. This age saw a dramatic cooling event triggered by one of nature's more counterintuitive phenomena: the melting glaciers actually made things colder. As vast quantities of fresh meltwater poured into the North Atlantic, they disrupted the ocean's circulation patterns—the great conveyor belts of warm and cold water that regulate global climate. The result was a significant cooling across much of the Northern Hemisphere.

The most recent age, and the one we're living in now, is the Meghalayan. It began 4,200 years ago with a catastrophe: a drought so severe it lasted roughly 200 years. This wasn't just bad weather. Archaeological evidence suggests this mega-drought contributed to the collapse of civilizations from Egypt to Mesopotamia to China. The Old Kingdom of Egypt fell. The Akkadian Empire crumbled. And somewhere in a cave in the Indian state of Meghalaya—for which this age is named—chemical signatures in stalagmites recorded the shift in rainfall patterns that define the boundary.

The Holocene Climatic Optimum (And What Came After)

If you could pick any time in the Holocene to live—assuming you wanted warm weather and didn't mind a complete absence of modern medicine—you'd probably choose the Holocene Climatic Optimum. This was a period of unusual warmth that peaked at different times in different places, generally somewhere between 9,000 and 5,000 years ago.

During the optimum, global temperatures were somewhat warmer than pre-industrial levels. The Arctic was warmer than today. Forests grew farther north. And the Sahara—yes, that Sahara, the world's largest hot desert—was a savanna dotted with lakes.

This wasn't a subtle difference. During what's called the African Humid Period, North Africa received so much more rainfall that it supported large lakes, extensive vegetation, and thriving communities of pastoralists who herded cattle across what is now endless sand. The Intertropical Convergence Zone, that band of atmospheric circulation that determines where tropical rains fall, had shifted northward, bringing monsoons deep into what is now the Sahara.

Then, around 5,500 years ago, it ended. The convergence zone shifted south again, the rains stopped, and the green Sahara began its transformation into the desert we know today. This wasn't a gradual change—in geological terms, it was remarkably abrupt.

After the Holocene Climatic Optimum, the planet entered a long, slow cooling trend called Neoglaciation. For several thousand years, temperatures gradually declined. Glaciers that had retreated began to advance again, though not nearly to their previous extent. This cooling trend continued, with various fluctuations, until the Industrial Revolution changed everything.

Medieval Warmth and the Little Ice Age

The last thousand years brought two particularly notable climate swings. First came the Medieval Warm Period, roughly from the 10th to the 14th century. During this time, Vikings colonized Greenland and briefly settled in North America. Wine grapes grew in England at latitudes where they can barely survive today. Civilizations from Europe to China enjoyed what seems to have been an era of relatively benign weather.

But here's the important caveat: the Medieval Warm Period wasn't uniformly warm everywhere. Unlike modern warming, which is remarkably consistent across the globe, medieval warmth was patchy and regional. Some areas warmed significantly; others barely noticed. Scientists have found that the kind of warming we're experiencing today—uniform, global, and persistent—occurs five to forty times more frequently in the modern era than during the Medieval Warm Period.

The difference comes down to what's driving the warmth. Medieval warming was primarily caused by increased solar activity—the sun was simply putting out slightly more energy. This creates uneven warming because different parts of Earth's surface respond to solar changes in different ways. Modern warming, driven by greenhouse gases that trap heat throughout the atmosphere, is far more homogeneous.

The Medieval Warm Period ended, and what replaced it was dramatically different: the Little Ice Age. From roughly the 13th or 14th century through the mid-19th century, the planet cooled significantly. The Thames froze regularly enough that Londoners held "frost fairs" on the ice. The Norse colonies in Greenland died out. Glaciers advanced across Europe, swallowing farms and villages that had existed for centuries. The Little Ice Age was the coldest interval of the past two thousand years.

The Fingerprints of Humanity

There's something unusual about the Holocene compared to previous interglacials: it hasn't cooled as much as it should have.

Looking at previous warm periods between ice ages, scientists would expect to see a more pronounced cooling trend by now. Instead, the Holocene has maintained relatively stable temperatures—and some researchers believe humans are the reason why.

Even before the Industrial Revolution, people were reshaping the planet in ways that affected climate. The spread of agriculture cleared vast forests, releasing carbon dioxide. Rice paddies produced methane. The land-use changes that began with early farmers may have been just enough to counteract natural cooling trends that would otherwise have pushed us back toward glaciation.

This idea remains debated, but the underlying point is incontrovertible: humans have been geological forces for far longer than we usually assume. By the Mesolithic—the middle stone age, before the development of agriculture—human activity was already having major ecological impacts.

In the French Alps, for instance, scientists studying lake sediments have traced the gradual development of soil from the last ice age through the Holocene climatic optimum. Then something changed. As human societies settled the region, deforestation and agriculture began accelerating erosion. By the Middle Ages, humans had become the dominant force shaping the landscape—more powerful than climate, geology, or any natural process.

The Proposed Anthropocene

All of which brings us to a question that geologists spent fifteen years debating: should we declare that the Holocene has ended and a new epoch, the Anthropocene, has begun?

The term was coined in 2000 by atmospheric chemist Paul Crutzen and biologist Eugene Stoermer. Their argument was straightforward: human activities have become so dominant that they're leaving permanent marks in the geological record. Future geologists digging through rock layers will find a sharp boundary—plastics, radioactive isotopes from nuclear tests, nitrogen from artificial fertilizers, the sudden extinction of countless species—that clearly marks "before" and "after" humanity's transformation of Earth.

A working group spent years studying the proposal. In 2019, they voted in favor of recognizing the Anthropocene as a formal geological unit, with its starting point around the mid-twentieth century—specifically, the signatures left by nuclear weapons testing beginning in 1945.

But in March 2024, the proposal was rejected. The Subcommission on Quaternary Stratigraphy voted it down by a wide margin, and the decision was later confirmed by the International Union of Geological Sciences with near-unanimous agreement.

The reasons were largely technical. Geological epochs are defined by layers of rock laid down over thousands or millions of years. The proposed Anthropocene would have begun less than a century ago—barely a blink in geological time. The sedimentary record is too shallow, the starting date too recent. It wasn't that the scientists doubted human impact on the planet; it was that fitting that impact into the framework of geological time proved more difficult than proponents had hoped.

So we remain in the Holocene—specifically, in the Meghalayan Age of the Holocene Epoch of the Quaternary Period. The unofficial "Age of Humans" continues under its official name: the "entirely new."

Living in the Interglacial

Understanding the Holocene means understanding something uncomfortable: our entire civilization exists because of a temporary warm spell in an ongoing ice age.

The glacial cycles haven't stopped. Based on orbital patterns—the slight wobbles in Earth's tilt and orbit that have driven ice ages for millions of years—we would eventually expect another glacial period, another advance of the ice. The only question is when.

Ironically, human-caused climate change may have postponed this indefinitely. By pumping greenhouse gases into the atmosphere, we may have interrupted the natural cycle entirely. Whether that's a disaster averted or a disaster in the making depends entirely on how much warming we cause and how quickly.

But that's a story for another epoch—whichever one comes next.

For now, we live in the Holocene: 11,700 years of unusual warmth, 11,700 years in which humans went from scattered bands of hunter-gatherers to a species that has touched every corner of the globe and reshaped it in our image. All of recorded history—every scroll and book, every monument and ruin—fits within this geological instant.

The name means "entirely new." And in a sense, it still is. We're still figuring out what this warm window means, what we've done with it, and what comes after. The glaciers retreated. We built everything. The story continues.