How to Think About Climate Change

A Really, Really Long-Term Perspective

For reasons that aren’t altogether difficult to figure out for anyone who experienced this last brutal summer, climate change is a major topic of discussion at the moment. 2023 is now officially the hottest year on record, according to the EU’s Copernicus Climate Change Service. The question of whether we can limit warming to 1.5 degrees Celsius, the internationally agreed target to prevent catastrophic climate change, is up in the air. It’s not looking good: The UN’s Climate Change Conference, COP28, is nearing its end after two weeks of negotiations and firm pushback from OPEC on the issue of phasing out fossil fuels. As hot as this past year has been, it might be the coolest year we experience moving forward, or at least on the cooler side of normal if we look ahead to the next half century.

Climate change isn’t an issue unique to the 21st century. The climate is constantly in flux, on every time scale from years to millennia, every geographic scale from the local to the global. Changes in the amount of sunlight reaching the planet, ocean currents, and atmospheric circulation and precipitation alter the entire Earth: In the past 20,000 years, for example, the Sahara Desert has been an arid region even larger than its current extent, then a green expanse of lakes and savannahs, and now an expanding desert once again. Sea levels rise and fall and rise. Biomes spanning whole continents, such as the Mammoth Steppe (or steppe-tundra) that characterized much of the planet during the last Ice Age, can and do disappear. On the other end of the temporal and geographic scale, volcanic eruptions can destroy a locality or blot out the sun across a hemisphere for a year or two. A single hurricane can ravage a coastline, or warmer and wetter temperatures might render a whole sea far less welcoming to people.

Mammoth steppe: almost nonexistent now, once the most common biome across Eurasia and North America.

We also know that people have been altering their environments for as long as the archaeological record provides us with the right kind of evidence to see it, such as the traces of charcoal left over from burning vegetation. People cut down forests for fuel and building materials. They replace native vegetation with domesticated species. Hunting and habitat destruction drive wild animals to extinction. Intensive agriculture drains the soil of nutrients, and the voluminous waste produced by dense settlements renders whole areas uninhabitable. Like natural processes of climate change, human environmental alteration takes place on a variety of different time scales: immediate, as when we clear-cut a forest; medium-term, as the silting of a river thanks to upstream deforestation resulting in erosion; and long-term, for example, by fundamentally altering the plant and animal species present in an area. Thanks to fossil fuels and the explosion of human populations over the past couple of centuries, our ability to change the whole planet’s climate - anthropogenic climate change - has increased many times over; but the basic idea, that we humans are living in an unstable world that we can and do alter in profound ways, remains much the same.

For what it’s worth, one recent paper argues that the real turning point in our ability to change the planet arrived not with the Industrial Revolution but with the global spread of farming in the Neolithic. By introducing whole suites of domesticated plants and animals, the “Neolithic Multispecies Resettlement Camps” in the words of the anthropologist James Scott, we dramatically increased our scale and impact on the environment. Even a single Neolithic village could profoundly change the local area around it; creating a whole landscape of Neolithic villages altered those environments on a massive scale.

Although these two things - human alteration of our environments and “natural” processes of climate change - might seem to be quite different, they’re united by the fact that we still have to deal with them. The cause of those changes, anthropogenic or natural, isn’t as important as the necessity of figuring out how to respond to them. Human societies deal with both through the same mechanisms, and we’ve been dealing with them for our entire existence.

On one hand, this line of long-term thinking can lead to complacency. If people have been dealing with a changing climate since the very beginning, and we’ve been changing our environments for much if not all of that time, then why bother worrying about it? We’ll get by as we always have before. On the other hand, this reasoning can also lead to a species of doomerism. We’ve changed our environments before, but never on this scale, a scale that can only lead to our destruction of Earth as a habitable planet. Either we get out, becoming multi-planetary, or we’re going down with the ship.

Those are the extreme ends of the spectrum, with a huge variety of viewpoints and possibilities in between. But no matter where one might fall on that spectrum, from apathy to panic, supporting massive intervention to change the trajectory or advocating a completely hands-off approach, it’s worth thinking about how millions of years of our ancestors have dealt with changing climates. Whether we see them as models to emulate or cautionary tales to avoid - and we can find plenty of examples of both in the archaeological and historical records - we ought to see what they have to teach us.

With that in mind, here are a few guiding principles - gleaned from my reading through scholarship covering the past several hundred thousand years of human-environment interactions - that we can usefully apply to thinking about the present.

Humans aren’t simply prisoners of their environments.

People aren’t leaves on the wind, buffeted by environmental forces beyond their comprehension, prisoners of forces we can neither understand nor control. Our species is supremely adaptable - in fact, that’s our most outstanding trait - and we’re smart enough, and resilient enough, to deal with changes as they come up. When short-term or localized changes render an area unusable, we move away to areas that are usable. When long-term changes render a whole way of life (subsistence, patterns of settlement, etc.) unviable, we change that way of life to something that better fits the climatic context. When our habitats are unstable over the short and medium term, we build that instability into our way of life, making it flexible enough to deal with things like extreme El Nino events or rapid shifts in sea level.

It’s never a matter of, well, the climate’s changing, so we’re screwed; instead, we have choices. There was a strong tendency in what I call the first wave of climate scholarship (both historical and archaeological) to look for changes in the past climate record, and to directly correlate those changes with downturns in human societies. If the climate was going bad, the reasoning went, getting colder and drier, then people were obviously going to be in trouble. If you see a volcanic eruption in the climate record in Iceland, then you’re going to see a famine that year or the next in the annals of a northern European abbey. If you’ve got a long drought at the same time as the abandonment of cities, then the drought caused the collapse of that urban society. As it turns out, however, the relationship between changing climate and the fate of human societies doesn’t match lines on a graph. It’s not straightforwardly causal, with shifts in climate causing the downfall of a dynasty or the end of an urban civilization. Causality is a much more complicated thing to figure out.

I’ll focus on one particular example. There was a major aridification event across much of Eurasia and North Africa around 2200 BC, known as the 4.2ka event. Right around that time, Egypt’s Old Kingdom - the age of the pyramid-building pharaohs - came to an end. So did the Akkadian Empire in Mesopotamia, the fruits of Sargon of Akkad and his descendants. The documentary and archaeological record tell us that this was an unstable time across that whole region. People abandoned long-occupied settlements, went on the move, and adopted new lifestyles (more pastoralism, e.g.) in response to these shifts. Established political orders struggled to adapt, and many simply failed.

Yet in South Asia, by contrast, the Indus Valley Civilization (IVC) weathered these climatic shifts just fine, surviving several centuries more before the eventual abandonment of its cities. So far as we know, the climate in South Asia suffered no less than nearby Mesopotamia, but the IVC did not fall apart. The 4.2ka event may have led to more rainfall, not less, in the Alps of Europe. A series of sophisticated late Neolithic societies collapsed in China around that time, the events ranging in time from 2300 BC to 1800 BC, but can we lump all of those processes together into a single climatic event? Even when we zoom in more closely on affected areas, such as Egypt and Mesopotamia, some localities and regions seem to manage just fine without major changes, while others suffered.

The Indus Valley Civilization weathered the 4.2ka event just fine.

Clearly, whatever was happening with a major, well-documented climatic event was more complicated than “when climates change, societies fall apart.” There was a correlation, but the climatic shift interfaced with existing ways of life, modes of thought, and every other process that was happening at the time. That applies across the historical and archaeological record.

Ideas, institutions, and politics shape our responses to climate change.

This follows from the first point. Our options for dealing with changing climates are not endless. The choices we make are conditioned by our understanding of what’s possible and desirable; the mechanisms we have for enacting change; the contingencies of the particular moment, such as who’s in charge and whether or not they’re competent; and how we even understand what’s happening, to name just a few of the almost infinite list of possibilities.

Here’s a thought experiment. You live in a fertile river valley with regular rains and mild floods that replenish the soil and water your crops. That’s been the case for as long as anyone can remember. But then the rains don’t come for two years in a row, and the floods stop, too. Your crops fail, then fail again the following year. You might turn to fishing - after all, there’s a river right there - but how successful are you going to be at fishing if you don’t have an established tradition of catching fish or the technological toolkit to do it well? What if you define your society by farming, by the ownership of particular plots of land and your relationship to the forces of fertility and nature? What if you’re ruled by a clique of shaman-chiefs whose legitimacy derives from their claim to produce good harvests? That climatic shift, the two years of missed harvests, would be far more damaging to the farming society than to a nearby group of foragers who could simply move, or focus their activities on a different food source. One year, they might eat a lot of nuts; in another, hunt a lot of deer; in another, fish the river, gather berries, or go to the coast and look for shellfish.

In this scenario, that hypothetical group of foragers would be more resilient to climatic change than that hypothetical farming society. Rather than being tied to the land and to a limited group of domesticated crops, they could range more broadly and exploit a wider range of resources. Institutionally, their structures of leadership would not be bound up with the harvest, thus rendering decision-making easier and less fraught with conflict in a crisis. In other circumstances, perhaps the farming society would be more resilient, with communal stores of grain and a larger population to weather the band times and absorb losses due to famine and disease. Resilience is a major theme in climate studies, and it can come from a variety of different sources, ranging from methods of subsistence to political institutions to religious beliefs that accommodate and explain natural disasters.

Simply put, it’s hard to predict precisely how a given society will deal with either a short-term environmental disaster or a long-term shift in the climate. Societies that seem remarkably stable and long-lived might fall apart with a feather-light touch of rising sea levels or drought. Simple folk living at the edge of subsistence might starve. Alternatively, sophisticated and stable societies might have the resilience to ride out those initial waves of disaster, collapsing centuries later without an obvious connection to that past climatic event. Simple folk might have the flexibility to alter their way of life and even thrive under the new conditions.

People can be winners, losers, or something in between, but they’re always affected.

Not everybody is going to lose when climatic conditions shift and human environments are destroyed. Hunter-gatherers suffer when their prey animals - mammoths, for example - are driven to extinction, but that creates openings for pastoralists to utilize the landscape for herds of domesticated animals. Pastoralists relying on domesticates suffer when aridification reduces to desert the marginal pasture-land on which they rely, but the lack of grazing animals might allow for large-scale mineral exploration. Rising sea levels might drown coastal plains, but they can also create new wetland environments full of exploitable resources.

Large grazers, such as elephants, suffer disproportionately when people hunt them (because their gestation periods are so tortuously long) and destroy their habitats; but smaller ones, such as deer and boar, thrive in the mosaic environments of intermixed grassland and forest that human intervention tends to create. Societies built on hunting those large grazers would fail, while those oriented around hunting deer and boar would thrive. That’s essentially the story of the transition from the late Pleistocene to the early Holocene, for example, around 12,000 years ago. The same principles apply more broadly. One region might suffer disastrous consequences over the long term because of changes in precipitation and temperature, becoming uninhabitable for its residents. Those same shifts in precipitation and temperature can make another region, the beneficiary of warmer conditions and increased rainfall, dramatically more welcoming and viable.

We can see this clearly in the archaeological record: Patterns of habitation in the landscape vary from era to era, and shifts in local environmental conditions play a significant role in where people decide to live. A region that’s densely populated in one era - the aforementioned Indus Valley of South Asia around 2000 BC, for example - might be nearly deserted 1,000 years later. Conversely, a much less populated area - the Ganges Plain around 2000 BC - might be much thicker with human settlement 1,000 years later.

One region’s, or society’s, or group’s, loss can be another’s gain. Precisely who wins and loses is a function of geography and the patterns of climate change, of course, but it’s also about who the ability to exploit changing circumstances. Ability might mean flexibility in subsistence modes and resilience thanks to kinship networks that distribute help from one family to another. It might also mean having the weapons and the military infrastructure to simply take a more appealing area from its current inhabitants. Even if far more people end up worse off thanks to a climatic shift or environmental destruction - populations drop by half or two thirds and the overall level of social complexity and technological acumen falls - there might still be winners in that scenario: a small group that finds a new ecological niche and expands in numbers, or a new elite that exploits the chaos to establish themselves as rulers.

Should you feel better or worse about climate change and environmental alteration?

I can’t answer that for you. Maybe I’m not telling you anything you don’t already know, or can’t figure out on your own. On the whole, thinking about this issue over the very long term makes me feel more optimistic about the overall survival of humanity as a species. We might kill off 95 percent of us over the course of a couple of centuries of terrible climatic upheaval, and while that would very obviously be a bad thing in any number of ways, we wouldn’t be extinct. That’s a breed of optimism, I suppose, if you stare at it hard enough. At the same time, however, I feel far more pessimistic about the survival of a postmodern, post-industrial way of life, our specific mode of civilization, patterns of urbanism, and everything that goes along with it. Whether we make conscious choices to adapt an unsustainable way of doing things to something more sustainable, or we’re forced to do so by a series of localized disasters and global processes, the historical and archaeological records suggest that we’ll have to make major alterations as conditions change.

That, I suppose, is the major takeaway here: We have some agency - not all the agency, but some - to decide how bad it gets, who suffers and who benefits, whether those changes are preemptive or a reaction to an ongoing catastrophe. The most vulnerable people don’t have to lose everything so that others maintain or improve their standard of living. Life will go on one way or another, because human life goes on no matter what’s happening around us, but it can be better or worse depending on what we collectively decide to do.