How Will We Know the World Is Ending?

Illustration: Elena Scotti (Photos: Shutterstock, Warner Bros.)

Visions of the end of the world tend to extremes—the planet fatally fracked, flooded, hurricaned, nuke-cratered. No survivors, or maybe one or two survivors, dazed and dust-grimed, roaming a wasted landscape, eating canned beans, rotted squirrels, each other. But the truth is we might be in for a slow burn, apocalypse-wise. The “end of the world” entails not just the actual end, that last gasp of human breath, but all the agony leading up to it, too. How, though—without the fire-and-brimstone theatrics—will we know that the planet is truly terminal?


For this week’s Giz Asks, we reached out to a number of experts—in paleobiology, ecology, atmospheric science, geoscience and more—to find out how we’ll know when the world has actually ended. They provided a wide, if uniformly bleak, range of opinions. The end of the world might not mean drowned cities or whole continents aflame—but it probably won’t mean anything pleasant, either.

Jan A. Zalasiewicz

Professor, Paleobiology, University of Leicester

It depends on what world we’re talking about.

The Earth’s a big ball of rock, and it will be here for the next five billion years, until the sun becomes a red giant and in effect blows it up. But it’s a little like Dante’s circles of hell: there are different steps. One world finishes, and an unfamiliar one starts.

The Anthropocene, the proposed new epoch of geological time when humans have come to dominate many processes on our planet’s surface, is based on the end of a particular world, the Holocene world that has been familiar, supportive, comfortable and more or less predictable for basically all of human civilization, up until the 20th century. You could have all kinds of upheavals and scorched-earth wars, but you could always count on nature growing back, on people picking themselves up and starting again on a healing Earth.

With the end of Holocene conditions, much of the familiar world we took for granted is now changing. Climate is clearly changing—we’ve got a trillion tons of extra carbon dioxide in the atmosphere, the Earth is measurably warming, ice is measurably melting, there is beginning to be more sea and less land. And then there are the changes we’re making to the biosphere, largely by replacing more or less natural habitats—forests, savannas, etc.—with urban areas and farmland. We’ve changed the biological landscape around us. Both of these changes are ongoing, effectively permanent, and they’re almost certainly going to intensify before they stabilize again. And that is how the Anthropocene may be viewed, as the end of one world and the beginning of another one. We’re pushing ourselves and the other living organisms with which we share the planet into the unknown.

I used to think this would not affect us in our lifetimes—that it was really going to start being a problem for our children and grandchildren, and that my generation would see things out in more or less familiar conditions. But look at the things like the shrinking of arctic ice, and changing climate patterns, including rising temperatures, as we continue to add another ~20 billion tons of heat-trapping carbon dioxide into the atmosphere each year. Global warming is kicking in already and, yes, I suspect these changes will become really quite noticeable over coming decades. Factor in the unknowns of how society will respond, how the biosphere will react, and how the rapidly growing ‘technosphere’ will evolve, and we may well be in for quite dramatic, and quite challenging times. The new world of the Anthropocene is taking shape rather more quickly than I or many of my colleagues would have thought ten or twenty years ago.

Timothy Morton

Professor of English at Rice University and the author of Being Ecological and Dark Ecology: For a Future of Coexistence, among other books

The very question indicates that the world has already ended. Feelings of unreality or uncertainty are symptoms of trauma. When you’re in a car crash, you wonder whether it’s really happening… The pain of all kinds comes later. “Has global warming really started yet?” is a sign that it has already started, a bit like “I wonder when this acid is really going to kick in.”

“World” just refers to all the stuff you’re into. You are not spatially (“extensionally” as we like to say) “in” a world; you are “into” stuff, and that’s your world(s). The concept implies a reliable background that just churns away as you do your thing. Doesn’t have to be “nature” in particular.

But in ecological terms, the biosphere is no longer reliable. You can’t forget about it. Hurricanes happen in weird scary ways and the mediterranean belt of Earth is bursting into flame. And… we know that there’s no “away.” When you flush the toilet, you know where it goes—into the waste water treatment plant, the ocean or whatever… where it doesn’t go is this magical place called “away.” We now have planetary awareness, whether we like it or not—it’s one of the reasons why there are fascist movements all over Earth... So many extreme right movements in the USA can be traced back to opposition to “Agenda 21” of the United Nations Earth Summit (Rio, 1991), linking antisemitic fantasies about “globalism” with language about biodiversity and international cooperation.

But worlds always have holes in them, because they work for someone, not everyone. Your nice smoothly functioning world is their refugee internment camp.

The world has already ended. You are already dead. This is the afterlife, a.k.a. the beginning of real history when humans finally get to collaborate on a more equal basis with nonhumans.

Your intuition is correct: this is a nightmare. Isn’t that a relief and a fantastic challenge?

Katharine Hayhoe

Atmospheric scientist and professor of political science at Texas Tech University, where she is director of the Climate Science Center

The question exemplifies why it’s so hard for us to wrap our heads around this problem. We can’t conceive of something as big as the end of civilization as we know it, even as an increasing number of dystopian novels and movies paint graphic visions of what it might look like.

It’s not about the end of the planet. The planet has survived much more extreme conditions than this in the past. It’s about the future of human society, which has evolved over just the last ten thousand years or so, during a very narrow range of climate variability.

And just like the proverbial frog—or lobster—in the boiling pot, it’s likely that we may not even realize when we’ve reached points of no return until it is too late.

That’s why I do the work I do, exploring the impacts of a broad range of future scenarios, quantifying what the impact of a two, three, or four degree warming would be on our drought risk, our energy demand, our water supply, and more. Only by understanding the risks we face can we hope to avoid them.


Michael Mann

Distinguished Professor of Atmospheric Science and Director of the Earth System Science Center at Penn State

I imagine we will know the world (by which I mean, a world that can support a human civilization of 7 billion+ people) ended the same way the inhabitants of Easter Island knew they had ended their world. In their case, it was when they cut down the last tree. In our case, it will be when we lose the last mountain glacier, the last major coral reef, the last vestige of summer sea ice in the Arctic, the last low-lying Pacific island nation, and so on. These dominoes will fall one after the other if we continue with our profligate burning of fossil fuels. The choice is ours. We can still avoid this future if we accelerate the transition already underway from fossil fuels toward renewable energy. That requires action from our policymakers and pressure from all of us on them to act in our behalf rather than on behalf of polluting interests.


Seth Baum

Co-Founder and Executive Director of the Global Catastrophic Risk Institute and a Research Affiliate of the University of Cambridge Centre for the Study of Existential Risk

For most global catastrophe scenarios, it ain’t over ‘till it’s over. As long as some humans are still alive, we’ve got a chance to live on and even rebuild civilization. That goes for even the most extreme nuclear wars, pandemics, climate change, volcano eruptions, asteroid impacts, etc. In a few scenarios, humans have no chance of survival, such as some scenarios of runaway AI, alien invasion, and cosmic explosions. However, for these scenarios, we either wouldn’t know in advance that the catastrophe is coming, or we wouldn’t know that everyone would die.

In practical terms, this means that we must be proactive to prevent global catastrophes, because we can’t count on reliable warning signs, and we should also be prepared to survive and recover from any global catastrophes that do occur.


Steven Petsch

Associate Professor, Department of Geosciences at the University of Massachusetts Amherst, whose research involves global-scale carbon cycling and controls on the composition of Earth’s atmosphere over geologic time.

The literal answer to this question from my perspective as a geologist is—the world is not going to end, at least not for many hundreds of millions of years. But if the question is a more human-centered one – “How will we know when Planet Earth has changed enough to affect the natural world as we know it, and by extension our human systems and societies that rely on that natural world?” – that becomes something more real and less academic.

For me, the sign that we’ve lost ‘the world as we knew it’ will be when one of a handful of climate tipping points are crossed. The soonest of these will be the loss of sea ice from the Arctic Ocean during summertime. Throughout human history, the Arctic has been defined as a permanently ice-covered ocean, but the extent of that ice is declining dramatically. For each of the past few years, summertime ice only occupied about 50% of the area it did 30 years ago. It’s not hard to extrapolate from this and predict that in a few decades the Arctic Ocean will be ice-free in summer.

Another soon-to-be tipping point that will show we’ve lost the world as we know it is the loss of coral reefs due to warming and declining pH in surface waters of tropical oceans. These reefs that are so familiar to us as tourist locations, biodiversity hotspots and important fisheries will be a thing of the past, with living reefs replaced by dead coral skeletons devoid of fish. This may happen as soon as mid-century. Small patchy reefs will survive but the massive barrier and fringing reefs that define so many tropical coastlines will be gone.

Unfortunately, these events seem nearly inevitable and without concerted, global-scale action, others will follow. Our human impact on the carbon cycle took decades to set into motion, and it cannot quickly be pushed from its current path. It will take massive wholesale changes in our energy and food production systems to halt or even slow these global changes. In this way, regardless of whether it is tipping points in our natural world or the actions we will to take to mitigate and adapt to climate change, the world as we thought we knew it is over.


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As has been said: there is no one thing, short of a several dozen mile wide asteroid hitting us, that will “end the world” of all life. And even that is just likely a few million-year hiccup before things get rolling again. A full nuclear exchange, while pretty horrifying, wouldn’t even be the end of humanity except in the most specific of terms (something of us will likely make it through no matter what, we’re worse than roaches.). Doesn’t mean it would be anything pleasant to live through though. 1 billion years from now (plus/minus a few hundred million years), when the sun is about 30-40 percent brighter, we’re likely going to go the way of venus. That’s the end of the world in the sense of surface life. But its not until about 4 billion years down the line, when the sun is a red giant, that all the life on earth will be extinguished... as the planet will be consumed by the sun down to the core. That’s the end of the world. That said, its very easy to make life a living hell. Just take a look around, we’re doing it now. So... if the end of the world is measured in personal hardship, pain, and death... then you can see the signs everywhere you go. And the Apocalypse is nigh.