Hulton Archive; Adam Maida / The Atlantic

The COP26 international climate-change negotiations have just begun in Glasgow, Scotland, and the vibes are … ambivalent. The leaders of Russia and China haven’t bothered to attend, but did promise to help end deforestation by 2030—though many observers are skeptical that they will keep their word. In the United States, President Joe Biden’s “Build Back Better” plan lost a powerful provision that would have helped convert the nation’s electricity grid to renewable energy, but still includes an unprecedented $555 billion to combat climate change.

In a prelude to the conference, the UN added up the most recent pledges of parties to the 2015 Paris Agreement. If all 192 keep their promises, the synthesis found, the planet would still be on track to warm 2.7 degrees Celsius, or 4.9 degrees Fahrenheit, by the end of the century. This is nearly twice the 1.5-degree-Celsius (2.7 Fahrenheit) goal agreed to in principle in Paris. But it is also not nearly the jump predicted in the hottest scenario envisioned in the latest report by the Intergovernmental Panel on Climate Change—4.4 degrees Celsius, or 8 degrees Fahrenheit.

The world is wandering into a kind of gray area between total failure and real global commitment to containing global warming. In a recent video call to supporters, Varshini Prakash, the head of the Sunrise Movement, which advocates for aggressive action on climate change, said she felt two ways at once—proud “that we forced Democrats and the president to care about our generation” and also angry.

“I feel disappointed that this is all that we’ve won,” she said.

It is hard to know how to feel. A future of possibly 5 degrees Fahrenheit of warming seems like an unknown country. Is it a civilization-ending crisis? Or is it a more familiar version of awful—a bit sweatier, more chaotic, and less just than the world we currently inhabit?

More in this series

Brian O’Neill, the director of the Joint Global Change Research Institute, a partnership between the U.S. Department of Energy and the University of Maryland at College Park, has a clearer view of this question than most of us. He was one of the lead architects of the five different futures—called “shared socioeconomic pathways,” or SSPs—developed for the latest IPCC report.

These five futures aren’t just versions of 2100 at different temperatures. Each started with a different idea about how society might develop. The SSP 1 pathway, which keeps us under that 1.5-degree-Celsius goal, for example, is the “Sustainability” path. In this scenario, the global economy still expands, but humanity “shifts toward a broader emphasis on human well-being, even at the expense of somewhat slower economic growth over the longer term.” The highest-temperature scenarios are SSP 4, in which inequality accelerates to even more grotesque levels, but advanced technology zaps some emissions, and SSP 5, where the world simply charges forward with fossil-fuel-powered turbo-capitalism.

The path we seem to be on, at least for now, looks closer to SSP 2, which the authors call “Middle of the Road.” This is a world in which “social, economic, and technological trends do not shift markedly from historical patterns.” A world, in other words, in which we do not heroically rise to the occasion to fix things, but in which we also don’t get much worse than we already are.

So what does this SSP 2 world feel like? It depends, O’Neill told me, on who you are. One thing he wants to make very clear is that all the paths, even the hottest ones, show improvements in human well-being on average. IPCC scientists expect that average life expectancy will continue to rise, that poverty and hunger rates will continue to decline, and that average incomes will go up in every single plausible future, simply because they always have. “There isn’t, you know, like a Mad Max scenario among the SSPs,” O’Neill said. Climate change will ruin individual lives and kill individual people, and it may even drag down rates of improvement in human well-being, but on average, he said, “we’re generally in the climate-change field not talking about futures that are worse than today.”

But all the current physical impacts of climate change—drought, extreme heat, fire, storms, sea-level rise—would get significantly worse by 2100 under SSP 2. And say goodbye to coral reefs. “At 2.5 degrees [Celsius], it’s probably a world in which we don’t have them,” O’Neill said. “They don’t exist.” The Arctic? “My guess is that we would have a permanently ice-free Arctic in the summer. And so we would have all of the ecological consequences that would come along with that.”

All the IPCC scenarios might be wrong. They’re using statistical extrapolation and models, and as O’Neill reminded me, history is always wilder than people expect. (Just as Mad Max scenarios are missing from the SSPs, so are “no growth” scenarios.) But the world we are heading toward may be one in which the average human is living longer and making more money than ever, but some vulnerable humans and many nonhumans are collateral damage.

This is why many climate activists frame global warming as a problem of justice.

John Paul Jose is a young climate activist based in Kerala, India, where a series of flash floods linked to climate change have killed hundreds of people since 2018. “In all seasons throughout the year, there is cyclones, extreme rainfall and flood, heat waves,” he says. “And the place where I live is an ecologically fragile and sensitive hill, an extension of Western Ghats. The immediate danger we have is of landslides and flooding in low-lying areas. So anything could happen in future; the only thing is to live in fear and hope.” He wants to see drastic emissions cuts promised at COP26, along with serious money flowing from rich countries that have historically emitted the most toward poor communities where the impacts are the worst. At COP16, in 2010, wealthy nations promised to send $100 billion a year to “developing countries” by 2020, but Oxfam International estimates that climate-specific net assistance is currently more like $20 billion a year.

Climate advocates like Leah Stokes, a political scientist at UC Santa Barbara and an adviser to congressional Democrats on climate policy, are determined to find a way through this gray area. For her, the action that is happening is a motivation to push for even more action. “If they are able to pass this bill, it won’t just be okay; it will be transformative,” she told me. But there’s more to do after the celebrations. “The climate crisis is not going to be solved in one bill. Every ton matters. Every dollar we get invested in this matters. It all adds up,” she said.

Fighting for incremental investment dollars is not as dramatic as a single sweeping intervention to avoid total planetary ruin, and activists moved by horrific visions of human extinction may not be as motivated by the quest to steer the globe from SSP 2 to SSP 1, to shave just a few degrees off the total average warming. But anyone who needs an apocalypse to focus on can rest assured that it’s happening, unequally, for some. Even at today’s 1 degree Celsius (1.8 degrees Fahrenheit) of warming, for many individual people, communities, and species, climate change has already meant the end of their world.