Last year was the hottest year in recorded history. Buckle up.

This story was originally published by Slate and appears here as part of the Climate Desk collaboration

The official numbers are in, and 2024 was the hottest year in recorded history—and almost surely also the hottest year in the history of human civilization.

The meme in which Homer Simpson explains to Bart that what he’s experiencing is the coldest weather of the rest of his life feels apt here. The world keeps getting hotter and hotter; we know that. But this new record is, in fact, additionally terrible. 2024 was also the first year that global temperatures have crossed the 1.5 Celsius degree mark that the world agreed to not cross just 10 years ago in Paris.

To understand why this specific temperature matters so much, let’s rewind a bit: The original goal in the run-up to Paris was to set a line of global warming at 2 degrees Celsius. This was a fairly arbitrary and negotiated benchmark, roughly determined by the upper bound of temperatures scientists think the Earth has ever occupied since humans first evolved millions of years ago. But in 2015, a series of scientific studies—namely one that pointed to the irreversibility of thousands of years of sea-level rise from melting Antarctic glaciers should warming reach 2 degrees—resulted in increasing pressure from small island states and the scientific community. During the Paris conference, the target was set to be more ambitious.

The 2015 Paris Agreement put the world’s nations on record to hold “the increase in the global average temperature to well below 2 degrees C above pre-industrial levels” and pursue efforts “to limit the temperature increase to 1.5 degrees C above pre-industrial levels.” It also commissioned one of the most important scientific studies in history: the Intergovernmental Panel on Climate Change’s Special Report on 1.5 Degrees.

Scientists had been most commonly using the 2 degree mark in their models. The aim of the new study was to understand what exactly would happen if the world warmed beyond 1.5 degrees instead. The results were clear: For millions of people and several irreplaceable ecosystems, like coral reefs, the difference of half a degree of warming would be life-and-death.

Many felt the urgency of keeping warming under this revised target. Greta Thunberg took notice and began her Fridays for Future school strikes. Alexandria Ocasio-Cortez launched the Green New Deal. COVID came, and Joe Biden was elected as the self-proclaimed climate president. As someone who has been covering this stuff for a while, I observed the climate emergency become a mainstream concern in a way it hadn’t ever been before. Many people have in recent years had to confront the reality of climate change firsthand.

Yet we’ve still crossed 1.5 degrees of warming. Where does this stop? Does the world’s attention now shift with equal urgency to stopping the rise at 2 degrees?

The consequences of crossing this line in the sand are profound. The goal of global climate negotiations, after all, is to “prevent dangerous human interference with the climate system.” It’s clear that has already happened. The simple fact is that we set a goal and blew past it—that’s not a great sign that we can work together on climate. There are countless sets of interconnected, interdependent relationships between our planet’s atmosphere, oceans, land, and living things that are constantly being broken and repaired every year, every day.

At some point—more likely than not a point in time we have already passed—these Earth systems will begin breaking on their own. Even though any political target will be somewhat arbitrary, a mix of science and art, that’s the shorthand that 1.5 degrees stands for. And that’s what we’ve now crossed.

Here’s where we’re headed next, if things continue apace: An analysis of the path the world is currently on shows that we’re headed for somewhere between 2.2 and 3.4 degrees of warming. This paves the way for centuries of unimaginable planetary cataclysm.

To me, the real consequence of crossing 1.5 degrees isn’t that any one thing breaks at 1.5 degrees. It’s that we’re slipping away from an era in which the community of nations came together for the common good of humanity—and moving toward an everyone-for-themselves descent into nationalism. It’s that any urgency we’ve felt so far, any actions we’ve taken, hasn’t been enough.

There was an optimism embedded in the Paris Agreement that facts matter and that the discovery of a more worrying set of facts would result in increased efforts to change course as a global community of nations. As we venture further into the era of weaponized misinformation—wielded by some of the exact same people and institutions responsible for the climate emergency—it becomes more and more difficult to imagine climate change rising to the heights of global importance needed to slow and reverse our emissions trajectory.

And yet we can’t lose hope. We’ve gone past the point of no return at the planetary scale, and yet each of our actions still does matter. We have to hold these truths simultaneously in our heads and our hearts and decide how to move forward. If you’re driving into a brick wall at 60 mph, tapping the brake can certainly reduce the impact, even if you can’t prevent the collision.

What this moment demands is for us not to despair. It demands for us to humanize the climate crisis. The response to the fires in Los Angeles, countless firsthand survivor essays of what it feels like to lose a place you love so dearly, is what this looks like. It’s in these moments where it becomes possible to imagine community-scale survival—and even, eventually, joy—in an era of constant environmental challenge. We are living through the climate crisis. We’ve got to do the work of surviving—and we’ve got to do the essential work of building up shared visions of possible futures that are worth fighting for.