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News — In 2016, nearly 200 world leaders pledged to do everything possible to limit global warming to 1.5 degrees Celsius. Since then, policymakers across the globe have designed countless laws around the assumption that warming would never cross that threshold.

But scientists have some sobering news to share: Earth exceeded 1.5 degrees of warming in 2024, it’s hurtling fast toward even more warming, and it has already changed in irreversible ways.

According to research , even if every country kept its current Paris Agreement pledges—and that’s a big if—the globe will still be on course to warm 2.7 degrees Celsius, or 4.9 degrees Fahrenheit, by the year 2100.

“This is a reality check: We took a first step by signing the Paris Agreement, but we’re already living in the ‘changed world’ we are attempting to prevent,” said Regents’ Professor of Ecosystem Ecology Ted Schuur of Northern Arizona University, one of the study’s authors. “Even with the ambitious goals we set and the stricter emissions policies we have in place, we will still end up with a planet that has warmed at least 2.7 degrees. It’s time to take the next step to adjust our climate goals to accommodate this new reality.”

Why did we pass 1.5 degrees of warming so much sooner than we imagined? It’s partly to do with what’s happening above the Arctic Circle, Schuur said.

A changed cryosphere 

Research summarized by Schuur and his colleagues shows that the Arctic is warming nearly four times faster than the rest of the world. Why? Because its frozen surfaces are melting. 

Take sea ice, for example. Before current global warming, the Arctic Ocean would reliably freeze over in the winter and partially melt in summer. But now that the globe has surpassed 1.5 degrees of warming, a greater portion of winter ice melts with every passing summer, leaving more and more ocean exposed through late fall. That accelerates warming because dark-colored ocean water absorbs more sun than light-colored ice sheets.

“The Arctic seas have already become unrecognizable,” Schuur said. “The amount of ice we’re left with at the end of the summer keeps declining over time. Soon enough, summer ice could become a thing of the past”—changing the lives of people who live in the region, opening up new shipping routes and, undoubtedly, unleashing new international relations quagmires. 

On land, warming is affecting the Arctic no less dramatically. As temperatures increase, huge swaths of ground that were underlain by permafrost are thawing, releasing long-sequestered carbon into the air as greenhouse gases. Scientists have predicted that as warming continues, this decomposing organic matter will release amounts of carbon dioxide and methane that are comparable to the carbon emissions of large industrialized nations. 

Unfortunately, Schuur said, these phenomena didn’t factor adequately into policymakers’ calculations in 2016.

“We’re talking about a place that’s remote to many people, but changes in the Arctic don’t stay in the Arctic,” he said. “Once we lose that ‘freezer’ of organic material, it turns into greenhouse gases that go into the atmosphere and accelerate warming. Last summer, Phoenix had 70 days with temperatures over 110. That’s mainly due to human greenhouse gas emissions, but it was accelerated in part due to additional greenhouse gases from the Arctic.”

Adapting to a warmer world

Schuur said it’s now clear that current policy targets will warm the globe 2.7 degrees by the end of this century, creating an even warmer world than the one we are experiencing today. It’s now our collective task to make communities more resilient to the inevitable change ahead and try to reduce further human greenhouse gas emissions.

“We can’t stop change from happening; it’s already happening,” Schuur said. “But we can slow the change by reducing greenhouse gas emissions and managing the change as best as we can so that people and ecosystems are better positioned for the future.”

Schuur encouraged people to get involved in their city, county or state sustainability efforts, as those can be more direct. Involvement could mean attending civic meetings or bringing new policy ideas to leaders, or it could simply mean supporting sustainability measures by voting in local elections.

He also advised people to keep taking individual action. In the face of bad news, it can seem like your electric car, solar panels and reusable mug aren’t making a difference. Schuur explained that those choices may not halt warming in its tracks, but they still help slow the rate of warming. 

“Don’t give up, even in the face of change,” Schuur said. “Instead, change your thinking. Say to yourself: I live in a new, changed world. What can I do to help adapt and slow the change so we have more time to adjust?”