It was the climate movement’s unifying slogan for the past decade: “Keep 1.5 Alive.”
The tagline referred to the central ambition of the 2015 Paris climate agreement, in which almost every country pledged to try to limit global warming to 1.5 degrees Celsius.
Now, just 11 years after the target was set, 1.5 is effectively dead.
Scientists now say that without drastic efforts to reduce greenhouse gases, it is very likely that the planet will warm at least 2.6 degrees Celsius, or 4.7 degrees Fahrenheit, by the end of the century.
At COP31, the United Nations climate summit in Antalya, Turkey, diplomats who spent so long championing the 1.5 degree target lamented the abrupt setback.
“The world has no chance of holding to 1.5 degrees,” said Chris Bowen, Australia’s minister for climate change and energy, who is leading the negotiations.
Scientists for years have warned that allowing global average temperatures to rise 1.5 degrees Celsius, or 2.7 degrees Fahrenheit, above preindustrial levels would result in a profoundly more dangerous world. Extreme heat will become more common and more intense. Storms will become more powerful and destructive. Sea levels will rise. And poor countries will bear the brunt of the damage.
That scenario is already playing out around the world. In recent months, wildfires have raged from Canada to Indonesia. The collapse of a glacier in Nepal killed thousands and wiped away towns. Floods and mudslides devastated Brazil. And a European heat wave killed an estimated 50,000 people.
In the face of this mounting destruction, one lingering question at the climate talks was what would be the new goal, if any, as the world overshoots the 1.5 benchmark.
“We don’t think that there’s a new target,” said Ilana Seid, Palau’s ambassador to the United Nations. “We still have a Paris Agreement target of 1.5, and so we are still continuing to say that’s the target.”
Rachel Cleetus, director of the climate program at the Union of Concerned Scientists, warned against fixating on a new target, saying instead that it was important to confront what breaching the threshold has wrought.
“I don’t think it’s a question of replacing 1.5,” she said. “There is no new number. We are now in the unsafe zone.”
Leaders rejected the idea of resetting the goal to 2 degrees Celsius or even 2.5 Celsius, saying that allowing for endless revisions created a slippery slope that could make progress harder to achieve.
While world leaders acknowledged they had missed the target, they also said it might still be possible to get back to 1.5 degrees of warming.
The United Nations secretary general, António Guterres, called on countries to redouble efforts to reduce greenhouse gas emissions with the aim of limiting additional warming, and ultimately turning down the Earth’s thermostat.
“The truth is that we have the power to determine how high, how long and how devastating that overshoot will be,” he said. “We have the power to make sure the overshoot is a temporary breach, not a permanent sentence.”
In order for warming past 1.5 degrees to be temporary, humans would have to figure out how to lower concentrations of greenhouse gases in the atmosphere.
That won’t be easy. Emissions continue at near-record levels. Finding a path back to 1.5 degrees would require the world to drastically reduce the burning of fossil fuels like coal, oil and gas.
Although clean energy is growing rapidly, the world is expected to continue to use fossil fuels for decades to come.
Because reducing emissions is proving so difficult, some environmentalists and scientists are proposing different types of geoengineering, including large-scale carbon capture and storage or attempts to reflect the sun’s energy away from the planet by injecting particulate matter into the stratosphere.
“Overshoot must be kept as small and short as possible, and be rapidly reversed,” said Hilda Heine, president of the Marshall Islands, an island nation threatened by sea level rise. “We have fallen short of the emissions reductions needed to stay under 1.5. We must rewrite the future.”
Lisa Friedman and Chico Harlan contributed reporting.
Three questions for Gavin Newsom at COP31
Your newsletter host, David Gelles, spoke to the California governor on the sidelines of the climate summit in Turkey.
What can Democrats in Congress do on the climate front while President Trump is still in office? And what about House Resolution 1, the 2025 budget law that cut clean energy incentives?
I hope the Democrats make this part of their 100-day agenda. That it’s not just rolling back the worst cuts under H.R. 1, that we focus on restoring a lot of the good work that was done during the Biden administration under the I.R.A. and restore a lot of those cuts. Restore a lot of the cuts that were done environmentally in the infrastructure bill that was rolled back by the Trump administration. The clean energy subsidies and tax credits, the work on wind in particular that’s been attacked by the Trump administration, that should all be front and center on our agenda.
Do you think Democrats need to find new ways to talk about climate issues?
You can use different language, and that’s why I talk about places, lifestyles, traditions. That’s why we talk about extreme heat. That is why we have the extreme heat index in California. That is why we talk about climate risks and financial risks. Why we talk insurance markets. Why we just spent the day talking about wildfires and the impacts they’re having on our communities. So I think it’s our language, and for me the number one issue is the strategic imperative now to focus on this transition.
Any thoughts about 2028?
We’ll see. I mean, I still haven’t made a decision, so we’ll see how it all processes and plays out. But it’s all got fast-tracked. That was inevitable in some ways, unsurprising. But I think you’re going to start to see two or three debate stages set up in May and June of next year. And it’s already taking shape. It’s going to be fast.
Following a father’s Antarctic dream
Max Worsley grew up steeped in his father’s love for Antarctica. But when Henry Worsley died in 2016, he left behind an unfulfilled promise: that the two of them would one day trek across the continent together. This month, Max finally set out into the lonely expanse his father loved, to finish the journey on his own. — Raymond Zhong
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